## First-Line Uterotonic for Postpartum Hemorrhage **Key Point:** Oxytocin is the WHO-recommended first-line uterotonic for prevention and treatment of postpartum hemorrhage due to its rapid onset, predictable effect, and favorable safety profile. ### Mechanism of Action Oxytocin causes sustained uterine contractions through G-protein coupled receptor activation, leading to: - Increased intracellular calcium in myometrial cells - Sustained tetanic contractions that compress bleeding vessels - Onset within 2–3 minutes (IV) or 5–10 minutes (IM) ### Dosing in Postpartum Hemorrhage - **IV bolus:** 10 IU over 1–2 minutes - **IM injection:** 10 IU as single dose - **IV infusion:** 10–40 IU in 500 mL saline over 15–30 minutes for continued bleeding ### Advantages Over Other Uterotonics | Feature | Oxytocin | Ergotamine | Carboprost | Misoprostol | |---------|----------|-----------|-----------|-------------| | **Onset** | 2–3 min (IV) | 5–7 min | 1–2 min | 10–15 min | | **Duration** | 30–60 min | 3–6 hours | 2–3 hours | 3–4 hours | | **Contraindications** | Few | Hypertension, vasospasm | Asthma, PVD | Diarrhea, fever | | **Cost** | Low | Low | Higher | Low | | **WHO Recommendation** | **First-line** | Second-line | Third-line | Alternative | **High-Yield:** Oxytocin is preferred because it has the fastest onset when given IV, minimal side effects, and is universally available in resource-limited settings. **Clinical Pearl:** Ergotamine and carboprost are reserved for cases refractory to oxytocin; ergotamine is contraindicated in hypertensive patients (risk of eclampsia/stroke), and carboprost is contraindicated in asthma. **Warning:** Do NOT give ergotamine before delivery of the placenta — it causes tetanic uterine contraction and can trap the placenta or cause uterine rupture.
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