From the Editor

Optimal pharmacologic treatment of nausea and vomiting of pregnancy

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CASE: Pregnant patient seeks medication for her NVP

A 23-year-old G1P0 woman at 9 weeks’ gestation presents to your office with nausea and vomiting that is interfering with work. She has tried many changes in her daily habits. She has tried eating small, frequent meals; snacking on nuts and crackers; using lemon-scented products; and avoiding coffee and strong odors. Following an evaluation you diagnose nausea and vomiting of pregnancy (NVP). She asks, “Is there a medication for my nausea that is safe for my baby?”

Nausea with or without vomiting is a common problem for pregnant women between 6 and 14 weeks of gestation. In one study, nausea with or without vomiting was reported by 69% of patients and resulted in pharmacologic treatment in 15%.1 In a Cochrane review of NVP, investigators analyzed 37 trials involving treatments such as acupressure, acustimulation, acupuncture, ginger, chamomile, lemon oil, vitamin B6, and antiemetic medications. The authors concluded, “There is a lack of high-quality evidence to support any particular intervention.”2 Clinicians are challenged to effectively treat the symptoms of NVP and simultaneously to minimize the risk that the fetus will be exposed to a teratogen during the first trimester, a vulnerable period in organ development.

In this editorial, I briefly review nonpharmacologic options for NVP, but focus on current pharmacologic treatments. Of those available to ObGyns, what is the best first-choice treatment given recent and accumulated data regarding associated congenital anomalies?

Nonpharmacologic treatment
Although the authors of the Cochrane review did not identify high-quality evidence to support nonpharmacologic interventions, results of multiple randomized trials have demonstrated that ginger is effective in reducing pregnancy-associated nausea and vomiting.3 Ginger treatment is recommended at doses of 250 mg in capsules or syrup four times daily.

First-line pharmacologic treatment: Doxylamine plus pyridoxine
The US Food and Drug Administration (FDA) has approved the combination of doxylamine plus pyridoxine (vitamin B6) in a delayed-release formulation for treatment of NVP (­Diclegis). Doxy­lamine is an antihistamine that blocks H1-receptor sites in the chemoreceptor trigger zone. It also diminishes vestibular stimulation and depresses labyrinthine activity through central anticholinergic activity. Its elimination half-life is 10 to 12 hours (Lexicomp). Each tablet contains doxylamine 10 mg and pyridoxine 10 mg. The starting dose is 2 tablets at bedtime.

If the woman has persistent symptoms, a third tablet is added, to be taken in the morning. If symptoms continue, a fourth tablet is recommended to be taken in the afternoon. In a large, randomized clinical trial, doxylamine-pyridoxine treatment reduced nausea, vomiting, and retching and improved perceived quality of life compared with placebo.4 The FDA assigned doxylamine-pyridoxine pregnancy category A because of the extensive evidence that it does not cause an increase in fetal malformations.5,6

If the delayed-release doxylamine-pyridoxine formulation (Diclegis) is not available to the patient, alternative formulations of doxylamine and pyridoxine can be prescribed. Pyridoxine is widely available over the counter as 25-mg tablets, and one tablet can be prescribed two or three times daily. Doxylamine is available as a chewable prescription medicine in 5-mg tablets (Aldex AN) and two tablets can be prescribed two or three times daily. Doxylamine is also available as a 25-mg over-the-counter tablet in Unisom SleepTabs. One-half tablet can be prescribed two or three times daily. The patient should be alerted that Unisom SleepGels contain diphenhydramine, not doxylamine.

Second-line pharmacologic treatment
Metoclopramide Metoclopramide is a dopamine antagonist. It enhances upper gastrointestinal motility, accelerates gastric emptying, and increases lower esophageal sphincter tone. At higher doses it blocks serotonin receptors in the chemoreceptor trigger zone. Its elimination half-life is 5 to 6 hours (Lexicomp). There are no large, randomized, placebo-controlled trials of oral metoclopramide for the treatment of nausea and vomiting of early pregnancy.

I am recommending metoclopramide as a second-line treatment for NVP because it appears to be effective and is not known to be associated with an increased risk of congenital malformations. Metoclopramide is widely used to prevent and treat intraoperative and postoperative nausea associated with cesarean delivery.7 In addition, intravenous (IV) metoclopramide is commonly used to treat women hospitalized with hyperemesis gravidarum. Results of randomized clinical trials demonstrate that when used to treat hyperemesis gravidarum, IV metoclopramide (10 mg every 8 hours) has similar efficacy to IV ondansetron (4 mg every 8 hours)8 and IV promethazine (25 mg every 8 hours).9 When using metoclopramide as an oral treatment for NVP, 10 mg every 8 hours is a commonly recommended regimen.

The FDA has assigned metoclopramide to pregnancy category B, which indicates that there is no evidence of fetal risk. Studies from Israel and Denmark show that metoclopramide is not associated with an increased risk of congenital malformations. In the study from Israel, among 3,458 infants born to women who had filled a prescription for metoclopramide during the first trimester of pregnancy, there was no increase in major congenital malformations, low birth weight, preterm delivery, or perinatal death.10 In the study from Denmark, among 28,486 infants born to mothers who had filled a prescription for metoclopramide in the first trimester there was no increase in congenital malformations or any of 20 individual categories of malformations, including neural tube defects, transposition of the great vessels, ventricular septal defect, atrial septal defect, tetralogy of Fallot, coarctation of the aorta, cleft lip or palate, anorectal atresia/stenosis, or limb reduction.11 The results of these two large studies are reassuring that metoclopramide is not associated with an increased risk of congenital malformations.

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