231 PHARMACOKINETICS OF AQUEOUS PENICILLINS IN CEREBROSPINAL FLUID OF NEONATES

Abstract

If central nervous system (CNS) involvement is suspected in congenital syphilis, both aqueous penicillin G (APG) and aqueous procaine penicillin G (APP) are recommended for treatment. To study pharmacokinetics after administration of APG and APP, single samples of cerebrospinal fluid (CSF) and serum of 21 infants treated for congenital syphilis were obtained 1½ to 6 hrs. following a single IM dose of 50,000 units/kg body weight. Only one baby was symptomatic. Serum levels and half-lives of APG and APP were within the ranges reported for term infants. Treponemacidal levels after APG (≥.03 ug/ml) were detected in 11 CSF specimens in the first sample at ½ hr. and persisted through the 6 hr. study. A peak CSF level of 0.17 ug/ml was found at 2½ to 3 hrs. with an estimated half-life of 1½ hrs. After APP, penicillin activity was not detected in 5 CSF samples between ½ to 1 hr., but was present by 1½ hrs. Only 2 of 9 samples reached APP levels of ≥.03 ug/ml; in these two, a peak of 0.08 ug/ml was reached at 2½ hrs. These preliminary data show that both penicillins will provide treponemacidal levels in the serum, but APG reaches a higher CSF level and persists for a longer time. APG appears to be a more appropriate drug for treatment of congenital syphilis with suspect or proven CNS involvement.

(^*Current address: UCLA Sch. of Med., Dept. of Pediatrics)

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