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Ajman University of Science & Technology
Faculty Of Pharmacy & Health Sciences

.………………….

LABORATORY MANUAL FOR
INTRODUCTION OF PHARMACY

Central Committee
Department of Pharmaceutics

…………………..
2000 - 2001
Dear Students,

The central committee of department of pharmaceutics, Faculty
of Pharmacy and Health Sciences, is pleased to introduce to you the
Laboratory Manual of Introduction of Pharmacy (700111). The
manual covers experiments deal with the principles discussed in
didactic lectures. These experiments employ fundamental principles
of handling prescriptions of non-sterile pharmaceutical solutions of
both aqueous and non-aqueous preparations. The central committee
set this manual for all the branches to ensure the uniformity of
student outcome.

Best Regards

Central Committee
Department of pharmaceutics,
Faculty of Pharmacy and Health Sciences

2
Table of Contents

Part Content Page
No. No.
Part 1 Accuracy in Measurement

Introduction 6
How to use class A Prescription Balance
Exp. (1) Test the Prescription Balance 15
Determination of Tablets Weight Variation

Exp. (2) Aliquot and Geometric Dilution Method 20

Part 2 Concentration and Dilution

Intoduction 23
Exp. (3) Preparation of solution with given concentration 25
Exp. (4) Dilution of Stock Solution 28

Part 3 Pharmaceutical Solution

- Introduction 31
Exp.(5) - Aqueous Solution 32
- Aromatic Water
 Preparation of Double Strength Chloroform Water
 Preparation of Strong Sodium Salicylate Mixture
 Preparation of Peppermint Water

Exp.(6) - Solution for Internal use 38
 Preparation of Pot. Iodide Expectorant Solution
- Solution for External use
 Preparation of Aqueous Iodine Solution

Exp.(7) - Viscous Aqueous Solution (Syrups) 40
 Preparation of Simple Syrup
 Preparation of Acacia Syrup
Exp.(8)  Preparation of Cough Syrup 41
 Preparation of Cough Syrup for diabetic

3
Exp.(9) - Non-Aqueous Solution 43
- Aromatic Elixir
- White Liniment B.P.C.

Exp.(10) - Glycerites 48
 Preparation of Sod. Bicarbonate ear drops
 Preparation of Starch Glycerol ear drops
- Lysol

Part 4 Isotonic Solution

Introduction 52
Exp.(11)  Preparation of Pilocarpine Ear Drops 53
 Preparation of Isotonic KCL Solution contains 10 mEq.
Appendix  Common Abbreviations 56
 Approximate Practical Equivalents
 International System of Units

4
Part 1

ACCURACY IN MEASUREMENTS

5
INTRODUCTION TO MEASUREMENT SYSTEMS

Two of the most crucial steps in compounding any pharmaceutical product are
the accurate calculation and measurement of the component ingredients of the
formulation. In order to carry out these critical functions, the pharmacist must have a
working knowledge of three systems of measurement: the Metric system, the
Apothecary system, and the Avoirdupois system.

THE METRIC SYSTEM

The metric system is the preferred and most frequently used system of
measurement in pharmacy. Since it is a decimal system, other denominations of
measure in the system are easily and quickly generated as a 10nth multiple at the basic
unit. To convert from larger to smaller units, one need only move the decimal the
appropriate number of places to the right. The decimal is moved to the left to convert
from smaller to larger units.

THE APOTHECARY SYSTEM

The Apothecary system was commonly used in the past by pharmacists and
physicians as the system of weights and measures for prescribing and dispensing
medications. Although it has largely been replaced by the less cumbersome metric
system, the pharmacist still encounters these symbols in his/her routine practice. Indeed,
the apothecary system of fluid measure is still commonly used in a variety of products,
both pharmaceutical and nonpharmaceutical, and everyone should be familiar with the
fluid ounce, pint, quart, and gallon.
Since quantities of ingredients in the Apothecary system are commonly written in
Roman rather than in Arabic numerals, you should recall the following:
ss or ss = 1/2 L or l = 50
I or i = 1 C or c = 100
V or v = 5 D or d = 500
X or x = 10 M or m = 1000

THE AVOIRDUPOIS SYSTEM

The Avoirdupois system is a system of weight measurement only. Its basic unit,
the grain, is the same as in the Apothecary system. The Avoirdupois ounce and pound
differ in weight and symbols from those in the Apothecary system. The Avoirdupois
pound is the pound to which we are all accustomed in our daily lives. It is also the
weight measure in which bulk chemicals and over the counter pharmaceuticals are
bought and sold. It is important to make this distinction from weights in the Apothecary
system, which are used only in the prescription or medication order.

6
INTRODUCTION TO WEIGHING

It is generally agreed that pharmaceutical products should be prepared with a low
percentage of error. The official compendia allow a tolerance of ± 5% for most
formulas, although greater accuracy may be required for very potent drugs with greater
toxicity potential. This same degree of accuracy is expected in all extemporaneously
compounded products.
Most pharmaceutical products allow for a tolerance of only 5% error, where

If we know the sensitivity of the balance (i.e. the potential error) we can calculate the
percentage of possible error when any amount of the substance is weighed.

e.g. The Class A prescription balance has a sensitivity of 6 mg. What % of error would
result in weighing 50 mg of a drug on the balance?

Similarly, we can calculate the smallest quantity that can be weighed, on a balance of
known sensitivity, to maintain a desired level of accuracy. This weight is referred to as
the least weighable quantity (L.W.Q.)

7
You should keep this figure in mind for the remainder of your career. When a
prescription formula calls for the incorporation of a component weighing less than 120
mg, special methods must be employed to obtain that weight of the component. If a
liquid dosage form (solution, suspension or emulsion) is being prepared, the liquid
aliquot method is employed. When the component must be incorporated as a solid into
powders, tablets, capsules, or pastes, the trituration method is used.

THE CLASS A PRESCRIPTION BALANCE

Most pharmacists will make their weight measurements on a Class A prescription
balance. In fact, pharmacies are required by law to have such a balance in their facility.
Hence, it is important to understand the limitations of this balance so that you can use it
properly to maximize dosing accuracy.
The Class A Prescription Balance is a 2-pan torsion type balance, which utilizes
both internal and external weights. Although extremely durable and relatively simple to
use and maintain, the balance is less sensitive than the analytical balances you have
probably used in the past. The Class A Balance has a sensitivity requirement of 6 mg,
meaning that as much as 6 mg could be added to or removed from the pan before the
balance marker will move 1 division

BALANCE WEIGHTS

A proper set of metric weights (Class C or better) is essential for prescription
compounding. These sets usually contain cylindrical weights ranging from 1-50 g and
fractional weights of 10-500 mg. Weights should be stored in a special box and must be
handled with forceps, NOT with the fingers to prevent soiling and erosion of the
weights. Apothecary weight sets are also available and are convenient to use when the
prescription is written in the Apothecary system.

INTRODUCTION TO LIQUID MEASUREMENT

The pharmacist is concerned with liquid measurement from two perspectives.
First, he/she should be concerned with the ability to accurately measure the components
of a prescription preparation. Secondly, he/she must be concerned with how the patient
will measure and deliver an accurate dose of a liquid medication.
The techniques used to measure liquids are probably the simplest of the operations
related to prescription compounding. At the same time, they are also the most
susceptible to errant selection and unprofessional execution leading to inaccuracies. In
this section, we will consider factors which influence selection of liquid measurement
devices.
Precision volumetric glassware is used to measure and/or deliver exact volumetric
quantities of liquid substances. The capacity of the vessel (1 ml, 50 ml, 1000 ml, etc.) is

8
inscribed on the vessel, and some types of devices will have calibration marks for
measuring multiple volumes. The inscriptions TD or TC mean, respectively, "to
delivery" and "to contain". A moment's reflection should indicate the significance of
these designations as they apply to the function of the glassware. Calibrated pipettes,
burettes, syringes and droppers are T.D. glassware; volumetric flasks and cylindrical or
conical graduates are T.C. glassware although in practice, graduates are used as T.D.
vessels for volumes of 1 ml or more.
Erlenmeyer flasks, beakers, and prescription bottles, regardless of markings, are
NOT volumetric glassware, but are simply containers for storing and mixing liquids.
The designated volume(s) express the approximate capacity of the vessel.
VOLUMETRIC GLASSWARE AND OTHER DEVICES INTENDED "TO
DELIVER"
Pipettes are recommended for the delivery of all volumes <5 ml and are required
for delivering volumes <1 ml (in the absence of an appropriate syringe). There are two
basic types of pipettes:

The single volume or transfer pipette is the most accurate and simplest to use
type, but is, obviously, limited to measurement of a fixed, single volume. Generally,
these pipettes deliver their inscribed volume by complete drainage of the pipette from
an etched mark. They are normally used for the accurate transfer of 1.0, 2.0, 5.0, 10.0,
and 25.0 ml of liquid.

The Mohr, or graduate multiple volume pipettes, is graduated from a point near
the tip to the nominal capacity of the pipette. Thus, it can deliver multiple volumes of
liquid with good volumetric precision. From a practical economic standpoint, the Mohr
pipette is generally the preferred instrument for compounding.

A pharmacist can accurately compound any prescription requiring relatively
small volumes of liquid if he/she has just three basic sizes of Class A Mohr pipettes
available:

1 ml Mohr pipette, subdivided in 1/100 ml
2 ml Mohr pipette, subdivided in 1/10 ml
5 ml Mohr pipette, subdivided in 1/10 ml

Hypodermic syringes come in a variety of sizes ranging from 0.5 ml (calibrated 0.01
increments) to 60 ml (calibrated in 2 ml increments). Syringes may be used to deliver a
wide range of liquid volumes with a high degree of accuracy. They are especially useful
for measuring and delivering viscous liquids.
The table below indicates that measurements made with syringes are more accurate and
precise than those made with graduated cylinders. Besides being easy to operate, these
syringes are unbreakable and economical. They are applicable in other experiments as
long as the reagents do not react with the chemicals used to manufacture the syringes.

9
Oral syringes are also available as a device for accurately providing a dose of liquid
medication to the patient. They are especially useful with children and elderly adults
who frequently require nonstandard doses, and for whom accuracy of dose is most
critical.

Graduates are used for measuring and transferring liquids in a manner that is less
precise than with a pipette. When appropriately used, graduates may be used to measure
and deliver volumes over 1 ml of most liquids with an acceptable level of accuracy. As
a general rule, a graduate should be used which has a capacity equal to or just exceeding
the volume to be measured (e.g. 50 ml of liquid should be measured in a 50 ml
graduate, not a 100 ml graduate). Graduates for pharmaceutical compounding may be
either conical or cylindrical, the latter being the more accurate and preferred device.
Studies have indicated that accuracy is improved when the lower portions of the
graduate are not used.

The following table gives the minimum volumes that should be measured for a given
potential error for a given cylinder size.

Most states specify the size and number of graduates, which must be on hand in a
registered pharmacy. As a rule, the required graduates will include all legal sizes up to

10
500 ml. In all instances, these will represent the minimum necessary equipment for
proper compounding.

Calibrated Medicine Droppers are often used to deliver small doses of liquid
medication, 1 ml or less, to the patient. Precision and accuracy of dose from droppers
can be very poor. Problems arise from the false assumption that a close relationship
exists between a drop and the volume of any liquid. The size of a drop of any liquid will
vary not only with differences in the construction and composition of the dropper, but
also with the viscosity, surface tension, and density of the liquid. Personal factors also
contribute to the problem. Two individuals dispensing the same liquid from identical
droppers may produce drops of different sizes because of variations in the pressure,
speed of dropping, and the angle at which the dropper is held.
In an effort so standardize the dropper, the United States Pharmacopoeia/National
Formulary (USP/NF) has recognized an official medicine dropper which is designed to
deliver 1 ml of water in 20 drops with an allowable 10% deviation (± 2 drops). This
stipulation does not appreciable improve the problem.
Some commercially produced medications are packaged with a marked dropper which
has been calibrated with that preparation.
In order to maximize accuracy of dosing of a compounded solution from a
medicine dropper, the pharmacist must calibrate the dropper with the intended
solution at the time of delivery.

VOLUMETRIC GLASSWARE INTENDED "TO CONTAIN"

Volumetric flasks are used to prepare solutions of a specific volume and concentration.
Because of their shape, the pharmacist would not reasonably expect them to deliver
their full volume.

Conical and Cylindrical Graduates are used to contain as well as to deliver specific
volumes of liquids.

NONVOLUMETRIC GLASSWARE AND DEVICES

Erlenmeyer flasks, beakers, and prescription bottles are not volumetric devices and
should NOT be used to measure liquids. "Graduation" marks on such vessels are only
approximations of liquid capacity. These devices should only be used to mix or store
solutions or other liquid preparations, unless you first calibrate them to a known
volume.

The Teaspoon and the problem concerning the actual volume of liquid contained in a
"teaspoonful" has existed for many years. Despite various recommendations, the
problem persists. Patients continue to self-administer liquid doses from spoons which,
in all probability, are far from standard.

11
The U.S. Pharmacopoeia/National Formulary (USP/NF) recognizes the problem and
provides the following statement: "Agreement has not been reached on a standard
official teaspoonful, in spite of the need for such a standard measure in connection with
compounding and labeling liquid medicines. For household purposes, the American
Standards Association has established an American Standard Teaspoon as containing
4.95 ± 0.24 ml. In view of the almost universal practice of employing teaspoons
ordinarily available in the household for the administration of medicine, the teaspoon
may be regarded as representing 5 ml." Household measures are, however, far from
standard. Teaspoons may be found with capacities ranging from 3 to 7 ml and the
volume of liquid which may be held in a given teaspoon varies with the viscosity and
surface tension of the liquid. Thus, the dosage becomes an almost unpredictable
variable. Errors in dosage can be minimized by:
Writing and formulating all prescriptions uses the metric system of measure.
Using the symbol for one fluid dram in the dosage instructions to represent one
teaspoonful.
Requesting physicians to designate on the prescription the number of ml or mg desired
in each dose.
Dispensing a standard calibrated teaspoon, oral syringe, or other calibrated measuring
device with each prescription for an oral liquid where such a dosage is used.

MEASUREMENT OF VISCOUS LIQUIDS

Sometimes you may need to measure viscous or oily liquids, which are difficult,
messy, or inconvenient to accurately, measure and deliver with volumetric devices. In
such cases, it is more reasonable to weigh the liquid than to measure it volumetrically.
The desired volume of the liquid can be converted to its equivalent weight if the density
or specific gravity of the liquid is known.

GUIDELINES FOR SELECTING LIQUID MEASUREMENT DEVICES

Always select the smallest device (graduate, pipette, syringe) that will
accommodate the desired volume of liquid. This will minimize the potential for errors
of measurement associated with misreading the scale.
Use a graduated pipette, syringe, or calibrated dropper to measure/deliver volumes <1
ml.
Remember that oily and viscous liquids will be difficult to remove from
graduates and pipettes, and at best require long drainage time. Consider using a
disposable syringe instead, or better yet, measuring by weight rather than volume.
Never use prescription bottles, nonvolumetric flasks, beakers, or household teaspoons
as measurement devices, unless you calibrate it yourself.
When small (<5 ml) or very accurate doses are required, provide the patient with a
calibrated dropper, oral syringe, or similar device to ensure proper dosing.

12
LIQUID MEASUREMENT TECHNIQUES

Pipettes
1. Single volume pipettes

Using a respirator (rubber bulb) for suction, draw the liquid into the pipet until it is
above the graduation. Caution: Since we may be using corrosive or poisonous liquids
mouth pipeting is strictly prohibited in the pharmaceutics lab.

Remove the pipette from the stock solution.
Wipe the end of the pipette with a tissue or Kim wipe.
While holding the pipette in a vertical position, release pressure, allow the liquid to
flow into a beaker (or other vessel) until the bottom of the meniscus coincides with the
etched line. Droplets, which remain suspended from the tip, can be removed by
touching the inside of the beaker with the tip of the pipette.
Allow the pipette to drain for 30 seconds (or up to 5 minutes for viscous liquids) while
touching the tip of the pipette to the inner side of the receiving vessel.

2. Mohr (graduated or calibrated) pipettes

The manipulations are essentially the same as with single volume pipettes except
that fractional volumes may be transferred by noting the meniscus level before and
after delivery. Thus, 1.50 ml may be delivered after observing an initial reading of 8.50
ml by allowing the liquid to flow until the meniscus reaches 7.00 ml. When working
with viscous materials, it is necessary to check the final reading after waiting
approximately 1 minute. (This can be very tricky!) It should be noted that the final
graduation of a Mohr pipette is usually some distance above the pipette tip so that
delivery is performed from graduation to graduation and not from graduation to tip as
with the single volume pipette. Make certain that you know which type of pipette you
are using to ensure accurate delivery.

MEASUREMENT TECHNIQUES WITH REGARD TO GRADUATES

Pharmaceutical graduates are available in both cylindrical and conical varieties.
Cylindrical graduates are generally considered to be more accurate than conical
graduates. The following steps will help to maximize accuracy when using cylindrical
or conical graduates.
Hold the selected graduate by the base with the left hand (for a right-handed person)
and elevated so that the desired mark is at eye level.
Hold the stock bottle with the right hand (label face up), and pour the liquid to be
measured into the center of the graduate, to avoid error resulting from the adherence of
material to the wall (especially with viscous liquids).

13
As the surface of the liquid approaches the desired mark, decrease the flow rate or use a
dropper or pipette to bring to final volume. The final volume should be determined by
aligning the bottom of the meniscus with the desired graduation mark. If the liquid is
densely colored or opaque, such as a suspension, the top of the meniscus should be
read.
Transfer the liquid from the graduate to the appropriate vessel or container,
allowing about 15 seconds for aqueous and hydro-alcoholic fluids to drain.
Approximately 60 seconds (or more) are required for more viscous liquids such as
syrups, glycerin, propylene glycol, and mineral oil to drain.
Errors in measuring may occur if the operator tilts the graduate or fails to read the
meniscus properly. Failure to perceive the true bottom of the meniscus is a common
source of error when measurement is taken against a light background. A more suitable
background consists of a broad black band on a white background.

Precautions

While graduates are volumetric devices, they should not be used for dissolving
solids in liquids. A solution should be prepared in a container such as a beaker or flask,
and returned to the graduate for adjustment of final volume.
Do NOT assume that the final volume of a prescription will be represented by the sum
of the individual volumes of ingredients. This is particularly important with the
admixture of aqueous and nonaqueous polar systems such as alcohol-water
combinations.

14
Experiment 1A

How to Use Class A Prescription Balance
LABORATORY PROCEDURE

 Arrest the balance by turning the arrest knob level the balance (Front
the back) by turning the leveling screw feet all the way into the balance
and then moving them the same direction until the 4 sites of the balance
are equidistant from the bench.

 Set the internal weights to zero. This is done by turning the calibrated
dial to zero.

 Place on weigh boat on each weighing pan. The small weigh boats will
hold up to 2 gms, while the larger weigh boats will hold up to 20rms.

 Unlock the balance by releasing the arrest knob and note the rest point
of the pointer on the index. If the pointer doesn’t rest at the center of the
index,. Then it will be necessary to level the balance left to right.

 Level the balance (left to right) by adjusting the leveling screw feet, to
shift the pointer left, grasp both the screw feet between the thumb and
four fingers and rotate so that thumbs move inward. To shift the pointer to
the right, rotate both screw beet so that fore fingers move toward back of
the balance, continue adjusting the screw feet slowly until the pointer
rests at the center of the index or swings equal distances to the right and
left at the center.

 Arrest the balance and place the required weight on the right pan. Place
the material to be weighed on the left pan.

 Release the balance and note the shift of the pointer on the index, if the
pointer shifts left, too much of the substance is on the pan and a portion
should be removed if it shifts rights there is too little of the substance and
more should be added, using spatula, remove or add material, arrest the
balance each time before a transfer is made.

15
Experiment 1B
I. Test of the Prescription Balance

Serial# ____________________
Model ____________________

A. SENSITIVITY REQUIREMENT - The balance should have a maximum
sensitivity of 6 mg with no load and with a load of 10 g on each pan. You don't have a 6
mg weight in your weight set, so you will use multiples of 10 mg weights in this test.

1. Level the balance and determine the rest point. Place a 10 mg weight on one of the
empty pans and again determine the rest point. How many divisions was the rest point
shifted by the 10 mg weight? ___________ Place a 20 mg weight on one of the empty
pans and again determine the rest point. How many divisions was the rest point shifted
by the 20 mg weight? __________ Place a 30 mg weight on one of the empty pans and
again determine the rest point. How many divisions was the rest point shifted by the 30
mg weight?_____

Plot "number of scale divisions shifted" versus "weight" for your three determinations.
Use Excel to make a trendline through the points and by calculation, determine the
weight that would cause a shift of one scale division.
2. Put a 10 g weight in the center of each pan. Determine the rest point.

16
3. Place a 10 mg weight on one of the pans having the 10 g weight and again determine
the rest point. How many divisions was the rest point shifted by the 10 mg weight?
_______ Place a 20 mg weight on one of the pans containing the 10 g weight and again
determine the rest point. How many divisions was the rest point shifted by the 20 mg
weight? __________ Place a 30 mg weight on one of the pans containing the 10 g
weight and again determine the rest point. How many divisions was the rest point
shifted by the 30 mg weight?_____
Plot "number of scale divisions shifted" versus "weight" for your three determinations.
Use Excel to make a trendline through the points and by calculation, determine the
weight that would cause a shift of one scale division.

4. The balance passes the sensitivity requirement if the balance is shifted one scale
division by 6 mg or less with no load and a load of 10 g. Does your balance pass this
test? __________

B. ARM RATIO TEST - This test is meant to check the equality of length of both
arms of the balance.

1. Determine the rest point of the balance with no weight on the balance pans.

2. Place 30 g of weights in the center of each pan and determine the rest point.

3. If the second rest point is not the same as the first, place a 20 mg weight on the
lighter side. The rest point should return to the original place on the scale or farther.

4. Does your balance pass this test? __________

C. SHIFT TEST - The shift tests are used to check the arm and lever components of
the balance.
1. Determine the rest point without any weights on the balance pans.

2. Place one of the 10 g weights in the center of the left pan and place the other 10 g
weight successively toward the right, left, front and back side of the right pan, noting
the rest point in each case. If in any case the rest point differs from the rest point
determined in (1), add a 10 mg weight to the lighter side and this should cause the rest
point to shift back to the rest point determined in (1) or farther.

3. Repeat (2) with the 10 g weight in the center of the right pan varying the position of
the weight on the left pan.

4. Make several observation in which both weights are simultaneously shifted to off-
center positions on their pans, i.e., both toward the inside, both toward the outside, one

17
front and the other back, etc. If in any case the rest point is shifted from (1), the addition
of a 10 mg weight should overcome the difference.

5. Does your balance pass this test? __________

D. RIDER AND GRADUATED BEAM TEST - This test detects improper
graduations or rider.

1. Determine the rest point for the balance with no weight on the pans.

2. Place a 500 mg weight on the left pan and move the dial or rider to the 500 mg point,
and determine the new rest point. If it is different from (1), add a 10 mg weight to the
lighter side. This should overcome the difference in rest points.

3. Repeat (2) with a 1 g weight on the left pan and the dial or rider on the 1 g point. If
the new rest point is different than (1), add a 10 mg weight to the lighter side. This
should overcome the difference in rest points.

4. Does your balance pass this test? __________

II. Weighing and Measuring
You should spend some time practicing your techniques with each apparatus. Use the
following prescription and compounding procedures as a guide to your practice. When
you feel comfortable with each technique, have the instructor or TA observe your
technique and then date and sign your skills check list.

18
Experiment 1C
Determination of Tablets Weight Variation:
Teaching Assistants will prepare Aspirin tablets in our pharmaceutical
Technology Laboratory. Although, the total weight of a tablet is determined by the
depth of the die cavity, bulk density of granules or powder, and uniformity of
particulate flow; tablet weight variations must fall within certain specifications
established by the USP.
Procedure:
1. Students should divide themselves into group of two.
2. Each group should select 10 tablets
3. Weigh accurately the 10 tablets individually and listed in Table 1.
4. Use excel program to calculate the calculate the average weight and
the relative standard deviation (RSD).

Tablet Weight of Tablet % Labeled
# (mg) Claim
1
2
3
4
5
6
7
8
9
10

Note: Labeled claim is 400 mg
 Mean (as % of labeled claim) _________
 Standard Deviation __________
 RSD __________

19
Experiment 2
Aliquot and Geometric Dilution methods:

Example

Rx
 Bentonite 15mg
 Talc ad 200mg

1. Determine factor for the aliquot method
Factor = F = 120 / 15 = 8

2.Multiply all the ingredients by this factor

Rx
 Bentonite 15x8 = 120mg
 Talc ad 200x8 = 1600mg
i.e. talc = 1600-120 = 1480mg

3. Preparation

Due to the presence of talc in large proportion than Bentonite we have to use the
geometric dilution method to produce homogeneous mixture.

Use of the geometric dilution method

Talc (mg) Mixture (mg)

1. 120 mg Bentonite + 120 = 240

2. 240 Mix. + 240 = 480

3. 480 Mix. + 480 = 960

4. 960 Mix. + 620 = 1480

20
Rx
 Charcoal 15 mg.
 Talc. Ad. 200 mg.

Factor : [120/ 15] =8 fold

Amount of Charcoal = 15 x 8 =120 mg.
Total amount 200 x 8 = 1600 mg.
i.e. Amount of Talc =1600-120 = 1480 mg.

Use of the geometric dilution method

Talc (mg) Mixture(mg)
1. 120 mg Charcoal + 120 = 240

2. 240 Mix. + 240 = 480

3. 480 Mix. + 480 = 960

4. 960 Mix. + 640 = 1480

product
with homogenous mixture.

21
PART 2

CONCENTRATION AND DILUTION

22
INTRODUCTION
MilliEquivalents:

Equivalent weight is molecular weight divided by the valence of the molecule.
Milliequivalent is one thousandth of the Equivalent. For Examples;

A prescription calls for 25 milliequivalents of sodium chloride. What quantity, in
mg, would be required? 1 equivalent NaCl = 58.5 gm, 1 milliequivalent = 58.5 mg;
25 mEq x 58.5 mg/mEq = 1.463 g

A pharmacist receives an order for 10 mEq of Ca+. How much of a standard 10%
CaCl2 solution should be used for this order?
Ca = 40/2 = 20 mg/mEq

1/10 mEq = 20 mg/ x , then x = 200 mg Ca required
CaCl2 = 40 + 71 = 111
40/111 =200/ x mg , x = 555 mg CaCl2 required
10 /100ml = 0.555 g / x , x = 5.55 mL of the 10% CaCl2 solution

Moles and Millimoles:

Moles are weight of solute in gm/formula weight [i.e (w2/M2 ). Millimoles are one
thousandth of the moles [[(w2/1000*M2 )]. Where, w2= wt. of solute and M2 =
molecular weight of solute. For Example;

How many millimoles of NaCl are contained in 1 liter of 0.9% Sodium Chloride
Solution? (Formula weights: Na=23, Cl=35.5, NaCl=58.5).
0.009 x 1000 mL = 9 g NaCl
1 mole NaCl weighs 58.5 g
1/58.5g = x /9g , x = 0.154 mole = 154 millimoles

Osmolality:

Osmolality = number of moles * number of ions
Milliosmoles = [ # of moles /(1000* # of ions)], For Example;

What is the osmolality (number of milliosmoles) of 1 liter of 0.9% sodium chloride
solution? (Assume complete dissociation)
Na=23, Cl=35.5, NaCl=58.5, NaCl --> Na+ + Cl

# millimoles NaCl present per liter = 154 from previous problem
154 millimoles NaCl x 2 species (Na + Cl) = 308 mOsmol/liter

23
What is the osmolality of 10% CaCl2 solution? (Assume complete dissociation)
(Formula weights: Ca=40, Cl=35.5, CaCl2=111g/L)
10% CaCl2 = 100 g/1000 mL

100 / 111 g = x / 1 mole

Then, x = 0.9 moles/liter = 900 millimoles
CaCl2 ----> Ca++ + 2 Cl = 3 species
900 millimoles CaCl2/L x 3 species = 2700 mOsmol/Liter

Molarity and Molality:

Molality is the number of moles per liter while molality is number of moles per
kilogram. Therefore,

Molarity = [# of moles / Liter]

Moles = wt. of solutes (w2)
M2
Where; wt.=weight, w2= wt. of solute and M2 = molecular weight of solute.
Therefore,

Molarity = [(w2/M2 )/ (V1/1000)] = [(w2 )* 1000/ (M2 )*(V1)]
And
Molality = [(w2 / M2 )/ (w1/1000)] = [(w2 )* 1000/ (M2 )*(w1)]
Where; w1= wt. of solvent.

Dilution From Stock Solution

The best method is to use the following Eq.

C ı Vı = C2 V2
Cı = Conc. of desired preparation
Vı = volume desire preparation
C2 = conc. of S.S.
V2 =volume of S.S. contains desired quality V2=?

You are provided with 5% aqueous of a drug solution. please calculate the volume
of the stock solution needed to prepare 50mls of 0.2%aqueous solution.

Ans.
0.002 x 50 = 0.05 x V2
Then, V2 = 2mls

24
Experiment 3
Preparation of Solution with given Concentration:

 Prepare 50 ml. of 0.05M of drug A (M wt.= 500 mg.)

Calculations:

molarity = [# of moles / Liter]

Moles = wt. of solutes (w2)
M2

Where; wt.=weight, w2= wt. of solute and M2 = molecular weight of solute.
Therefore,

Molarity = [(w2/M2 )/ (V1/1000)] = [(w2 )* 1000/ (M2 )*(V1)]

Since V1=50, then

M=0.05=[(w2 )* 1000/ (500 )*(50)] Therefore

w2=[0.05 *500 * 50 ]/1000 =0.125 g = 125 mg

 Calculated Prescription:

Rx
Drug A 125 mg.
H2O ad. 50 ml.

AUST Date
0.05 ml. of drug A
sig.

 Prepare 0.2 M of KCl (M2 =79.5g/ml)

Calculation :

M = (W2 x 1000) / (M2 x V1)

25
0.2 = (W2 x 1000) / (74.5 x 50 )

W2 = 0.745gms

Preparation:

1. Wt 0.745g of KCl and place it in a bottle.
2. Add 50ml of water
3. Write label.

AUST Date

0.2 M of 0.2 M of KCl
Sig .

 Prepare 50 mls of KCl containing 10mEq.

Calculation :

Step1: Calculate the quantity of KCl (in g.) that is present in 1mEq.

Eq = _[Mwt./ Valency] = [74.5/ 1] = 74.5g.

mEq = [_74.5g / 1000 ]_ = 0.0745g.

Step 2 : Calculation of the desired quantity . (Proportionality method).

1mEq_ = _0.0745g_
10mEq Q(g)

Q(g) of Kcl = 10 x 0.0745 = 0.745g.

Calculated Preparation:

Rx
 Kcl 0.745
 Water ad 50mls.

26
Procedure:

1.Wt. 0.745g of Kcl and place it in a bottle .
2.Add 50ml of water and shake.
3.Write label.

AUST Date
10mEq of Kcl
sig.

27
Experiment 4
Dilution of stock solutions :-

1. You are provided with 5% aqueous Iodine solution B.P. please prepare
50mls of 0.2%aqueous iodine solution.

Calculation :-

First method:

 Calculate amount of Iodine required for preparing the desired solution.

Original s.s. 0.2 gms 100 mls
Desire ? 50 mLs

Q(g) = [50 x 0.2 / 100 ] = 0.1g

 Calculate the volume of stock solution that contain the quality.

Original S.S 5gms 100mls
Desire 0.1gm ?

Q(ml)of S.S.= (0.1 x 100)/5 = 2mls

Preparation :

Take 2mls of S.S and complete it to 50ml.

Second method :

C ı Vı = C2 V2
Cı = Conc. of desired preparation
Vı = volume desire preparation
C2 = conc. of S.S.
V2 =volume of S.S. contains desired quality V2=?

0.002 x 50 = 0.05 x V2
V2 = 2mls

28
Preparation :

1. Take 2mls of S.S and place it in a dispensing bottle and ad 48ml of distilled water.

2. write label

AUST DATE

0.1% KMno4
sign.

2. You are provided with 0.1% potassium permanganate ( KMno4) please
prepare 50mls,0.02% soln.

V1 C1 = V2 C2
50 x 0.0002 = V2 X 0.001
( 50 X 0.0002) /0.001 = 10mls

preparation :

1. Take 10mls of KMno4 S.S and complete it to 50ml

2. Write label.

AUST Date
0.1% KMNo4
Sig.

29
PART 3

PHARMACEUTICAL SOLUTION

30
INTRODUCTION

The study of pharmaceutical solutions is essential to the practicing pharmacist
and can be, at times, somewhat complex. In addition to considering the therapeutic
appropriateness of the drug, the pharmacist must consider many factors regarding the
chemical and physical aspects of the product. Is the drug soluble in an acceptable
solvent? Is it chemically stable in solution and for how long? Are two or more solutes
chemically and physically compatible in solution? How will changes in temperature, pH
or light exposure affect the product? Should the product be preserved, buffered, or
flavored and how? How should the product be packaged and stored?
You may be wondering if you really need to know all of these things when so many
products are commercially available. Absolutely! Many oral solutions are not produced
commercially because they are unstable and have a short shelf-life or are used in such a
small patient population that they are unprofitable to produce commercially. Hence, you
may be called upon to formulate and dispense many such products.

As with any product, safety and accuracy of dosing are our ultimate goals. Thus,
you must learn to read and interpret the prescription properly, to make the necessary
calculations to prepare a product of desired strength, and to use the proper judgments
and formulation techniques to ensure a stable, potent product. Finally, you must learn to
clearly and accurately label the products with the appropriate instructions for use. There
may be times when written or verbal instructions are necessary to supplement the label
directions.

A solution is a thermodynamically stable, one-phase system composed of 2 or
more components, one of which is completely dissolved in the other. The solution is
homogeneous because the solute, or dispersed phase, is dispersed throughout the
solvent in molecular or ionic sized particles. Broadly defined, a solution may be any
combination of solids, liquids, and/or gases. We will restrict our definition of
pharmaceutical solutions to those composed of a solid, liquid, or gas dissolved in a
liquid solvent.

The assignment of the terms solute and solvent is sometimes arbitrary.
Generally, the solute is the component present in the smallest amount and the solvent is
the larger, liquid component. Water is nearly always considered the solvent.
Pharmaceutical solutes may include active drug components, flavoring or coloring
agents, preservatives, and stabilizers or buffering salts. Water is the most common
solvent for pharmaceutical solutions, but ethanol, glycerin, propylene glycol, isopropyl
alcohol or other liquids may be used, depending on the product requirements. To be an
appropriate solvent, the liquid must completely dissolve the drug and other solid
ingredients at the desired concentration, be nontoxic and safe for ingestion or topical
application, and be aesthetically acceptable to the patient in terms of appearance, aroma,
texture, and/or taste.

31
The solubility of a drug is the expression of the quantity of a drug that can be
maintained in solution in a given solvent at a given temperature and pressure. It is
usually expressed as the number of milliliters of solvent required to dissolve 1 gram of
the drug. Understanding drug solubility is critical in formulating solutions. This topic
will be covered in more depth in a later exercise.

A saturated solution is one that contains the maximum amount of solute that the
solvent will accommodate at room temperature and pressure. A supersaturated
solution is one that contains a larger amount of solute than the solvent can normally
accommodate at that temperature and pressure. It is usually obtained by preparing a
saturated solution at a higher temperature, filtering out excess solute and reducing the
temperature. Saturated and supersaturated solutions are physically unstable and tend to
precipitate the excess solute under less than perfect conditions (e.g. when refrigerated or
upon the addition of other additives).

A differentiation is sometimes made between solutions on the basis of solute
molecular size. Micromolecular solutions consist of dispersed molecules or ions in the
1-10 A size (MW < 10,000). In macromolecular solutions (MW > 10,0000), the
solutes are in true solutions, but the solute size of macromolecular solutions lends
special properties to them. Because the particles are so large, most cannot be sterilized
by filtration. The solutions are also quite viscous, and may be used as thickening agent
for other dispersed dosage forms. Macromolecular solutions include those containing
acacia, methylcellulose and other cellulose derivatives, and proteins such as albumin.

CLASSIFICATION OF SOLUTIONS BY SOLVENT TYPE:

1. Aqueous solutions are the most prevalent of the oral solutions. Drugs are dissolved
in water along with any necessary flavorings, preservatives, or buffering salts. Distilled
or purified water should always be used when preparing pharmaceutical solutions.
The following are examples of aqueous pharmaceutical solutions.

2. Syrups are concentrated, viscous, sweetened, aqueous solutions that contain less than
10% alcohol , e.g. Syrup USP, Wild Cherry Syrup USP.

3. Aromatic waters are saturated solutions of volatile oils in water and are used to
provide a pleasant flavor or aroma, e.g. Peppermint Water, USP.

4. Mucilages are thick, viscous macromolecular solutions produced by dispersing
vegetable gums in water. They are commonly used as suspending or thickening agents,
e.g. Acacia Mucilage; Tragacanth Mucilage.

5. Aqueous acids are dilute aqueous solutions of acids (usually < 10%), e.g. Diluted
HCl, USP.

32
PHARMACEUTICAL APPLICATION OF SOLUTIONS

Solutions have a wide variety of uses in the pharmaceutical industry. They are
therapeutically as vehicles for oral, parenteral, topical, otic, ophthalmic, and nasal
products. They are also used as flavorings, buffers, preservatives, and suspending
agents for a variety of liquid dosage forms. Concentrated stock solutions often serve as
components of extemporaneously prepared products. Test solutions also play an
important role in the analysis of pharmaceutical products of all types.

33
Experiment 5

A. Aqueous Solution

1. Aromatic Water

 Preparation of Double Strength Chloroform Water (B.P)

Rx
Chloroform 5 ml.
Water ad. 1000ml.
Send 100ml.

Calculate 5ml. 1000ml.
V2=?? 100 ml.

Vol. of CHCL3 =[100x5/1000] = 0.5 ml.

Rx
Chloroform 0.5 ml.
Water ad. 100 ml.

Used as:
1.vehicle.
2.flavouring agent
3.preservative.

AUST Date
Double strength chloroform water.
Sig.

34
 Preparation of Strong Sodium Salicylate Mixture (B.P.C)

Rx
 Sodium Salicylate 10mg.
 Sodium metabisulfide 1 mg.
 Double strength chloroform water 525
 Water ad. 1000ml.
 Send . 50 ml.

Calculation:
a) Sod. Salicylate
s.s prep.
10g. 1000ml.
?? 50 ml.
amount of sod. Salicylate = 50x10 =0.5 g.
1000
b) sod. metabisulfide.

original 1g. 1000ml.
prepared ?? 50ml.

1x50 = 0.05g.
1000
c) D.S.C.W.

original 525ml. 1000mls.
prepared ?? 50 mls.

mls. Of D.S.C.W. 50X525 = 26.5 mls.
1000

Calculated Preparation:

Rx
Sod. Salicylate 0.5g.
Sod. Metabisulfide 0.05g.
D.S.C.W. 26.15mls.
Water ad. 50mls.

(120mg. Is the least wt. for the balance)
so we use aliquot method

35
0.05x4=0.2 g. and dissolve it in 4 mls.
0.2 4
1.05 ??
(4x0.05)/0.2 =1 ml.

Procedure:

 Prepare 50 ml. of D.S.C.W. (dissolve 0.25 ml. of CHCL3 /50 mls.)
 Take 26.15 mls .of D.S.C.W. only.
 Weigh 0.5 g. of sod. Salicylate and dissolve it in 26.25 ml. of D.S.C.W.
 Dissolve 0.2 g. of sod. metabisulfide in 4 mls. of water.
 Take 1 ml. of sod. metabisulfide solution and put it in D.S.C.W. solution.
 Transfer into 50 ml. measuring cylinder and adjust the volume. to 50 ml. with
water.

AUST Date
Aromatic water
Sig.

 Preparation of Peppermint Water B.P.

 Peppermint oil 2ml.
 Talc 15 g
 Purified water ad. 1000 ml.
 Send 50 ml.

Calculation:

Peppermint oil reducing factor = 50 /1000 = 0.05

Original 2ml. 1000ml.
?? 50 ml.
Q. of oil =2 x (50/1000) =2 x 0.05 = 0.1ml.

Talc

36
Q. of talc . 15x0.05 =0.75 g.

Calculated Preparation:

Rx
Peppermint oil 0.1 ml.
Talc 0.75g.
Water ad. 50ml.

Procedure:

 Wt. 0.75g. of Talc and put it in dry motor.
 Add 0.1ml. of oil to the powder and triturate.
 Add 30 ml. of water and triturate .
 Filter using Buckner funnel and transfer to measuring cylinder and complete the
vol. to 50 ml.
 Write label.

AUST Date
Peppermint water B.P.
Sig.

37
Experiment 6
2. Solution for Internal use :

 Preparation of Potassium Iodide Expectorant preparation:

Rx
 Potassium Iodide(KI) 25g (Expectorant, complex with I2 and
Increase solubility of Iodine.)
 Iodine 12.5g ( Expectorant and important for thyroid
gland)
 Alcohol 90% 40ml Solvent for Rose oil.
 Water 250ml Solvent I2 and KI.
 Rose oil 4 ml Flavoring agent.
 Glycerol ad. 1000 Vehicle, Humectant and emollient.
 Send 50 ml.

Calculation: F= (50/1000)=0.05

Calculated Preparation
Rx
KI 1.25g.
 I2 0.625g.
Alcohol 2ml.
Water 12.5ml.
Rose oil 0.2ml.
Glycerol ad. 50ml.

Procedure:

1. Dissolve 1.25g of KI and 0.625g of I2 in 12.5ml of water (gradually).
2. In test tube dissolve 0.2 ml Rose oil in 2ml alcohol (if not dissolved completely
add some glycerol).
3. Add alcoholic solution (step2)into aq. Solution.
4. Transfer solution into measuring cylinder and ad glycerol up to 50ml.
5. Write label.

AUST Date
KI expectorant preparation.
Use as directed.
Sig.

38
3. Solution for External use :

 Preparation of Aqueous Iodine Solution B.P

Rx
 Iodine 50g.
 KI 100g.
 Water ad. 1000ml.
 Send 50 ml

Calculation:

Factor = ( 50/1000) =0.05
I2 +KI K(I-----I-I) (poly Iodide complex)

Rx
 Iodine 50x0.05 = 0.5 g.
 KI 100x0.0 = 5 g.
 Water 1000x0.05 = 50 g.

Procedure:

1. Wt. 2.5 g. of I2 and 5.0 g of KI and place it in a dispensing bottle.
2. Add some of water and shake well.
3. Write label.

AUST Date
Aqueous Iodine solution B.P.

Sig.

External use only

39
Experiment 7

4. Viscous Aqueous Solution ( Syrups ) :

 Preparation of Syrup B.P

Rx
Sucrose 667g
Purified Water Q.S 1000g

Sent 300ml

Procedure:
Dissolve the Sucrose in Purified Water in beaker by careful heating on
Water path. Stir frequently until dissolved & adjust volume. Cool it and
filter through gawz.

Note: it is preferred to add 10% Glycerol to act as preservative & to prevent
crystallization.

 Preparation of Acacia Syrup USP

Rx
Acacia 1g
Sod. Benzoate 0.01g
Vanilla Tincture 0.05ml
Sucrose 8g
Purified Water Q.S 100ml

Procedure:
1. Mix Acacia, Sod. Benzoate & Sucrose.
2. Add small portion of Purified Water and mix well.
3. Heat the mixture on a water path until solution is completed.
4. When cool, add the Vanilla Tincture & complete with water to 100ml

40
Experiment 8

 Preparation of Cough Syrup :

Rx
 Diphenyl hydramine Hcl gr.v V 5*0.065=0.325g
 Ammonium chloride gr VL 45*0.065=2.925g
 Sod. Citrate gr XX 0.065*20=1.300g
 Aqueous (H2O) flz ii 4*2=8ml
 Flavor & Colour Q.S.
 Syrup Q.S.

Procedure:
 Dissolve in 8ml of H2O (in a beaker)
 Transfer the solution to a measure cylinder(100ml).
 Complete with syrup to 100ml.
 Transfer the preparation to glass bottle, add flavor & colour (1 drop of rose
oil & 2drops of colour)

Role of each Ingredient

Diphenyl hydramine Hcl : Antihistamine
Ammonium chloride : Expectorant
Sod. Citrate : Expectorant
Syrup : Vehicle, solvent & Sweeting agent
Water : Solvent

41
 Preparation of Cough Syrup for diabetic:

Rx
 Diphenyl hydramine Hcl gr.v V 0.325G
 Ammonium chloride gr VL 2.9859
 Sod. Citrate gr XX 1.3g
 Aqueous (H2O) flz ii 4*2=8ml
 Saccharine Sod. 0.084g
 Methyl cellulose (0.5%w/v) Q.S.
 Flavor & Colour Q.S.
Sig: one table spoon to be taken

Procedure:
As in cough syrup (except the prepared of Methyl cellulose (0.5%w/v)

N:B prepared of Methyl cellulose (0.5%w/v)

42
Experiment 9

B. Non-Aqueous Solution

INTRODUCTION

Although from their physical properties many solvents appear to be desirable for
use in pharmaceutical products, the physiological actions of the solvents greatly limit
their use. With few exceptions, most organic solvents are irritating or toxic.
Aromatic hydrocarbons cause paralysis of the central nervous system and are irritating
to the skin; methyl alcohol is toxic, and butyl and amyl alcohol are irritating; volatile
ethers paralyze the central nervous system, and are irritating to mucous membrane
increases; ketones are mildly irritating; and the low molecular weight esters are
irritating. Thus, toxicity and irritation limit the solvents employed to a few compounds
such as glycerin, alcohol, and propylene glycol for internal use. For external use
saturated aliphatic hydrocarbons, ether, and glyceryl esters of aliphatic acids may be
added to the list of acceptable pharmaceutical solvents.

Propylene glycol has been employed as a solvent for oral and parental solutions
of drugs such as antihistamines, barbiturates and vitamins. Although orally
administered propylene glycol has a low toxicity in animals, it may exhibit a weak
central nervous system depressant activity and an antagonistic action against
pentylenetetrazol. Thus, the use of propylene glycol as a physiologically inert solvent is
not recommended. Infants with rickets have become stuporous for hours after treatment
with 600,000 units of vitamin D administered in 60 ml of propylene glycol as single or
divided doses in a 24-hour period.

Nonaqueous solutions are those solutions which contain solvents other than
water, either alone or in addition to water. Alcohol or a binary mixture containing
alcohol is the most commonly used nonaqueous solvent. In addition to the
pharmaceutical classes of elixirs, spirits, tinctures, and fluid-extracts, individual
products such as Chloroform Liniment and Coal Tar Solution are alcoholic solutions.

Elixirs

Elixirs are defined by the USP as "clear, sweetened, hydroalcoholic liquids
intended for oral use." Their alcohol content ranges from 5-40% (10-80 proof), e.g.
Phenobarbital Elixir, USP. Elixirs are flavored hydroalcoholic solutions to which
glycerin often is added to enhance the solvent properties and act as a preservative. The
alcoholic contents of elixirs varies widely; actually a few commercial elixirs contain no
alcohol, while other elixirs may contain as much as 40% alcohol. The concentration of
alcohol is determined by the amount required to maintain the drug or volatile oil in

43
solution. The addition of aqueous solutions to elixirs may cause turbidity or separation
by lessening the alcohol concentration.

Spirits

Spirits or essences are alcoholic or hydroalcoholic solutions of volatile
substances (usually volatile oils) with alcohol contents ranging from 62-85% (124-170
proof). They are most frequently used as flavoring agents, e.g. Peppermint Spirit USP.
Some spirits are used for their medicinal effect, but most spirits are a convenient means
of obtaining a proper amount of flavoring oil. All essences have a high alcohol content,
and the addition of water invariably causes turbidity and separation.
Whisky and Brandy are prepared by distillation. Compound Orange Spirit, Camphor
Spirit, and Compound Cardamon Spirit are prepared by simple solution.

Tinctures

Tinctures are alcoholic or hydroalcoholic solutions prepared from vegetable or
chemical substances. The concentration of solute varies up to 50%, e.g. Vanilla
Tincture USP, Iodine Tincture USP. Tinctures are alcoholic solutions of nonvolatile
substances, which are generally extracted by maceration or percolation. Tinctures of
potent drugs represent the activity of 10 g of the drug in each 100-ml of the tincture;
they are 10% tinctures. With a few exceptions, nonpotent tinctures represent 20 g of the
drug per 100 ml of tincture.

Tinctures are prepared chiefly by percolation and maceration. Percolation is the
procedure of choice when the crude drugs are cellular in structure; plant exudates tend
to become impacted in the percolator and stop the flow so that maceration is preferred
in such preparations. Moderately coarse powders are preferred, because coarse powders
are slowly penetrated by the menstruum and fine powders tend to clog the percolator.
Usually alcohol or a hydroalcoholic menstruum is employed. The choice of menstruum
depends on the solubility, stability, and ease of removal of the desired constituent.
Other inactive constituents are extracted, but if the material is not objectionable, it is
allowed to remain.

In the process of percolation, the drug is dampened with the menstruum and
allowed to stand for a short period before packing the percolator so that the drug may
expand as the menstruum is absorbed. If the drug is packed into the percolator and
moistened, the swelling would pack the drug so firmly that the percolate could not flow.
The menstruum is then added to cover the drug and the lower opening is closed when
the liquid is about to drip from the percolator. This permits the air between the particles
to escape as the menstruum descends. Maceration for a prescribed time permits
saturation of the menstruum in contact with the drug, assuring a more nearly complete
extraction.

44
The menstruum is then allowed to flow or percolate at a definite rate. Normally
the percolate collected is assayed before final volume is reached, and then it is adjusted
to the proper strength.

In the process of maceration the drug is soaked with the menstruum in a closed
container. The closed container prevents the loss of volatile constituents and
evaporation of the menstruum. The mixture is agitated frequently so the menstruum at
the bottom of the container does not become saturated and incapable of extracting
further drug. Circulatory maceration is an efficient modification which eliminates the
need for agitation. When heat is employed in maceration, the process is known as
digestion. The mixture is then transferred to a filter, and the residue is washed with
sufficient menstruum to bring the tincture to final volume.

Preservation

Examination of unofficial liquid pharmaceutical specialty products and similar
official products indicates that a minimum of 15% alcohol is required to preserve the
product from microbial growth if no other preservative agents are present. Industrial
pharmacists usually regard 15% alcohol as adequate for the preservation of products
with a pH of 5, while 18% has been considered adequate for neutral or slightly alkaline
preparations. It is obvious that products such as tinctures, spirits, and fluid extracts
possess alcohol in concentrations that far exceed these values and need no further
preservative.