Amdinocillin pharmacokinetics. Simultaneous administration with cephalothin and cerebrospinal fluid penetration

In the treatment of serious infections, combinations of beta-lactam antibiotics are being utilized in order to avoid aminoglycoside toxicity and to achieve antibacterial synergy. The pharmacokinetic disposition of amdinocillin and cephalothin was determined, when administered alone or in combination to healthy volunteers, as well as the penetration of amdinocillin into human cerebrospinal fluid. Six subjects received, on separate occasions, single intravenous doses of amdinocillin 10 mg/kg, cephalothin 15 mg/kg, or a combination of the two in the same doses. The elimination half-lives of amdinocillin and cephalothin are increased when these drugs are given simultaneously, compared with when they are administered alone. However, no significant differences were observed. When they were given in combination, no significant changes in plasma clearance, renal clearance, or steady-state volume of distribution were found. Eight patients undergoing lumbar puncture for various neurologic disorders without inflamed meninges received a single dose of 10 mg/kg amdinocillin intravenously. One to two hours later, simultaneous plasma and cerebrospinal fluid samples were obtained. The concentration of amdinocillin in the cerebrospinal fluid ranged from approximately 1 to 10 percent of concomitant plasma concentrations. Thus, amdinocillin penetrates in the cerebrospinal fluid in marginal amounts in the absence of meningeal inflammation.