Maternal and infant use of erythromycin and other macrolide antibiotics asrisk factors for infantile hypertrophic pyloric stenosis

Objectives: To evaluate the risk for infantile hypertrophic pyloric stenosi s (IHPS) among infants prescribed systemic erythromycin, infants prescribed a course of erythromycin ophthalmic ointment, and infants whose mothers we re prescribed a macrolide antibiotic during pregnancy. Study design: Retrospective cohort study of infants born at an urban hospit al from June 1993 through December 1999. Results: Of 14,876 eligible infants, 43 (0.29%) developed IHPS. Infants pre scribed systemic erythromycin had increased risk of HIPS, with the highest risk in the first 2 weeks of age (relative risk = 10.51 for erythromycin in first 2 weeks, 95% CI 4.48, 24.66). Erythromycin ophthalmic ointment for c onjunctivitis was not associated with increased risk of IHPS. Maternal macr olide antibiotics within 10 weeks of delivery may have been associated high er risk of IHPS but the data were not conclusive. Conclusions: This study confirms an association between systemic erythromyc in in infants and subsequent HIPS, with the highest risk in the first 2-wee ks of age. No association was found with erythromycin ophthalmic ointment. A possible association with maternal macrolide therapy in late pregnancy re quires further study. Systemic erythromycin should be used with prudence in early infancy.