The Warnings and Precautions section on the safety labels of the antibiotic azithromycin, which includes the brand-name drugs Zmax and Zithromax, used to treat viral infections, has been updated to include a new subsection regarding the risk of infantile hypertrophic pyloric stenosis (IHPS).
IHPS is a condition in which the opening between the stomach and small intestine thickens, causing the pylorus muscles to block food from entering the small intestine. This can lead to forceful vomiting, dehydration and weight loss. It occurs most often in babies younger than 6 months of age and most often in males.
“Following the use of azithromycin in neonates (treatment up to 42 days of life) IHPS has been reported,” the new warning states. “Direct patients and caregivers to contact their physician if vomiting or irritability with feeding occurs.”
IHPS is treated with surgery, called pyloromyotomy, during which the surgeon cuts through the outside layer of the thickened pylorus muscle, allowing the inner lining to bulge out, providing a channel for food to pass through to the small intestines. The procedure is typically done with a laparoscope.
Any side effects in patients treated with azithromycin should be reported to the Food and Drug Administration (FDA) MedWatch Adverse Event Reporting Program at www.FDA.gov/MedWatch/Report.htm.