Antidote
PREGNANCY RECOMMENDATION:Limited Human Data—No Relevant Animal Data (Maternal Benefit May Outweigh Any Embryofetal Risk)
BREASTFEEDING RECOMMENDATION:Hold Breastfeeding
One report describing the use of fomepizole during human pregnancy was located. A pregnant woman was treated with fomepizole twice during a pregnancy at 11 weeks’ gestation and again 6 weeks later for inhalation of carburetor cleaner. The cleaner contained a mixture of methanol, toluene, methylene chloride, and carbon dioxide. No adverse effects were reported with the treatments. However, she was lost to follow-up and the eventual pregnancy outcome was unknown. The drug will likely cross the placenta, so fetal exposure will probably occur. Therefore, this limited human pregnancy experience prevents a complete assessment of the embryofetal risk. Animal reproduction studies have not been conducted. Because these chemicals can be lethal, the maternal benefits of therapy are great and probably outweigh any potential embryofetal risk.
No reports describing the use of fomepizole during human lactation have been located. The drug will likely be found in breast milk, so infant exposure will probably occur. The effects of this exposure on a nursing infant are unknown. Breastfeeding while using this drug should be based on the mother’s clinical need for treatment. If used, the infant should be monitored for the most commonly reported adult side effects of headache, nausea, and dizziness (all leading to irritability). However, because these chemicals can be lethal, the maternal benefits of therapy are great. Breastfeeding should not prevent the use of fomepizole. Another option would be to hold breastfeeding temporarily (pump and discard the breast milk), at least until the therapy is completed. The time required to fully eliminate the drug is unknown. In addition, the poisons for which the drug would be used are ethylene glycol and methanol. The MW and mean elimination half-life of ethylene glycol are about 62 and 6 hours, respectively. The MW and elimination half-life of methanol are about 32 and 4 hours, respectively. Therefore, these poisons will most likely be found in breast milk. If the mother’s blood levels for these poisons become undetectable, then the amount in breast milk is likely to be negligible.