A 28-year-old primigravida at 8 weeks of gestation presents with severe nausea and vomiting, unable to retain oral intake. Laboratory investigations show electrolyte imbalance and mild ketonuria. What is the drug of choice for managing hyperemesis gravidarum in this patient?

Explanation

## Drug of Choice for Hyperemesis Gravidarum **Key Point:** Metoclopramide remains the recommended first-line antiemetic for hyperemesis gravidarum (HEG) per ACOG and RCOG guidelines, owing to its dual prokinetic and antiemetic mechanism and well-established safety record in pregnancy. ### Mechanism of Action Metoclopramide is a **dopamine (D2) antagonist** with **prokinetic** properties. It accelerates gastric emptying and reduces nausea by blocking central and peripheral dopamine receptors — directly addressing the delayed gastric emptying that contributes to pregnancy-related vomiting. ### Safety Profile in Pregnancy - Historically classified FDA Category B; **note:** the FDA's 2020 label update flagged a risk of tardive dyskinesia with prolonged (>12 weeks) use, but **short-term use in pregnancy remains safe and is endorsed by ACOG/RCOG** - No established teratogenicity in first-trimester studies - Available in oral, IM, and IV formulations — particularly useful for hospitalized patients requiring parenteral therapy - Typical dose: 10 mg IV/IM/PO every 6–8 hours ### Why Not the Other Options? | Drug | Mechanism | Role in HEG | Notes | |------|-----------|-------------|-------| | **Metoclopramide** | D2 antagonist + prokinetic | **First-line** | Dual action; safe short-term; ACOG/RCOG endorsed | | Ondansetron | 5-HT3 antagonist | Second-line / adjunct | Effective for refractory cases; some studies suggest small cardiac septal defect risk in first trimester (conflicting data); more expensive | | Promethazine | H1 + anticholinergic | Alternative | Sedating; older safety data; less preferred | | Meclizine | H1 antagonist | Mild NVP only | Insufficient efficacy in severe HEG | ### Clinical Scenario Correlation This patient has **severe nausea/vomiting with electrolyte imbalance and ketonuria** — consistent with HEG requiring IV therapy. Metoclopramide 10 mg IV every 6–8 hours is the standard first-line parenteral antiemetic in this setting. **High-Yield:** Ondansetron is increasingly used in clinical practice, but per ACOG guidelines (Practice Bulletin 189) and Williams Obstetrics, **metoclopramide is the preferred first-line agent** for HEG, with ondansetron reserved for refractory or second-line use. **Clinical Pearl:** Avoid prolonged (>12 weeks) metoclopramide use due to tardive dyskinesia risk. For short-term inpatient management of HEG, it remains safe and effective. [cite: Williams Obstetrics 26e, Ch 4; ACOG Practice Bulletin No. 189 (2018)]