Ampicillin in Haemophilus influenzae meningitis. Clinicopharmacologic evaluation of intramuscular vs intravenous administration.

Sixty-two children with Haemophilus meningitis were treated with ampicillin sodium, 200 mg/kg/day for ten days. Thirty-one received the drug intravenously (IV) for ten days; the other 31 patients received ampicillin IV for five days (except for one test dose given intramuscularly [IM] on day 2) followed by IM administration of ampicillin the last five days. Ampicillin concentrations in cerebrospinal fluid (SCF) were higher one hour after IV administration, but at two and four hours, concentrations were greater after IM doses. Responses to therapy and rates of complications were similar in the two groups. Fourteen patients had positive CSF cultures on day 2. Ten of these were isolated only on Levinthal medium and would have been overlooked with routine culture methods. All organisms were ampicillin-susceptible and all CSF cultures were negative by 48 hours. More patients with delayed sterilization had neurologic sequelae (78%) than patients with prompt CSF sterilization (13%). The schedule of five days of IV treatment followed by five days of IM therapy was pharmacologically and clinically as effective as ten days of IV therapy and has practical advantages.