In vitro activity and pharmacokinetics of cefaclor in normal volunteers and patients with renal failure.

In both Mueller-Hinton agar (MHA) and antibiotic medium no. 1 (AB1) cefaclor was more active than cephalothin or cephalexin against Enterobacteriaceae. Its activity was equivalent to cephalexin against S. aureus in MHA. Cefaclor was particularly active against P. mirabilis. The activity of this antibiotic was greated in AB1 than in MHA. The inoculum effect was pronounced for cefaclor when compared with cephalothin, but cefaclor retained greater activity even against the higher inoculum. In volunteers with normal renal function, cefaclor produced slightly lower blood levels than those reported for cephalexin. Absorption after eating was decreased and delayed. Despite severe renal failure, substantial urine levels of antibiotic were still achieved. In contrast to cephalexin, plasma half-life for cefaclor was only moderately prolonged by renal failure (two-to-threefold) and only minimally shortened by haemodialysis. Adequate concentrations of cefaclor in sputum, active against common respiratory pathogens, could not be consistently demonstrated after the oral administration of a 1 gram dose of cefaclor.