Clinical pharmacology of benzatbine penicillin G in neonates with regard to its recommended use in congenital syphilis

Benzathine penicillin G has been recommended by the Center for Disease Control and the American Academy of Pediatrics for treatment of congenital syphilis in spite of the lack of published data concerning clinical pharmacology and efficacy of the drug in this disease. Five newborn infants received a single intramuscular dose of 50,000 units per kilogram of benzathine penicillin G. Peak serum levels of 0.38 to 2.1 μg per milliliter were observed at 24 hours, and concentrations of 0.07 to 0.09 μg per milliliter were measurable at 12 days after the dose. Penicillin activity was not detected in three of four cerebrospinal fluid samples. Because of this latter finding and until studies of clinical efficacy are available, benzathine penicillin G cannot be recommeded for treatment of congenital syphilis. Aqueous penicillin G is the drug of choice.