Optimal dosing interval for penicillin treatment of streptococcal pharyngitis.

One-hundred-forty-two children with symptomatic pharyngitis had throat cultures positive for group A beta-hemolytic streptococci (GABHA). All were treated orally with penicillin V for ten days. Patients were randomly assigned to receive daily doses of 250 mg four times daily, 500 mg twice daily, or 1000 mg once daily. They were followed four weeks for either recurrent symptomatic pharyngitis or asymptomatic repeat positive throat culture. Patients treated two or four times daily had comparable outcomes. Children given penicillin once daily were more likely to have persistent positive culture after 48 hours treatment (5 of 48 or 10.4% vs. none of 94, p = .004) and more likely to have recurrent positive cultures after end of treatment (10 of 43 or 23% vs. 8 of 94 or 8%, p = .04). The treatment regime of penicillin V 500 mg twice daily is recommended for treatment of pharyngitis due to GABHS.