1. Clinical Overview
Methylergometrine (also known as Methylergonovine) is a semi-synthetic ergot alkaloid derivative used primarily in obstetrics and gynecology as a potent uterotonic agent. It acts as a partial agonist at serotonin (5-HT2) receptors and a potent agonist at alpha-adrenergic receptors on uterine smooth muscle, leading to sustained, forceful contractions. In the Indian context, it is a critical drug for the management of postpartum hemorrhage (PPH), a leading cause of maternal mortality. It is often preferred over ergometrine due to its better side effect profile, particularly less pronounced vasoconstriction and emetic effects.
| Onset | Duration | Bioavailability |
|---|---|---|
| Oral: 5-10 minutes; Intramuscular (IM): 2-5 minutes; Intravenous (IV): Immediate (within 1 minute). | Oral/IM: Approximately 3 hours; IV: 45 minutes to 3 hours. | Approximately 60% after oral administration. |
2. Mechanism of Action
Methylergometrine induces rhythmic, forceful, and prolonged contractions of uterine smooth muscle. It increases the amplitude, tone, and frequency of uterine contractions. The primary mechanism involves direct stimulation of alpha-adrenergic receptors and serotonin (5-HT2) receptors on the myometrium. Unlike oxytocin, its effect is not dependent on the gestational age of the uterus and is effective even in the non-pregnant uterus.
3. Indications & Uses
- Prevention and treatment of postpartum hemorrhage (PPH) due to uterine atony.
- Management of subinvolution of the uterus postpartum.
- To aid in the expulsion of retained placental fragments or products of conception.
4. Dosage & Administration
Adult Dosage: **Prevention/Treatment of PPH:** Oral: 0.125 to 0.25 mg (125-250 mcg) three to four times daily for 2-7 days postpartum. IM/IV: 0.2 mg (200 mcg) after delivery of the anterior shoulder, after delivery of the placenta, or during puerperium. May be repeated every 2-4 hours as needed. IV administration should be slow over at least 60 seconds.
Administration: **Oral:** Can be taken with or without food. **Parenteral (IM/IV):** For IV use, administer SLOWLY over no less than 60 seconds with careful monitoring of blood pressure and vital signs. Rapid IV injection can cause severe hypertension, seizures, and stroke. IM route is preferred for routine prophylaxis. Should be administered by healthcare professionals in a setting equipped to manage hypertensive crises.
5. Side Effects
Common side effects may include:
- Nausea
- Vomiting
- Dizziness
- Headache
- Diaphoresis (sweating)
- Tinnitus
- Transient hypertension
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Strong CYP3A4 Inhibitors (e.g., Clarithromycin, Ketoconazole, Ritonavir) | Markedly increased methylergometrine plasma levels, leading to severe toxicity (ergotism, vasospasm, ischemia). | Contraindicated / Major |
| Vasoconstrictors (e.g., Sympathomimetics like Epinephrine, Norepinephrine) | Potentiated hypertensive response, risk of severe hypertension and cerebrovascular events. | Major |
| Other Ergot Alkaloids (e.g., Ergotamine, Dihydroergotamine) | Additive toxic effects, increased risk of vasospasm and ischemia. | Major |
| Protease Inhibitors (HIV therapy) | Increased methylergometrine levels due to CYP3A4 inhibition. | Major |
| Macrolide Antibiotics (except Azithromycin) | Increased methylergometrine levels due to CYP3A4 inhibition. | Major |
| Beta-blockers | May potentiate vasoconstrictive effects, leading to excessive peripheral vasoconstriction. | Moderate |
| Triptans (e.g., Sumatriptan) | Increased risk of vasospastic reactions; avoid within 24 hours of each other. | Major |
7. Patient Counselling
- DO take exactly as prescribed by your doctor, for the duration advised (usually short-term).
- DO inform all your doctors and dentists that you are taking this medicine.
- DO report immediately any chest pain, shortness of breath, severe headache, sudden numbness/weakness (especially on one side), severe leg pain/coldness, or vision changes.
- DONT take with grapefruit juice.
- DONT take any other prescription, over-the-counter medicines, or herbal products without consulting your doctor, especially antibiotics or antifungals.
- DONT use if you are pregnant (except as directed postpartum).
8. Toxicology & Storage
Overdose: Symptoms of ergotism: Severe peripheral vasospasm (cold, numb, painful extremities progressing to cyanosis and gangrene), severe hypertension or hypotension, tachycardia or bradycardia, seizures, confusion, hallucinations, coma, nausea, vomiting, abdominal pain, uterine cramping/rupture, myocardial infarction, stroke.
Storage: Store at room temperature (15-25°C), protected from light and moisture. Keep out of reach of children. Do not use after the expiry date. For injectable forms, use immediately after opening ampoule/vial. Do not freeze.