Erythromycin therapy for group A streptococcal pharyngitis. Results of a comparative study of the estolate and ethylsuccinate formulations.

One hundred two children with group A streptococcal pharyngitis were treated on a randomized basis with either 15 mg/kg of erythromycin estolate or 25 mg/kg of erythromycin ethylsuccinate given twice daily for ten days. Twelve patients, including 11 erythromycin ethylsuccinate-treated patients and one erythromycin estolate-treated patient, were dropped from the study at the request of their parents because of abdominal cramping and/or nausea and vomiting that occurred 15 to 45 minutes after ingestion of drug. Eighteen other patients (12 treated with erythromycin ethylsuccinate and six treated with erythromycin estolate) had similar gastrointestinal (GI) tract symptoms that resolved or abated. Excluding patients with reinfections with new streptococcal serotypes and those with resistant strains, the bacteriologic failure rates were 4.3% and 17.5%, and the total failure rates were 6.4% and 35.3% with erythromycin estolate therapy and with erythromycin ethylsuccinate therapy, respectively. The high rate of GI tract intolerance associated with the erythromycin ethylsuccinate appears to be dose related.