Local Anesthetic
PREGNANCY RECOMMENDATION: Limited Human Data—Probably Compatible
BREASTFEEDING RECOMMENDATION: No Human Data—Probably Compatible
PREGNANCY SUMMARY
A 1988 review concluded that the available human pregnancy data for tetracaine were inadequate to estimate the embryo–fetal risk from use of the local anesthetic in pregnancy (1). Animal reproduction data also are very limited but did not indicate risk. However, the highest dose used was equal to the human dermal dose based on BSA. In addition, there are no studies regarding the amount of tetracaine reaching the systemic circulation after topical (other than the skin patch) or spinal administration. Nevertheless, based on very small numbers, tetracaine does not appear to represent a risk of embryo and/or fetal harm any greater than that of other local anesthetics (see also Lidocaine, Pramoxine, and Ropivacaine). Thus, although the combined data are inadequate, the risk of embryo–fetal harm from tetracaine is probably low.
FETAL RISK SUMMARY
Tetracaine is an ester type local anesthetic agent. Because of the potential for severe systemic toxicity, its use is restricted to topical anesthesia and spinal block. For some procedures, injectable lidocaine is considered to be a safer alternative (2). Tetracaine is available as topical preparations (concentrations) that include solutions (2%), gels (2%), creams (1% and 2%), and ointments (1%), ophthalmic solutions (0.5%), and formulations for spinal anesthesia (0.2%, 0.3%, and 1%). It is also available in equal combination (70 mg each) with lidocaine as a skin patch that is indicated for use on intact skin to provide local dermal anesthesia for superficial venous access and superficial dermatological procedures such as excision, electrodessication, and shave biopsy of skin lesions (3). Little, if any, tetracaine is absorbed from the skin patch. Plasma levels of the anesthetic were not detectable (<0.9 ng/mL) at 30 and 60 minutes, whereas lidocaine was detectable in the plasma (<5 ng/mL) (3).
Reproduction studies have been conducted in rats and rabbits. In these species, SC doses up to the single dermal administration dose based on BSA (SDAD) were not teratogenic. In addition, no other reproductive or developmental toxicity was observed when tetracaine was given during gestation and lactation at a SC dose that was equal to the SDAD. Tetracaine has not been studied for carcinogenicity, but tests for mutagenicity were negative. The anesthetic agent had no effect on male and female rat fertility at SC doses up to the SDAD (3).
The low molecular weight (about 264) suggests that tetracaine crosses the human placenta, as does lidocaine and other local anesthetics (see Lidocaine). However, the amounts in the systemic circulation appear to be very low, at least from the skin patch, so the amount reaching the embryo and/or fetus will also be very low. Although the absorption of tetracaine into the blood from other formulations is unknown, it also is probably low.
The Collaborative Perinatal Project monitored 50,282 mother–child pairs, 23 of whom had exposure to tetracaine during the 1st trimester (4, pp. 358, 360). No evidence of an association with malformations was found.
A 1981 report described 53 women who received spinal anesthesia with tetracaine diluted to 0.5% (5). Prolongation of the induction-to-delivery interval had no effect on the Apgar scores or the neonatal acid-base values. However, when the uterine incision-to-delivery interval was more than 3 minutes, there were significantly lower mean pH and pO2 values in the umbilical vein and artery, and significantly higher mean pCO2 and base deficit results in the umbilical artery. Moreover, the prolonged interval was also associated with significantly more Apgar scores less than 7 at 1 and 5 minutes (5).
BREASTFEEDING SUMMARY
No reports describing the use of tetracaine during human lactation have been located. The low molecular weight (about 264) suggests that tetracaine will be excreted into human breast milk, as does lidocaine. (See Lidocaine.) However, the amount of tetracaine in the systemic circulation appears to be very low, at least from the skin patch, so the amount excreted into breast milk will also be very low. Although the absorption of tetracaine into the blood from other formulations is unknown, it also is probably low. Based on these estimates, the risk to a nursing infant from tetracaine given to the mother appears to be nil.
References
1.Friedman JM. Teratogen update: anesthetic agents. Teratology 1988;37:69–77.
2.Sweetman SC, ed. Tetracaine. Martindale: The Complete Drug Reference. 34th ed. London: Pharmaceutical Press, 2005:1385.
3.Product information. Synera. Endo Pharmaceuticals, 2007.
4.Heinonen OP, Slone D, Shapiro S. Birth Defects and Drugs in Pregnancy. Littleton, MA: Publishing Sciences Group, 1977.
5.Datta S, Ostheimer GW, Weiss JB, Brown WU Jr, Alper MH. Neonatal effect of prolonged anesthetic induction for cesarean section. Obstet Gynecol 1981;58:331–5.