Background: An interval of 3–4 weeks between intramuscular injections of 1.2 million units of benzathine penicillin G as prophylaxis against group A streptococcal infection is recommended by health organizations for patients with pediatric rheumatic fever and heart disease.
Methods: We reviewed the literature for evidence of the persistence of serum penicillin G during the first 4 weeks after the recommended dose of benzathine penicillin G.
Results: The weighted-mean concentration was <0.02 µg/mL by 3 weeks after the initial dose. Weighted means were lower in studies done after 1990 than before (P < 0.01), in studies dealing with secondary versus primary prophylaxis (P < 0.01) and in studies in children versus those in adults (P < 0.02).
Conclusions: Recommendations for benzathine penicillin G prophylaxis may need reevaluation.