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 micrograms/ml). Peak CSF levels were noted at 12 hours (0.70 +/- 0.35 microgram/ml). The serum level at 24 hours was 2.1 +/- 0.98 microgram/ml (range, 0.2 to 5.8 micrograms/ml); the CSF level at 24 hours was 0.12 +/- 0.05 micrograms/ml (range, 0.03 to 0.27 microgram/ml). These results demonstrate that spirocheticidal levels (greater than or equal to 0.03 microgram/ml) are achieved for at least 24 hours in the CSF following the intramuscular administration of aqueous procaine penicillin G in neonates.