Maternal Levels. Twelve mothers were given clarithromycin 250 mg orally twice daily for puerperal infections. Both clarithromycin and its active metabolite, 14-hydroxyclarithromycin, were found in milk. The peak clarithromycin milk level was 0.85 mg/L at 2.2 hours after the dose; the peak 14-hydroxyclarithromycin level was 0.63 mg/L at 2.8 hours after the dose. Respective trough values were 0.21 and 0.36 mg/L. The half-lives of the drug and metabolite were 4.3 hours 9 hours, respectively. Using the milk level data from this study, an exclusively breastfed infant would receive an estimated average of about 136 mcg/kg daily of drug plus metabolite with a maternal dosage of 500 mg daily. This dosage is less than 1% of the recommend pediatric (<6 months) dosage, and is about 1.7% of the maternal weight-adjusted dosage.. Clarithromycin Levels and Effects while Breastfeeding Summary of Use during Lactation Because of the low levels of clarithromycin in breastmilk and safe administration directly to infants, it is acceptable in nursing mothers.. Biaxin and Breastfeeding. Research on Biaxin (clarithromycin) and breastfeeding has shown that the medication does pass through breast milk in low amounts. These studies have also shown that Biaxin might increase the risk of hypertrophic pyloric stenosis in babies whose mothers are taking the drug while breastfeeding..