First Line Therapy For Hypermesis Gravidarum

Approximately 10% of women with nausea and vomiting in pregnancy require  medication. Such patients frequently present to the ED where antiemetc agents are commonly prescribed.

Randomized, placebo-controlled trials have shown the effectiveness of vitamin B6 (10 - 25 mg every 8 hours) in the treatment of hyperemesis gravidarum (1,2). A combination of vitamin B6 and the antihistamine doxylamine (Bendectin) was removed from the U.S. market in 1983 because of allegations of teratogenicity; these allegations were subsequently shown to be unjustified (1). This drug combination still remains available in  Canada (Diclectin), and its use has been  associated with a decreased incidence of hospitalization for nausea and vomiting in pregnancy (1).

Oral vitamin B6 and doxylamine (Unisom SleepTabs) are available over-the-counter in the US. This combination has been studied in more than 6000 patients and controls, with no evidence of teratogenicity and, in randomized trials, it has been associated with a 70% reduction in nausea and vomiting (1,3). It is recommended by the American College of Obstetricians and Gynecologists as first-line therapy for nausea and vomiting in pregnancy.

  1. Diclegis (10 mg of pyridoxime + 10 mg of doxylamine)
  2. OTC (cheaper)
If the symptoms start after 9 weeks of gestation other causes should be included on the differential diagnosis (usually starts around 6th week of pregnancy and may last until end of first trimester).


(1) Niebyl JR. Clinical practice. Nausea and vomiting in pregnancy N Engl J Med 2010 Oct 14;363(16):1544-50.
(2) Vutyavanich T, et al. Pyridoxine for nausea and vomiting of pregnancy: a  randomized, double-blind, placebo-controlled trial Am J  Obstet Gynecol 1995;173:881-884.
(3) ACOG (American College of Obstetrics and Gynecology) practice bulletin:  nausea and vomiting of pregnancy Obstet  Gynecol 2004;103:803-814.