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Pharmacology _amp; Physiology of Drugs

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					Pharmacology &
Physiology of Drugs

How Drugs Work
But First….

   Drug Use as a Social Problem!!

   “Costs” of drug use to society
    – What are they???
The Big Change

   What made our government change
    from a “laissez-faire” attitude to one of
    control?
    – Toxicity
    – Dependence
    – Crime
Potency vs. Toxicity
 Potency: the amount of drug necessary to
 cause an effect

 Toxicity: the capacity of a drug to do damage
 or cause adverse effects in the body
Toxicity
What makes a drug toxic?
 • Amount used
 • How it is used
 • What the user did while on the drug
Examples of Drug-Induced Toxicity

   Acute
    – Behavioral – “intoxication” that impairs the
      user’s actions and increase the danger to
      themselves or others
    – Physiological – overdose that causes the user
      to stop breathing or for their heart to stop
Examples of Drug-Induced Toxicity
   Chronic
    – Social problems
      • Personality changing
      • Effects on friends and family
      • Change of lifestyle
    – Health problems
      •   Heart disease
      •   Lung cancer
      •   Liver danger
      •   Other health effects
Drug Abuse Warning Network

 A system for reporting incidences of lethal
  and non-lethal drug related emergency in
  some US metropolitan hospitals
 DAWN included improper use of
  prescription or over-the-counter drugs and
  the use of any other substance for psychic
  effect, dependence or suicide
Drug Abuse Warning Network

     What it tells us about how
      dangerous a drug is?

     What it does not tell us about how
      dangerous a drug is?
Blood Borne Diseases

 Specific toxicity for inject drugs
 AIDS, HIV and Hepatitis B and C
 Why do the blood borne diseases spread
  so rapidly with these drug users?
Brief Time-Out….

   Re-cap
    – We know drugs can be problematic
    – We know that drugs can have varying
      effects


    – What causes these different effects??
Factors Influencing Drug Effects

   Drug factors
    – Pharmacological properties
    – Dose-response
    – Time-action
    – Purity & potency
    – Drug history
    – Method of use
Dose-Response
   Factors:
    – Pharmacokinetic properties:
       • Rate of absorption
       • Manner distributed throughout the body
       • Rate of metabolized and eliminated
    – Form of the drug
    – Manner in which the drug is
     administered
Figure 5.2
Relationship between alcohol dose and multiple response
Potency vs. Toxicity (again!)

                Potency
      The amount of drug necessary
           to cause an effect.

                   Toxicity
The capacity of a drug to do damage or cause
        adverse effects in the body.
Toxicity and Effectiveness
   Assessing toxicity is calculated by:
    – LD-50, a statistic determined by animal testing
      using a wide-range of drug dosages and
      assessing toxicity (e.g. lethality)
   Assessing the margin of safety is determined
    by:
    – Calculating the difference between the
      therapeutically effective dose (ED-50) and LD-50
     Margin of Safety
The range in dose between
the amount of drug necessary
to cause:
•a therapeutic effect, and
•a toxic effect
        Potency



        Toxicity




   Margin of safety
Figure 5.3
Possible relationship between drug concentration in the
body and measured effect of the drug.
Factors Influencing Drug Effects

   User factors
    – Body mass
    – General health
    – Genetics
    – Age
    – Biochemical state
    – Expectations
Factors Influencing Drug Effects

   Social factors
    – Setting
    – Environment
So, What Happens When a Drug
Enters Your Body??
 Bloodstream
 Deposits in other tissues
 Central Nervous System (CNS)
                oral ingestion

   Forms
                   inhalation
and methods
     of
taking drugs        injection


               topical application
Figure 5.4
Distribution of drugs through the body
Major Body Systems Affected

 Endocrine
 Cardiovascular
 Respiratory
 Gastro-Intestinal
 Nervous
The Nervous Systems
   Somatic Nervous System
    – Sensory information
    – Voluntary actions

   The Autonomic Nervous System (ANS)
    – Sympathetic
    – Parasympathetic

   The Central Nervous System
    – The Brain
    – Chemical Pathways
Figure 4.3
Figure 4.4
Central Nervous System

 Brain & spinal cord
 Role of neurons
 Neurotransmitters
    – Chemical messengers
    – Synapse between neurons
Neurotransmission

 All nervous systems consist of
  specialized nerve cells called neurons
 Neurons are responsible for receiving
  and sending information
 Sending and receiving information is a
  highly specialized, precise and very
  rapid
Neurotransmission
 The receiving region of the neuron is
  affected by a chemical message that
  either excites or inhibits
 If the message is excitatory, an impulse
  moves from the receiving region of the
  neuron down the axon to the sending
  region, the terminal, and chemical
  messengers, neurotransmitters, are
  released
Figure 4.1
Every neuron has four regions: cell body, dendrites, axon,
presynaptic terminals.
   Specific Neurotransmitters
Neurotransmitter   Type of effect   CNS changes         Drugs of abuse
dopamine           inhibitory-      euphoria            amphetamines,
                   excitatory        agitation           cocaine
                                     paranoia
GABA               inhibitory       sedation            alcohol,
                                     relaxation          Valium-type
                                     drowsiness           barbiturates
                                     depression
serotonin          inhibitory       sleep               LSD
                                     relaxation
                                     sedation
acetylcholine      excitatory-      mild euphoria       tobacco,
                   inhibitory        excitation          nicotine
                                     insomnia
endorphins         inhibitory       mild euphoria       narcotics
                                     block pain
                                     slow respiration
Figure 4.7
How Drugs Work

   http://www.pbs.org/wnet/closetohome/s
    cience/html/whydrugs.html
Chemical Theories of Behavior




    The Chinese made the yin and the
    yang.
Brain Imaging Techniques

   PET-Position Emission Tomography

   MRI- Magnetic Resonance Imaging
Drug Effects—Review

        Age        Drug interactions
        Gender     Tolerance
        Dose       Setting
        Purity     Method of
        Potency     administration
   Mechanisms of drug action
    – Effects on all neurons
    – Effects on specific neurotransmitter
      systems



   Drug deactivation
    – Inactivation and elimination of drugs from
      the body
    – Metabolism and biotransformation
    – Half-life of a drug
Mechanisms of Tolerance and
Withdrawal Symptoms

 Drug   Disposition Tolerance
  – Increased metabolism reduces the
    effect of the subsequent dose
  – pH of urine
Mechanisms of Tolerance and
Withdrawal Symptoms
   Behavioral tolerance
    – Reduced effect on behavior


   Pharmacodynamic tolerance
    – Sensitivity of the neurons

				
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