Lidocaine Pregnancy and Breastfeeding Warnings
Lidocaine is also known as: Anestacaine, DentiPatch, Dilocaine, L-Caine, Lidoject 1, Lidoject 2, Nervocaine, Truxacaine, UAD Caine, Xylocaine Dental Cartridges, Xylocaine Duo-Trach Kit, Xylocaine HCl, Xylocaine HCl For Spinal, Xylocaine-MPF
Lidocaine Pregnancy Warnings
Lidocaine has been assigned to pregnancy category B by the FDA. Animal studies have failed to reveal evidence of fetal harm. There are no controlled data in human pregnancies. Use in labor and delivery may result in fetal and neonatal toxicity. Lidocaine should only be given during pregnancy and in labor and delivery when need has been clearly established.
Lidocaine rapidly crosses the human placenta. Data have revealed that the average umbilical cord to plasma concentration ratio ranges from 0.5 to 0.7. The free fraction of lidocaine in neonates may be higher than in the mother due to decreased plasma protein binding. Decreased Apgar scores, apnea, fixed and dilated pupils, hypotonia, and seizures have been reported in some neonates whose serum levels were 2.5 mg/L or more. Some data have shown that neonates whose mothers received continuous lidocaine epidural anesthetic blocks had decreased muscle tone relative to neonates whose mothers received placebo. Other data have not supported this association. The placental transfer of lidocaine after prolonged continuous maternal IV administration has been described. After 14.1 g of lidocaine (50 mg/hr for 282 hours), the umbilical vein/maternal vein lidocaine concentration ratio averaged 0.52 (average maternal and umbilical vein concentrations of 1.6 and 0.83 mcg/mL, respectively). These data are similar to those described after shorter periods of administration of lidocaine during labor. The Collaborative Perinatal Project monitored 50,282 mother-child pairs, of whom 293 received lidocaine as a local anesthetic agent during lunar months one through four. Of the 293 pairs, 16 children with any malformation were born. Statistically, the overall standardized relative risk (SRR) of malformations was 0.85, indicating no association of this drug with broad classes of malformations. The only SRR greater than 1.5 was for the respiratory tract (2.02, based on three malformed children) and tumors (1.89, based on two malformed children). The statistical significance of these values are unknown. Data from the Michigan Medicaid Birth Defects Study has failed to reveal an association between the use of lidocaine and congenital abnormalities (written communication, Franz Rosa, MD, Food and Drug Administration, 1994). This was a retrospective study of 229,101 completed pregnancies between 1985 and 1992, of which 165 were exposed to lidocaine at some time during the first trimester, and 525 were exposed to the drug at any time during pregnancy. There were 7 total and 3 cardiovascular defects observed (6 and 3 were expected, respectively). There were two instances of polydactyly. There were no observations of cleft palate, spina bifida, limb reduction, or hypospadias. None of the observations achieved statistical significance. These data do not support an association between lidocaine and birth defects.
Lidocaine Breastfeeding Warnings
Limited data have shown that the average milk lidocaine levels were approximately 40% of maternal serum levels. In one case, a 37-year-old woman who had received two lidocaine boluses of 75 and 50 mg, then a continuous infusion of 2 mg per minute, had lidocaine levels of 2.0 and 0.8 mg/L in her serum and milk, respectively (milk to plasma concentration ratio of 0.4). The milk sample was obtained two hours after the lidocaine infusion was stopped. In another case, lidocaine and its metabolite, MEGX, were found in breast milk after injection of lidocaine 20 mg for a dental procedure. The milk to plasma lidocaine and MEGX concentration ratios in this case were 1.1 and 1.8, respectively.
Lidocaine is excreted into human milk. Side effects in the nursing infant are unlikely and would probably be limited to an idiosyncratic or allergic reaction. The manufacturer recommends caution when administering lidocaine to nursing women.
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