Antidote
PREGNANCY RECOMMENDATION: Compatible—Maternal Benefit >> Embryo–Fetal Risk
BREASTFEEDING RECOMMENDATION: Hold Breastfeeding
PREGNANCY SUMMARY
Reproduction studies with pralidoxime have not been conducted and the human pregnancy experience is limited to two cases. No other reports describing the use of this drug in human pregnancy have been located. Although the risk this agent represents in pregnancy cannot be assessed, the maternal benefit clearly outweighs any concern regarding embryo or fetal toxicity. Therefore, pralidoxime should not be withheld because of pregnancy.
FETAL RISK SUMMARY
Pralidoxime (2-PAM) reactivates cholinesterase (mainly outside of the CNS) that has been inactivated by phosphorylation due to an organophosphate pesticide or related compound. Its most critical effect is relieving the paralysis of the muscles of respiration. Pralidoxime is short-acting (apparent half-life 74–77 minutes) and is not bound to plasma proteins. Pralidoxime is available in an auto-injector that can be used rapidly in cases of exposure to nerve agents possessing anticholinesterase activity (organophosphate poisoning) (1).
Animal reproduction studies have not been conducted with pralidoxime.
It is not known if pralidoxime crosses the human placenta to the embryo or fetus. Pralidoxime chloride is a quaternary ammonium compound, but the molecular weight of the free base (about 137) is low enough for passage across the placenta. The rapid elimination of the drug should mitigate this transfer.
A 1988 report described the pregnancy outcomes of two women who were treated with pralidoxime for self-induced organophosphorus insecticide poisoning (2). In the first case, a 22-year-old primigravida at 36 weeks’ gestation was admitted to the hospital 3 hours after ingesting methamidophos. She was treated with pralidoxime and atropine and eventually recovered. Forty-four days after poisoning, she delivered a healthy 2.85-kg male infant with an Apgar score of 8 at 1 minute. The second case involved a 25-year-old woman at 16 weeks’ gestation who ingested fenthion. She also was treated with pralidoxime and atropine and made a full recovery. She delivered a healthy 3.83-kg infant (Apgar 10 at 1 minute) 24 weeks after intoxication (2).
BREASTFEEDING SUMMARY
No reports describing the use of pralidoxime during lactation have been located. Pralidoxime chloride is a quaternary ammonium compound, but the molecular weight of the free base (about 137) is low enough for excretion into breast milk. The rapid elimination of the drug should mitigate this transfer into milk. Moreover, the emergency nature of its use suggests that nursing is unlikely when it has been used. In any event, the maternal benefit is clear and breastfeeding should be held for at least 6–7 hours (about five half-lives) after a dose is given.
References
1.Product information. Pralidoxime Chloride Injection (Auto-Injector). Meridian Medical Technologies, 2002.
2.Karalliedde L, Senanayake N, Ariaratnam A. Acute organophosphorus insecticide poisoning during pregnancy. Hum Toxicol 1988;7:363–4.