Excretion of Drugs - Pharmacokinetics

Excretion of Drugs

·        Excretion:

o   Major routes renal, hepatobilary, pulmonary

o   Minor routes: saliva, breast milk, tears

·        Renal:

o  Few are excreted unchanged.  Lipid soluble undergo tubular reabsorption 

o  Only unbound particles excreted Þ if highly bound then slower excretion

o  Some are secreted by active tubular secretion e.g. penicillin, digoxin 

o  Urine pH: alkaline urine ® ­weak acid excretion (eg salicylates) and visa versa

·        Bilary:

o  Polar drugs likely to be excreted in bile, e.g. rifampicin, ampicillin

o  Some drugs undergo entero-hepatic circulation, e.g. oestrogens