Oral Cephalexin and Ampicillin: Antimicrobial Activity, Recovery in Urine, and Persistence in Blood of Uremic Patients

A new orally absorbed cephalosporin derivative (cephalexin) and potassium ampicillin were studied in subjects with normal and decreased renal function. A 1-week course of each drug gave adequate therapeutic blood and urinary concentrations, without evidence of cumulation or toxicity in normal subjects. Almost all of the cephalexin and about one half of the ampicillin were recovered in the urine. The same treatment in uremic patients was associated with elevated concentrations of both drugs in the serum with only modest accumulation over 1 week. Concentrations in urine progressively rose and were adequate for most urinary tract organisms against which these agents are active. One of five patients had a fall in creatinine clearance 2 weeks after the last dose of cephalexin, but renal function later improved, and the effect cannot be proved drug-related. Both cephalexin and ampicillin may be useful in treatment of urinary infections in moderately uremic patients whose creatinine clearance exceeds 9 to 10 ml/min.