Very early exposure to erythromycin and infantile hypertrophic pyloric stenosis.

OBJECTIVE To assess the link between very early erythromycin exposure and pyloric stenosis in young infants. DESIGN Retrospective cohort study. PARTICIPANTS AND METHODS Medicaid or TennCare (Tennessee's program for Medicaid enrollees and uninsured individuals) births in Tennessee from 1985 to 1997. Cases of infants with a hospital discharge diagnosis of pyloric stenosis and an associated surgical procedure code were used. Erythromycin exposure and other antibiotic exposure between 3 and 90 days of life were identified from prescription files. MAIN OUTCOME MEASURES Hospital discharge diagnosis of pyloric stenosis, and an associated surgical procedure code. RESULTS Of 933 239 births in Tennessee during the study period, 314 029 were enrolled in Medicaid. Among these infants, 804 (2.6/1000 infants) met the criteria for pyloric stenosis. Very early exposure to erythromycin (between 3 and 13 days of life) was associated with a nearly 8-fold increased risk of pyloric stenosis (adjusted incident rate ratio, 7.88; 95% confidence interval, 1.97-31.57). No increased risk of pyloric stenosis was seen in infants exposed to erythromycin after 13 days of life or in infants exposed to antibiotics other than erythromycin. CONCLUSIONS The significant increase in pyloric stenosis in children with very early exposure to erythromycin is consistent with reports of other investigators. The risks and benefits of erythromycin should be weighed carefully prior to initiating such therapy in young infants.