1. Clinical Overview
Misoprostol is a synthetic prostaglandin E1 (PGE1) analogue. It is a potent gastric antisecretory and mucosal protective agent, but its primary clinical use in India is for its uterotonic effects, specifically for medical termination of pregnancy (MTP) and for the prevention and treatment of postpartum hemorrhage (PPH). It is also used for cervical ripening prior to surgical procedures and for the management of missed or incomplete miscarriage. It is not approved for gastric ulcer prophylaxis in India due to its abortifacient potential.
| Onset | Duration | Bioavailability |
|---|---|---|
| Uterine contractions begin within 2-5 minutes of vaginal administration and within 15-30 minutes of oral/sublingual administration. | Uterotonic effects last for approximately 2-3 hours. The plasma concentration declines rapidly, but clinical effects (like cervical ripening) can persist. | Oral: ~80-90% (but undergoes rapid first-pass metabolism). Sublingual: High. Vaginal: Variable but prolonged absorption. |
2. Mechanism of Action
Misoprostol binds to specific prostaglandin EP2/EP3 receptors on smooth muscle cells. In obstetrics/gynecology, it increases the frequency and amplitude of uterine contractions and promotes cervical softening and dilation by stimulating collagen breakdown and increasing glycosaminoglycan content. For gastric protection, it inhibits gastric acid secretion (direct action on parietal cells) and enhances mucosal defense by increasing bicarbonate and mucus secretion while maintaining mucosal blood flow.
3. Indications & Uses
- Medical Termination of Pregnancy (MTP) up to 9 weeks (in combination with Mifepristone)
- Prevention and Treatment of Postpartum Hemorrhage (PPH)
- Cervical ripening prior to surgical termination of pregnancy or other gynecological procedures
- Management of missed or incomplete miscarriage
4. Dosage & Administration
Adult Dosage: **MTP (with Mifepristone):** 800 mcg (4 tablets of 200 mcg) vaginally or sublingually/buccally, 36-48 hours after 200 mg oral Mifepristone. **PPH Prevention:** 600 mcg orally immediately after delivery. **PPH Treatment:** 800-1000 mcg sublingually/rectally. **Cervical Ripening:** 400 mcg vaginally or sublingually, 3-4 hours prior to procedure. **Missed/Incomplete Miscarriage:** 800 mcg vaginally or sublingually (single dose).
Administration: **Oral:** Swallow tablet with water. **Sublingual:** Place tablet under tongue and allow to dissolve completely (15-30 mins). Do not eat or drink during this time. **Vaginal:** Insert tablet high into posterior fornix. Patient should remain recumbent for 30 minutes. **Rectal:** Can be inserted for PPH treatment if oral/sublingual not feasible. Tablets should not be crushed or chewed for oral use (causes increased GI side effects).
5. Side Effects
Common side effects may include:
- Abdominal pain/cramping (dose-related)
- Diarrhea (dose-related)
- Nausea
- Flatulence
- Headache
- Dizziness
- Vaginal bleeding/spotting
- Chills, mild fever (due to prostaglandin effect)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Magnesium-containing Antacids | Increase incidence of diarrhea caused by Misoprostol. | Moderate |
| Oxytocin | Concomitant use can potentiate uterotonic effect, increasing risk of uterine hyperstimulation or rupture. Administer with a time interval (6-8 hours). | Major |
| Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) e.g., Aspirin, Ibuprofen, Diclofenac | May attenuate the uterotonic effect of Misoprostol. Theoretical reduction in efficacy for cervical ripening/abortion. | Moderate |
| Corticosteroids | May potentiate the convulsant effect of misoprostol-induced fever. | Moderate |
| Food | High-fat meal can reduce peak plasma concentration of misoprostol acid but increase bioavailability. Clinical significance is minimal. | Minor |
7. Patient Counselling
- **DO** follow the exact route (vaginal, sublingual, oral) and timing as instructed by your doctor.
- **DO** expect vaginal bleeding and cramping heavier than a menstrual period after use for MTP/miscarriage.
- **DO** return for a follow-up visit 10-14 days after treatment to confirm complete abortion.
- **DO** use effective contraception immediately after a medical abortion, as ovulation can return within 10 days.
- **DON'T** use if you are pregnant and wish to continue the pregnancy.
- **DON'T** share this medicine with anyone else.
- **DON'T** take more tablets than prescribed.
8. Toxicology & Storage
Overdose: Symptoms are extensions of its pharmacological effects: severe diarrhea, abdominal pain/cramping, profound hypotension or hypertension, tachycardia, bradycardia, fever, chills, convulsions, bronchospasm, and uterine hyperstimulation with potential rupture.
Storage: Store at or below 25°C (77°F). Protect from moisture and light. Keep in the original blister pack until use. Keep out of reach of children and sight of others to prevent misuse. Do not flush unused medication. Dispose of as per local biomedical waste guidelines or return to pharmacy.