Azlocillin serum levels on repetitive dosage in patients with normal and abnormal renal function

Azlocillin serum concentrations were followed in 9 severely ill patients with various degrees of renal dysfunction after single and repetitive dosage. All patients were treated concomitantly with a cephalosporin and/or an aminoglycoside antibiotic. Elimination halflives (t_1/2β) were highly variable (62-1,194 min), but no significant increase occurred in patients with stable renal function during repetitive dosage due to previously described nonlinear pharmacokinetic behavior of azlocillin. However, drug accumulation was observed in patients with deterioration of renal and hepatic function. The rise in drug accumulation can be disproportionally high if both routes of elimination are affected. In such cases, careful dosage adjustment of azlocillin is required to avoid toxic side effects.