Opioid pharmacokinetics

ADME: Absorption, Distribution, Metabolism, Excretion A: IV - fast as no absorption phase, rapid increase in drug concentration in the brain. Oral - no euphoria, slow absorption, no sudden increase in drug concentration. D: CNS, crosses blood brain barrier (BBB) M: Liver - phase 1 (oxidation or hydrolysis), phase 2 (conjugation) - slow metabolism may cause overdose, may prolong drug effects E: kidneys - excreted as metabolites - depends on kidney function, reduced in elderly prolongs drug effects. Exception - methadone excreted via bile