ROUTES OF DRUG ADMINISTRATION By Zubair Latif Pharmacology and Toxicology UVAS, Lahore Drug Absorption Absorption is the process by which a drug enters the bloodstream without being chemically altered or The movement of a drug from its site of application into the blood or lymphatic system Factors affecting route of drug administration Physicochemical properties of the drug Onset of action required Type of response required Site of desired action Nature and Formulation of drug Circulation at the site of absorption Biotransformation Condition of patient Routes of Drug Administration The possible routes for drug entry into the body may be divided into two classes: ENTERAL PARENTERAL ENTERAL ROUTES ENTERAL Drug placed directly in the GI tract: Oral swallowing (p.o., per os) Sublingual placed under the tongue Rectum Absorption through the rectum Oral Administration of drug by ingestion. Not very much preferred in animals because of restraining of animals is difficult. Given in the form of drench or mixed with feed or water. Applied with the help of stomach tube, or Nasogastric tube. If rapid effect is required drug may be administered before meal if drug causes irritation may be administered after meal. Advantages of oral route Can be self- administered, pain free, easy to take. Absorption takes place along the whole length of the GI tract. The drugs preparations needs no sterilization. Both solid and liquid dosage forms can be given through this route. Most suitable route for GIT Infections and GI parasites Cheap as compared to most other parenteral routes. Disadvantages of oral route Drug action has slower onset son not suitable in case of emergency. Drug absorption is irregular and unpredictable due to presence of ingesta. First-pass effect - drugs absorbed orally are initially transported to the liver via the portal vein. Irritation to gastric mucosa - nausea and vomiting. First-pass Effect The first-pass effect is the term used for the hepatic metabolism of a pharmacological agent when it is absorbed from the gut and delivered to the liver via the portal circulation. The greater the first-pass effect, the less the agent will reach the systemic circulation when the agent is administered orally Disadvantages of oral route Destruction of drugs by gastric acid and digestive juices. Unpleasant taste of some drugs. Unable to use in unconscious patient. Poor administration techniques may lead to intratracheal delivery and subsequent aspiratory bronchopneumonia Sublingual/Buccal Drugs are taken as solutions or smaller tablets which are held in the mouth or under the tongue. Advantages Rapid absorption Drug stability Avoid first-pass effect Disadvantages Inconvenient Small doses Unpleasant taste of drugs Rectal route of drug administration 1. Unconscious patients and children. 2. If patient is nauseous or vomiting. 3. Easy to terminate exposure. 4. Absorption may be variable. 5. Good for drugs affecting the bowel such as laxatives. Parenteral Intravascular Intravenous Intra-arterial Extravascular Other Extravascular Intramuscular Inhalation Subcutaneous Topical Application Intra-articular Other Mucous Membranes Intraperitoneal (Vagina, Nose…) Intracardial Intrapleural Epidural Intradermal Intrathecal Intraoosseous Intravascular Intravenous Intra-arterial Absorption phase is bypassed (100% bioavailability) 1.Precise, accurate and almost immediate onset of action, 2. Large quantities can be given, fairly pain free 3. Greater risk of adverse effects a. high concentration attained rapidly b. risk of embolism Intravenous route of drug administration Drug solution is injected directly in one of superficial vein either as bolus or infusion. In cattle and Horses vein is jugular, In sheep and goat jugular, Caphaneous and cephalic, vein is and in dog vein is Caphaneous and cephalic. Identify the vein to be used in some animals this is straightforward, others may have to palpate (feel for) veins. Always inject with the blood flow. Clean the site with soap and water, or an alcohol swab. Introduce the needle into the vein at a shallow angle. Intravenous route of administration Pull back the plunger to identify that the needle is in a vein a small amount of dark red venous blood should trickle into the syringe. Inject slowly to reduce the likelihood of damage to the vein and to lower the overdose risk. Remove the needle slowly if the needle is removed too quickly, the vein may collapse. Immediately apply pressure to the site bruising is caused by bleeding into the surrounding tissues. Immediate firm pressure will limit the amount of bruising caused. Advantages of Intravenous route Quick onset of action. This route is used when precise control of the drug effect is required. Highly irritating and non isotonic solutions can be given by slow IV because dilution provided by circulating blood. Large volume of fluids can be administered through this route. Disadvantages of Intravenous route This route required special technique. Air embolism may put life of animal in danger. Extra vascular accumulation of irritant drugs may cause necrosis of peripheral tissues and phlebitis. Not suitable for insoluble drugs like oils and suspensions. Intramuscular route of administration Drug is injected deep between the layers of one of large skeletal muscle because these are richly supplied with blood and less with nerves. This route is used for providing systemic effects of drugs. Advantages of Intramuscular route Route of choice in animals. Very rapid absorption of drugs in aqueous solution and oleaginous suspensions. Absorption of drug is rapid except for oily and depot preparations. The duration of action is longer than for IV injection, but usually a little shorter than for subcutaneous administration. Mostly suitable route for fractious, wild and zoo animals, which may be difficult to restraint. Disadvantages of Intramuscular route Large volume of fluids cannot be injected. There is possibility of improper deposition of drug in nerve, blood vessels, fat or connective tissues. It is not suitable for emergency situations because conditions like cardiovascular collapse or shock may impede absorption of drugs. Subcutaneous route of administration The drug preparation is deposited in the loose subcutaneous tissue (Under skin).It is richly supplied with nerve but less blood supply. Advantages Large volume of non irritating drugs may be administered. Absorption of drugs is slower than IM and IV. It is suitable for depot preparations. Disadvantages Not suitable for irritant drugs Intradermal route of administration The drug preparation is injected in the dermis of skin. Injection is applied on the skin of most sensitive part of body. Advantages Used for diagnostic purposes, like tuberculin test, Malein test, Antibiotic sensitivity test. Disadvantage Painful condition. Intra articular Injection Inject the drug in Joints For the treatment of arthritis More skill is required Painful application Damage the cartilage Intraperitoneal drug administration Injection into Peritoneum (body cavity). IP injection is more often applied to animals than humans. It is generally preferred when large amounts of blood replacement fluids are needed, or when low blood pressure or other problems prevent the use of a suitable blood vessel for Intravenous Injection. Advantages Rapid absorption Large volume of drug may be injected. Used frequently in lab animals. Disadvantages Not suitable for irritating compounds because it causes chemical peritonitis. There is possibility of puncturing of intestine or other abdominal organs. Intra Cardiac Injection Drug is injected directly in to the heart Epidural Injection An injection in the epidural space. It is a space located in the spine between the vertebrae and the dural sac, which surrounds the spinal cord. Intrathecal Injection Drugs which cannot cross BBB are administered through this route Intraoosseous Injection Injection in Bone marrow Other Extravascular Inhalation 1.Gaseous and volatile agents and aerosols 2.Rapid onset of action due to rapid access to circulation a. Large surface area b. Thin membranes separates alveoli from circulation c. High blood flow Topical route of drug administration SKIN Absorption is directly proportional to the lipid solubility of drugs. Absorption through skin can be enhanced by use of dressing, inunctions or special drug delivery devices like ear tags and transdermal patches. BATH It is immersion of the body in medicated water. Baths are given generally for their local effects upon the skin in cutaneous disorders. DIPS It is type of bath in which body is dipped in medicated fluid for a certain time. In vet. Dips are used in small animals to kill ectoparasites. Topical route of drug administration INUNCTIONS It is the application of semisolid or liquid drug on the body by rubbing. DUSTING It is application of fine particles of solid on surface of body. APPLICATION ON MUCOUS MEMBRANES Intramammary Administration. Intra ocular Administration. Intra aural Administration. Intranasal Route. Intravaginal Intrauterine Intra Prepucial Specialized drug delivery systems Transdermal Drug delivery system Transdermal drug delivery system are topically administered medicaments in the form of patches that deliver drugs for systemic effects at a predetermined and controlled rate. Specialized drug delivery systems Liposomes. Liposomes are minute vesicles of lipid bilayers enclosing and aqueous compartment. They are utilized for the transportation of drugs to areas not normally accessible to free form of drug. Specialized drug delivery systems Dermojet/Hypospray It is a special form of subcutaneous administration in which needle is not used. A high velocity jet of drug solution is projected from a micro fine orifice using a gun like device. It is painless method for insertion of drug in the body. Route for administration -Time until effect- Intravenous 30-60 seconds Intraosseous 30-60 seconds Inhalation 2-3 minutes Sublingual 3-5 minutes Intramuscular 10-20 minutes Subcutaneous 15-30 minutes Rectal 5-30 minutes Ingestion 30-90 minutes Transdermal (topical) variable (minutes to hours) Thanks!!