Nausea and Vomiting of Pregnancy.

Because nausea and vomiting of pregnancy peaks at about 8 weeks, right in the middle of organogenesis, some physicians worry about prescribing drugs to pregnant women, including those that have been shown to be safe in pregnancy.

In my opinion, all the antiemetic drugs can be used in pregnancy with the exception of corticosteroids and marijuana, as their benefits outweigh their risks.

I consider the combination of the antihistamine/anticholinergic doxylamine and pyridoxine (vitamin [B.sub.6]) to be the firstline pharmacologic treatment of nausea and vomiting of pregnancy (NVP). These were the components of Bendectin, which was withdrawn by the manufacturer from the U.S. market in 1983 because of adverse publicity and litigation surrounding allegations that it was as sociated with limb reduction defects in babies exposed in utero. But in 1999, thc Food and Drug Administration deter mined that it was not withdrawn for safety reasons and added the combination back to its list of approved drug products that are considered safe and effective.

Bendectin is probably the most thoroughly studied drug combination in human pregnancy Among the estimated 30 million pregnant women who took Bendectin, no increase in or clustering of birth defects were detected.

Until this combination is available again in the United States, NVP can be treated with doxylamine, the over-the-counter nighttime sleep aid marketed as Unisom. One half of a 25-mg Unisom tablet can be taken with 25 mg of vitamin [B.sub.6] once or twice a day (Bendectin contained 10 mg of doxylamine and 10 mg of vitamin [B.sub.6] and was a slow-release formulation.)

Other antihistamines are also generally safe during pregnancy Still, all antihistamines should be avoided if premature labor occurs because, of a possible association between retrolental fibroplasia in premature babies exposed to antihistamines within 2 weeks of birth.

If intravenous therapy is necessary diphenhydramine (Benadryl) is the 'parenteral drug of choice. It is safe during pregnancy, although neonatal withdrawal has been reported with chronic use. Diphenhydramine also interacts with temazepam (Restoril), and has oxytocic properties when administered intravenously near term.