Pharmacology: Part II

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Pharmacology Part II

• determinants of drug effects

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Absorption

• Concentration of the drug
• dose response curve (ED, TD, LD)
• therapeutic index (TD1ED99)
• Solubility in water
• Surface area where absorption takes place

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Absorption

• Route of administration
• Blood flow
• pH gradient between drug and the absorption
  surface

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Route of Administration
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Distribution

• Patterns
• largely within blood stream (coumadin)
• uniformly throughout the body (alcohol)
• unevenly, dependent on membrane permeability
  (penicillin)
• concentrated in one or more body tissues / organs
  (nitroglycerine)
• Bioavailability
• bioequivalence (Note. generics)

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Distribution

• Combination with blood plasma proteins
• low affinity (sulfa drugs, antibiotics, alcohol,
  aspirin)
• high affinity (marijuana, phenobarbital,
  psychedelics, narcotics)
• Lipid solubility (marijuana, vitamins A, D, E
  K)
• Bioequivalence (Note. generics)

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Distribution

• Influence of other drugs and foods
• tetracycline and antacids / milk
• antihypertensives and licorice
• antidepressants (MAO inhibitors) and aged foods
  (wine, cheese, etc.)
• Cerebral blood flow, influenced by brain
  stimulation
• Blood-brain barrier

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Drug-Drug Interactions

• Independent - no apparent influence on effects
• Antagonistic - one drug inhibits the effects of
  the other
• Additive - combining of effects, usually by
  chemically similar drugs

• Potentiation - exagerration of effects of one
  drug due to the presence of another
• Synergism - exagerration of effects for both
  drugs

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Detoxification Removal

• Enzyme systems
• liver
• blood plasma
• kidneys
• General process

Active Drug Substances (non-polar)
Inactive Substances (polar)
Exceptions codeine psychedelics
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Other Key Principles

• Tolerance
• Withdrawal
• Rebound effects

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Other Key Principles

• Rebound effects

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Determinants of Drug Responsiveness Human

• Age
• immature enzyme systems
• impaired enzyme systems
• Height and Weight (as they relate to blood
  volume)
• Gender
• metabolic rate differences
• hormonal variations

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Determinants of Drug Responsiveness Human

• Biological rhythms
• insulin and blood sugar
• allergy medications and sleep cycle
• caffeine and energy levels
• Genetic predisposition
• Physiological state
• Placebo effect

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Determinants of Drug Responsiveness Environment

• Physical environment
• ambient temperature
• crowding conditions
• novelty of experience
• level of illumination, sound, etc.
• Task variables (e.g., need for concentration)