Lanthanum carbonate and sevelamer are indicated to reduce serum phosphate levels in patients with end-stage renal disease. The drugs bind dietary phosphate from food during digestion in the gut. There are no reports of their use in human pregnancy. The systemic bioavailability is minimal, and the drugs should have no effect on the embryo or fetus. However, they may prevent intestinal vitamin absorption, especially of fat-soluble vitamins.
The cholinergic agent physostigmine is capable of reversing the central nervous system effects of anticholinergics, such as scopolamine and tricyclic antidepressants. The reported human pregnancy experience is limited to the third trimester.
Methylene blue has been used for cyanide poisoning. In humans, it is teratogenic and fetal toxic when given by intra-amniotic injection, but its oral use as an antidote in pregnancy has not been reported. The cyanide antidote package contains amyl nitrite, sodium nitrite, and sodium thiosulfate. The effects of these agents on human pregnancy also are unknown, as are the effects of high-dose hydroxocobalamin, an analogue of vitamin B12 also used in cyanide poisoning.
Pralidoxime (2-PAM) reactivates cholinesterase that has been inactivated by organophosphate pesticides and chemicals with anticholinesterase activity, thereby relieving the paralysis of the muscles of respiration. The drug is available in an autoinjector that can be used rapidly in cases of exposure to nerve agents possessing anticholinesterase activity (organophosphate poisoning). Animal reproduction tests have not been conducted with pralidoxime, and the human pregnancy experience is limited to a few cases of insecticide poisoning (second and third trimesters). Healthy infants were later delivered in these cases.
Four antivenins are commercially available for acute envenomation: black widow spider antivenin, Centruroides (scorpion) immune F(ab\')2 (equine), crotalidae polyvalent immune Fab (ovine) (North American rattlesnake), and North American coral snake antivenin (equine). In addition, botulism antitoxin heptavalent (equine) is used for food poisoning caused by the neurotoxic bacterium Clostridium botulinum. Animal reproduction studies have not been conducted with these products, and human reports are limited or absent.
Sapropterin, a cofactor for the enzyme phenylalanine hydroxylase, reduces blood phenylalanine levels in patients with phenylketonuria. The drug is given daily if diet alone does not control maternal phenylalanine levels. Use of the drug in human pregnancy has not been reported.
A number of other agents can be classified as antidotes, in addition to their primary indications, because they can reverse the toxic effects of other agents. These antidotes include atropine (severe bradycardia, poisonings with organophosphates and carbamates), calcium chloride or gluconate (severe hypocalcemia, calcium-channel-blocker overdose, exposure to hydrofluoric acid), glucagon (hypoglycemia), folinic acid (methotrexate overdose), protamine (heparin overdose), pyridoxine (isoniazid-induced seizures; adjunct in ethylene glycol poisoning), and vitamin K (phytonadione) (warfarin overdose). The pregnancy data are extensive for many of these agents and are not suggestive of significant embryo or fetal risk.
Mr. Briggs is a pharmacist clinical specialist at the outpatient clinics of Memorial Care Center for Women at Miller Children’s Hospital in Long Beach, Calif.; clinical professor of pharmacy at the University of California, San Francisco; and adjunct professor of pharmacy at the University of Southern California, Los Angeles, and Washington State University, Spokane. He also is coauthor of "Drugs in Pregnancy and Lactation," and coeditor of "Diseases, Complications, and Drug Therapy in Obstetrics." He had no relevant financial disclosures. Contact him at obnews@frontlinemedcom.com.