A review of the rationale and advantages of various mixtures of benzathine penicillin G

Abstract

Intramuscular benzathine (BZ) penicillin G has been accepted as the gold standard for treatment of patients with streptococcal pharyngitis since it was first introduced in 1952. Unfortunately, it has been associated with pain and tenderness at the site of injection. Efforts to lessen this by combining it with varied quantities of procaine (PC) penicillin G have been successful, decreasing the incidence of significant local reactions to 5% to 10%, little more than that seen with PC penicillin alone. A preparation containing 600,000 U BZ penicillin G and 600,000 U PC penicillin in 2 mL has been marketed since the mid-1950s as CR Bicillin 600/600 but the content of BZ penicillin G has been considered adequate only for children who weigh < 60 pounds. This prompted the evaluation of a preparation containing 900,000 U BZ penicillin G plus 300,000 U PC penicillin G in a 2-mL injection. Of 400 children with streptococcal pharyngitis 100 each received this preparation, 600,000 U BZ penicillin G alone in 1 mL, 1.2 million U BZ penicillin G alone in 2 mL or 600,000 U BZ penicillin G plus 600,000 U PC penicillin G in 2 mL. Clinical response was equal in all four groups; all patients were well in 36 to 48 hours. The two preparations containing PC penicillin G had significantly less severe local reactions and throat cultures were negative in all by 48 hours; it remained positive in some patients who received BZ penicillin G alone after 72 hours. The cure rate in patients receiving the 900, 000/300,000 combination of BZ and PC penicillin G was equal to that in patients who received 1.2 million U BZ penicillin G with these added advantages. This combination offers optimal parenteral treatment for streptococcal pharyngitis in all children who weigh < 140 pounds and it has been marketed for this purpose since 1976.