Maternal Levels. A single oral dose of 650 mg of acetaminophen was given to 12 nursing mothers who were 2 to 22 months postpartum. Peak milk levels of 10 to 15 mg/L occurred between 1 and 2 hours after the dose in all patients. Acetaminophen was undetectable (< mg/L) in all mothers 12 hours after the dose. The authors calculated that an infant who ingested 90 mL of breastmilk every 3 hours would receive an average of mg of acetaminophen or % (range to %) of the mother's absolute dosage. Using data from this study, an infant would receive a maximum of about 2% of the maternal weight-adjusted dosage.