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.

Options

1. Diclegis (10 mg of pyridoxime + 10 mg of doxylamine)
• 2-4 tablets qday usually before bed
  
• Should be taken on daily, scheduled basis for maximum effect
  
2. OTC (cheaper)
   
• Unisom Sleep Tabs (doxylamine) - 20 mg per tab
• Vitamin B6 (pyridoxime) - 25 mg per tab
• Take one of each tablet before bed
• Should be taken on daily, scheduled basis for maximum effect
  

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).

References:

(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.