Effect of analgesic nephropathy in women on the metabolism and excretion of 14C-acetaminophen.

Nephropathy due to excessive consumption of phenacetin-containing analgesic mixtures has been a problem in Canada. Following the withdrawal of phenacetin it seems probable that acetaminophen consumption will increase and this study investigated the metabolism of 14C-Acetaminophen in patients with nephropathy and in healthy women. The respective alpha T1/2s of excretion of Acetaminophen and its metabolites were 2.58 h in the controls, 4.28 h in patients with analgesic nephropathy and 6.53 h in patients with nephropathy due to causes other than analgesic abuse. Both groups of patients had T1/2s that were significantly longer than the controls. The total 12 h recovery of 14C was highly positively correlated with creatinine clearance. (R = 0.92, P less than 0.001). No significant shifts in metabolism were discernable. It is concluded that patients with either analgesic nephropathy or nephropathy due to other causes metabolise Acetaminophen normally but excretion is delayed in proportion to the degree of renal impairment.