The combination of doxylamine succinate and pyridoxine hydrochloride (vitamin B6), to be marketed as Diclegis, has been approved by the FDA for the treatment of nausea and vomiting in pregnancy. A similar combination was previously sold under the name Bendectin but was pulled from the market in 1983 because there were concerns regarding its reproductive safety.  (Bendectin originally contained dicyclomine which was later removed due to lack of efficacy.)

Many obstetricians believe that Bendectin should never have been pulled from the market; in fact, the combination of doxylamine and pyridoxine continued to be sold in Canada under a different name (Diclectin).  And here’s some interesting history about Bendectin.  It turns out that Dr. William McBride, a high-profile expert witness hired for cases brought against Merrill-Dow, the manufacturer of Bendectin, was later found to have falsified research on the teratogenic effects of this drug.

Two separate meta-analyses have assessed pregnancy outcomes following first trimester exposure to the combination of pyridoxine and doxylamine (with and without dicyclomine).  The first meta-analysis, published in 1988, combined data from 12 cohort and 5 case-control studies, and the subsequent meta-analysis, published in 1994, combined data from 16 cohort studies and 11 case control studies. These studies included over 200,000 Bendectin-exposed pregnancies and did not observe an increased risk for major malformations.

We don’t yet know if Diclegis is effective for the management of hyperemesis gravidarum, a more severe form of nausea and vomiting; however, this will be a good option for pregnant women whose symptoms fail to respond to dietary and lifestyle modifications.

Ruta Nonacs,MDPhD

McKeigue PM, Lamm SH, Linn S, Kutcher JS. Bendectin and Birth Defects: I. A Meta Analysis of the Epidemiologic Studies. Teratology. 1994;50:27-37.

Einarson TR, Leeder JS, Koren G. A Method for Meta-Analysis of Epidemiological Studies. Drug Intell Clin Pharm. October 1988;22(10):813-824.