Recently, the InfantRisk Center was asked to comment on the use of a new, extended-release bupivicaine product called Exparel. This drug is applied to surgical wounds and provides local anasthesia over then next 3-4 days. Some doctors are beginning to use it with C-sections and have some concerns about its safety profile in breastfeeding mothers. This is what we said:
The available pharmacokinetic data on Exparel suggests that 266 mg produces an immediate peak (due to a small amount of "extraliposomal" bupivacaine in the formulation) which drops off at 2 hrs to a plateau of around 360 ng/mL. The elimination half-life of liposomal bupivacaine varies by route of administration between 12 and 34 hours.
During early postpartum (colostral phase), the lactocyte barrier is not fully formed and the milk/plasma ratio of most drugs is near 1:1. During this period, mothers only produce an average of about 60 mL of colostrum per day, thus the doses of many drugs is minimal during this phase.
Obviously, circulating bupivacaine derived from Exparel is no different from regular bupivacaine, commonly used in epidurals. Assuming a sustained plasma level of 360 ng/mL in both milk and plasma, only 21 mcg / day of bupivacaine would be delivered to the infant. The oral bioavailability of bupivacaine is not known, but using lidocaine as a model (~30%), then 7 mcg per day may end up in the infant's plasma. In addition, the volume of distribution for bupivacaine is high (0.4-1.0 L/kg), implying that plasma levels in the baby will be very low with this level of exposure.
Toxic effects are first seen in adults at around 2000 ng/mL.
It is our opinion that plasma levels in the baby are highly unlikely to come anywhere close to this. In summary, we believe that use of Exparel at these dosages is probably compatible with breastfeeding without restriction.
James Abbey, MD and Thomas W. Hale, Ph.D.
Hu D, Onel E, Singla N, Kramer WG, Hadzic A. Pharmacokinetic profile of liposome bupivacaine injection following a single administration at the surgical site. Clin Drug Investig. 2013 Feb;33(2):109-15. PMID: 23229686.