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.