Drug excretion Flashcards
where are drugs excreted mainly
liver and kidney
what is the name of the enzymatic system that most drugs use for metabolism?
P450 mono oxygenase system
what can p450 do?
drug metabolism - activate or inactivate dugs
drug interaction - competition for active sites can inhibit certain drugs, changing the efficacy and toxicity of the drug
prodrug activation
how are drugs eliminated
o Sweat
o Saliva
o Tears
o Renal excretion – urine
o Liver excretion – bile
o Lungs – gas
basis of drug testing
- Basis of drug testing , conc of drug in bodily fluids e.g. saliva will mirror drug conc in plasma
what to do if patient has renal or kidney disease?
reduce dosage, consult doctor , know about drugs that can cause further damage to kidney eg NSAIDs
plasma half life
time taken for half the drug to be eliminated
what is the differene is process of excretio between first and zero order kinetics
first oder - passive diffusion
zero order - active process
which kinetics has a constant half life?
first oder
which knetics has a fixed rate of excretion?
zero order, fixed rate irespective of drug conc
which kinetics has a log grpah that is linear
first order, increase drug conc = increase metabolis,
what happens if you administer too much drug in a zero order kinetix drug?
o If drug is administered at a faster rate than the fixed rate, saturation of receptors exceeded, accumulation of drug occurs
why do we need to balance intake with excretion? ie control the dosage
- Too frequent dosage – toxic plasma levels, liver cannot handle
- Too infrequent dosage – sub-therapeutic plasma levels, no clinical effect
why is oral route of absorption the least reliable?
git absorption varies too widely (acditiy , food, other drugs)
first pass metabolism
gastric acid inactivating drug
git problems
