Cerebrospinal fluid concentrations of aqueous procaine penicillin G in the neonate

Simultaneous serum and CSF samples were obtained following the intramuscular administration of 50,000 units/kg of aqueous procaine penicillin G in 25 neonates. Penicillin activity was detected in the sera and CSF of all patients. Peak serum levels were noted at four hours (mean ± SEM, 17.1 ± 6.3 μg/ml). Peak CSF levels were noted at 12 hours (0.70 ± 0.35 μg/ml). The serum level at 24 hours was 2.1 ± 0.98 μg/ml (range 0.2 to 5.8 μg/ml); the CSF level at 24 hours was 0.12 ± 0.05 μg/ml (range, 0.03 to 0.27 μg/ml). These results demonstrate that spirocheticidal levels (≥0.03 μg/ml) are achieved for at least 24 hours in the CSF following the intramuscular administration of aqueous procaine penicillin G in neonates.