Concentrations of ampicillin and chloramphenicol in the serum of patients with acute Salmonella enteric fever.

Concentrations of ampicillin and chloramphenicol were measured in the serum of patients being treated for acute infections by Salmonella typhi or S. paratyphi A. Ampicillin was administered by the oral or intramuscular routes, whereas chloramphenicol was given orally only. Ampicillin concentrations were highest 1 hr after initiation of intramuscular therapy and 2 hr after oral administration. The serum concentration of ampicillin was significantly higher when it was given intramuscularly than when it was given orally. However, serum concentrations in orally treated patients were approximately the same at 1 hr after the fifth dose as they were 1 hr after the first dose, in contrast to intramuscularly treated patients, in whom the serum concentration of ampicillin was significantly lower 1 hr after the fifth dose. On the other hand, serum concentrations of chloramphenicol were significantly higher after the fifth dose than after the first dose. The rates of cure, relapse, and drug treatment failure were similar for all treatment regimens, and the drug concentrations attained in serum were generally above the minimal inhibitory concentration for the infecting salmonellae.