Management of group a streptococcal pharyngitis: A randomized controlled study of twice-daily erythromycin ethylsuccinate versus erythromycin estolate

One hundred seventy-five children with Group A streptococcal tonsillopharyngitis received on a randomized basis erythromycin estolate (EE) (87 patients) or erythromycin ethylsuccinate (EES) (88 patients) in 15-mg/kg doses given twice daily. Patients ranged in age from 2 to 16 years and all were symptomatic when therapy was started. Treatment groups were similar with regard to age, sex, weight and duration of illness before therapy. All but three patients who had erythromycin-resistant streptococci improved within 24 hours of initiation of therapy. On the fifth day of therapy, Group A streptococci were present in throat cultures of 12 patients (5 EE, 7 EES); the serotypes of these organisms were identical to those isolated from pretreat-ment cultures, and 9 isolates were erythromycin-resistant. Four days after completion of treatment, Group A streptococci were cultured from 20 (24.7%) ethylsuccinate-treated and from 2 (2.4%) estolate-treated patients. All isolates were serotypically identical to the pretreatment or-ganisms. At 7 to 21 days after completion of therapy, streptococci were isolated from 8 patients (6 EE, 2 EES). New serotypes were present in 5 patients, all of whom were symptomatic. Excluding patients with new infections, the total bacteriologic failure rate was significantly (p < 0.001) larger for EES-treated (24.7%) than for EE-treated (5.1%) children. These results correlate with pharmacokinetic data demonstrating superior bioavailability and tonsillar concentrations of the estolate compared with those of the ethylsuccinate formulation.