1. Pregnant women randomized to receive ondansetron (Zofran) reported greater reduction in both nausea and vomiting than those who received doxylamine-pyridoxine (Diclegis).
2. The majority of women taking ondansetron (93%) experienced improvement in nausea compared to only 41% of women taking doxylamine-pyridoxine.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Nausea and vomiting during pregnancy is common, occurring in up to 80% of expectant mothers. More than just an inconvenience, severe nausea and vomiting of pregnancy can result in significant health consequences for both mother and child including dehydration, weight loss, and even rare complications like esophageal rupture. In addition to adverse health outcomes, nausea and emesis in pregnancy can lead to a host of psychological and economic burdens due to missed work time, increased health care visits, and strains on family dynamics. Pharmacologic management is sometimes recommended, but given the difficulty of conducting studies in pregnant women, limited data exists. Currently, the American College of Obstetricians and Gynecologists recommends a combination of pyridoxine (vitamin B6) and doxylamine (an antihistamine) as first-line therapy for nausea and vomiting in pregnancy. However, despite a lack of supportive evidence, the most frequently prescribed treatment in the United States is currently ondansetron, an antiemetic that blocks the 5-hydroxytryptamine type 3 receptor, thereby inhibiting the body’s vomiting center in the medulla oblongata.
In this study, researchers aimed to clarify whether ondansetron or pyridoxine-doxylamine was superior for the treatment of nausea and vomiting in pregnancy. Women in the ondansetron group were more likely to report a significant improvement in their nausea and vomiting as well as a greater median improvement in symptoms compared to the pyridoxine-doxylamine group. Strengths include rigorous randomized and blinded study design. Limitations include small sample size and homogenous study population (participants were recruited from a tertiary medical center that serves beneficiaries of active duty and retired military personnel). Further, a loss to follow-up rate of 22.2% in the ondansetron group compared to 5.6% in the doxylamine-pyridoxine group suggests that selection bias might bias results away from null (i.e. women who didn’t achieve success with ondansetron failed to follow up). Additionally, while data was collected on side effects, the study was only powered to detect differences in the primary outcome. Future studies might repeat a randomized controlled trial in a larger, more diverse population in order to better assess side effect differences between the two regimens.
In-Depth [randomized controlled trial]: Researchers recruited newly pregnant (<16 weeks gestation) women requesting treatment for nausea with or without vomiting and randomized them to receive either a combination of 25 mg pyridoxine and 12.5 mg doxylamine (n=18) or 4 mg ondansetron and a placebo pill (n=18). The dispensing pharmacist, provider, patient, and enrolling investigator were all blinded to the medication. Patients rated severity of nausea and vomiting using a visual analog scale (VAS) ranging from 0-100mm prior to taking the intervention and again after 5 to 7 days of treatment. Adverse effects, including constipation, headache, and sedation, were also subjectively assessed.
Women in the ondansetron group reported a greater reduction in nausea (p=0.019) and less vomiting (p=0.049) than those in the pyridoxine-doxylamine group. Women in the ondansetron group were more likely to report a significant improvement in their nausea (92.3% vs. 41.2%, p=0.007) and vomiting (76.9% vs. 35.3%, p=0.033). Four women were lost to follow-up in the ondansetron group (22.2%) compared to only one woman lost to follow-up in the doxylamine-pyridoxine group (5.6%)
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