Pharmacology Flashcards
What is pharmacokinetics?
The movement of drugs within the body
How the body affects the drug including absorption, distribution, metabolism and excretion
What does pharmacokinetic absorption refer to?
The process of how the drug gets into the bloodstream
Speed of absorption determines onset of action
What are 5 factors that affect absorption?
Route of administration
Formulation/properties (solubility, size, preparation),
Blood flow to administration site
Drug interactions
Ability of drug to cross biological barriers
What route of administration is subject to first pass metabolism?
PO
What route gives immediate and complete bioavailability?
IV
What routes can give local +/- systemic effects?
TD
INH
PR
T (not really systemic)
IN
NEB
What routes are considered rapid?
IV
INH
SL
IN
NEB
What is bioavailability?
The amount of drug that reaches systemic circulation and is available to produce effect
Affected by absorption
What is pharmacokinetic distribution?
How the drug spreads throughout the body and to the site of action once it has been absorbed into the bloodstream
What are 6 factors that affect distribution?
Blood flow to area (more blood = more drug carried)
Tissue permeability (how well drug can cross barriers - lipophilic cross membranes better)
Protein binding (drugs bound to proteins are less distributable)
Blood brain barrier (only some drugs can cross)
Distribution to body compartments (may move to useless spaces e.g. extra cellular fluid)
Metabolism (may be converted to inactive metabolites in liver)
What is pharmacokinetic metabolism?
Process of drug transformation/break down
Affects duration of action and excretion
Primarily takes place in liver (also sweat, bile, renal, lung) via cytochrome P450 enzymes
What is a phase I metabolic reaction?
Drug is modified to make it more water soluble for easier excretion by kidney
What is a phase II metabolic reaction?
Combines drug with a compound to make it more water soluble for easier excretion by kidney
What is an enzyme induction/inhibition metabolic reaction?
Induction: drug increases activity of enzyme which leads to increased metabolism of other drugs
Inhibition: drug decreases activity of enzyme which leads to decreased metabolism of other drugs
What are 4 outcomes of drug metabolism?
Inactivation: converts drug to inactive metabolite
Activation: converts drug to an active form
Toxic metabolite: may convert to a toxic metabolite
Pharmacogenetics: individual genes may cause altered activity
What is pharmacokinetic excretion?
How the drug and metabolites are removed from the body
Primarily in the kidney (also liver, lung, gut and sweat)
What are 4 factors that can affect renal excretion?
Impaired renal function
pH of urine
Urine flow rate
Protein bound drugs less likely to be filtered
What are pharmacodynamics?
The effect that the drug has on the body and its mechanism of action
What are the 4 main interactions that drugs have with receptors?
Agonist: activates the receptor
Antagonist: blocks the receptor from being activated
Partial agonist: binds weakly and partially activates (weak response)
Inverse agonist: binds to receptor and stabilises them in an inactive state producing the opposite affect of an agonist
What is the difference between a side effect and an adverse effect?
Side effect is a more predictable result of a drug, may not result in harm
Adverse effect is an unpredictable result from a drug that causes harm
What is specificity?
Extent to which a drug selects its intended receptor site
What is affinity?
The strength of the bond between the drug and receptor site
What is potency?
The relative quantity of drug required to produce the intended effect on the body
What is efficacy?
The extent to which a drug produces the maximal effect
