Pharmacology: fate of drugs & terminology Flashcards
what are the different fates of drugs in the body
absorption, distribution, metabolism, excretion
what is absorption of a drug dependent on (4)
solubility, lipid : water coefficient, chemical stability, degree of ionisation(Henderson Hasslebach)
what is distribution of a drug dependent on
what body compartments drug can access
describe the distribution of drugs confined to plasma
too large to get past capillaries, or bound to plasma protein( e.g. heparin)
describe the distribution of drugs confined to interstitial fluid and plasma
can get past capillaries, but not lipid soluble so cant get past cell membrane (e.g. amoxicillin)
describe the distribution of drugs in all fluids
small and lipophilic, can get past cell membrane
e.g. ethanol
what are the 2 types of excretion
hepatic and renal
what is meant by the clearance of a drug
volume of drug cleared from the plasma in a unit of time
what is the half-life of a drug
time taken for the plasma conc. of the drug to reduce by half
what is meant by steady state dose
when rate of administration = rate of elimination
what is the benefit of a steady state dose and how many half lives is it achieved after
provides a constant plasma conc.
it is achieved after 5 half lives
what is the difference between IV and oral administration when trying to achieve steady state dose
IV = smooth curve Oral = peaks and troughs with steady state average
describe what the therapeutic window of a drug is
the window between the minimum effective conc.(MEC) and the maximum tolerated conc. (MTC)
bigger the better
briefly describe what zero order kinetics of a drug is
when it is excreted at the same rate regardless of plasma conc. ( straight graph)
briefly describe what first order kinetics of a drug is
when it is excreted at a rate proportionate to the dose/conc. in plasma ( curved graph)
