To : Georgeanne RE : Lidocaine This is from an upcoming article i've just finished on anesthetics: Lidocaine enters milk to a limited degree. In one study of a breastfeeding mother who received IV lidocaine for ventricular arrhythmias, the mother received approximately 965 mg over 7 hours including the bolus starting doses(Zeisler 1986). At seven hours, breastmilk samples were drawn and the concentration of lidocaine was 0.8 mg/L, or 40% of the maternal plasma level (2.0 mg/L). Assuming that the mother's plasma was maintained at 5 µg/mL (therapeutic = 1.5-5 µg/mL), an infant consuming 1 L per day of milk would ingest approximately 2 mg/day. This amount is exceedingly low in view of the fact that the oral bioavailability of lidocaine is very poor (35%). The lidocaine dose recommended for pediatric arrhythmias is 1 mg/kg given as a bolus. Once absorbed by the liver, lidocaine is rapidly metabolized. These authors suggest that a mother could continue to breastfeed while on parenteral lidocaine. Lidocaine has a brief half-life of 1.8 hours...so most would be gone in 8-10 hours for sure. Regards Tom Hale, Ph.D.