Parmacokinetics of benzathine penicillin in the treatment of early syphilis in Zambia patients

Abstract

The study comprises 15 male patients between the ages of 20 and 29 years. Bacteriological examination established a definite diagnosis of early syphilis. Baseline studies like full blood count, ESR and random blood sugar, blood urea and electrolytes, serum creatinine and liver function tests were carried out on each patient. The patients were given a single injection of benzathine penicillin G, 2.4MIU intramuscularly. Blood was collected at intervals of 8, 24, 48, 72 hours, 7th, 14th and 28th day after injection of penicillin. Serum was separated and penicillin assay carried out on each sample. Peak serum levels of an average of 0.135IU/ml were established between 24-48 hours. The levels gradually dropped in the following weeks to 0.049 - 0.082 lU/ml on the 28th day. Thus showing that treponemicidal concentrations were maintained for sufficiently long periods.Pharmacokinetic analysis was carried out with the assumption that penicillin behaves in the body in a first-order fashion (one compartment model). The Ka which is the absorption rate constant was 4.063 min and the half-life was 39.7 hours. The results have been discussed in detail.