Benzylpenicillin in mice. Effect of meningococci on plasma concentrations.

Plasma concentration studies were performed in mice given high intravenous (i.v.) bolus injections or subcutaneous (s.c.) depot doses of benzylpenicillin. There was a marked difference in plasma concentration within and between individuals both after benzylpenicillin (BP) given i.v. and after benzylpenicillin procaine (BPP) given s.c. BP given i.v. resulted in a plasma half-life of 15.2 minutes, while BPP given s.c. resulted in a plasma half-life of 2.7 hours. Infection with an endotoxin-liberating meningococcal strain in BP-treated animals increased the plasma levels of BP compared with uninfected controls.