What is the comparative efficacy of promethazine (Phenergan) versus metoclopramide (Reglan) for treating nausea in pregnancy?

From the Guidelines

Metoclopramide is preferred over promethazine for nausea in pregnancy due to its better safety profile and efficacy, as evidenced by a recent study comparing the two medications, which found similar efficacy but fewer adverse events with metoclopramide 1. When managing nausea in pregnancy, it is essential to consider the potential risks and benefits of each medication.

• Metoclopramide, typically given at a dose of 10mg orally three times daily, has a better safety profile in pregnancy and is classified as FDA pregnancy category B, indicating no evidence of risk in humans.
• Promethazine, given at a dose of 12.5-25mg orally every 4-6 hours, is classified as pregnancy category C, meaning risk cannot be ruled out, and it causes more sedation, which can be problematic for pregnant women.
• Both medications should be used at the lowest effective dose for the shortest duration necessary, and non-pharmacological approaches like eating small, frequent meals, avoiding triggers, and ginger supplements should be tried first. The American College of Obstetricians and Gynecologists (ACOG) recommends a step-up approach for patients who do not respond to first-line therapy, with metoclopramide being a viable option for nausea and vomiting of pregnancy (NVP) and hyperemesis gravidarum (HG) 1. It is crucial to consult with an obstetrician before starting any medication during pregnancy to ensure appropriate management of maternal symptoms while minimizing fetal risk.
• In cases of severe nausea and vomiting of pregnancy, intravenous hydration and other medications like ondansetron may be necessary, and methylprednisolone can be given as a last resort in patients with severe HG 1.

From the Research

Comparison of Promethazine and Metoclopramide for Nausea in Pregnancy

• Both promethazine and metoclopramide are used to treat nausea and vomiting in pregnancy, with varying degrees of effectiveness 2, 3, 4, 5, 6.
• A study published in JAMA found that metoclopramide was associated with improved symptoms compared to placebo for mild symptoms, while promethazine was associated with improved symptoms for moderate symptoms 2.
• Another study published in the American Journal of Perinatology found that metoclopramide and ondansetron were both effective in reducing nausea and vomiting in pregnancy, with no significant difference between the two 3.
• A retrospective cohort study published in The American Journal of Emergency Medicine found no difference in time from medication administration to disposition between women who received ondansetron and women who received metoclopramide or promethazine 4.
• A double-blind trial published in the British Medical Journal found that metoclopramide and promethazine were equally effective in reducing nausea and vomiting in labor, but metoclopramide had a more favorable analgesic effect 5.
• A prospective multicenter international study published in the American Journal of Perinatology found that metoclopramide use during the first trimester of pregnancy was not associated with an increased risk of malformations, spontaneous abortions, or decreased birth weight, but was associated with a higher rate of premature births 6.

Efficacy and Safety

• The efficacy and safety of promethazine and metoclopramide for nausea in pregnancy have been evaluated in several studies, with mixed results 2, 3, 4, 5, 6.
• Metoclopramide has been shown to be effective in reducing nausea and vomiting in pregnancy, but its use has been associated with a higher rate of premature births 6.
• Promethazine has also been shown to be effective in reducing nausea and vomiting in pregnancy, but its use has been associated with a more persistent sedative effect 5.

Clinical Implications

• The choice between promethazine and metoclopramide for nausea in pregnancy should be based on individual patient needs and medical history 2, 3, 4, 5, 6.
• Healthcare providers should carefully weigh the potential benefits and risks of each medication and consider alternative treatments, such as ginger or vitamin B6, for mild symptoms 2.
• Further research is needed to fully understand the efficacy and safety of promethazine and metoclopramide for nausea in pregnancy and to identify the most effective treatment strategies for this common condition 2, 3, 4, 5, 6.