Short note on Misoprost and Dinoproston and carbaprost like I'm writing for my Final Year MBBS OBGY University exam.
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I now have comprehensive content from multiple authoritative textbooks. Let me compile the exam-style short notes.
Short Notes: Prostaglandin Analogs in Obstetrics & Gynaecology
For Final Year MBBS OBGyn University Exam
1. MISOPROSTOL (Cytotec)
Class: Synthetic PGE₁ analogue (15-methyl analogue of PGE₁)
Mechanism of Action:
- Binds prostaglandin receptors on uterine smooth muscle → stimulates uterine contractions
- Relaxes and softens cervix (collagenase effect on cervical stroma)
- Also acts on parietal cell PG receptors → ↓ gastric acid secretion + ↑ mucus/bicarbonate (cytoprotection)
Routes of Administration: Oral, sublingual, buccal, vaginal, rectal
Advantages over other prostaglandins:
- Inexpensive
- Stable at room temperature (no cold chain required — important in developing countries)
- Multiple routes of administration
- Fewer systemic side effects at obstetric doses
OBGyn Uses:
| Indication | Dose/Route |
|---|---|
| Cervical ripening / Induction of labor | 25 mcg vaginally q 3–6 hrs |
| Medical abortion (with mifepristone) | 800 mcg vaginally or 400 mcg buccal q 3 hrs |
| Postpartum hemorrhage (PPH) prophylaxis | 600 mcg orally or 800–1000 mcg rectally |
| PPH treatment (refractory) | 800–1000 mcg rectally or sublingually |
| Management of missed/incomplete abortion | 800 mcg vaginally |
| Mid-trimester abortion | 400 mcg vaginally q 3–6 hrs |
Adverse Effects:
- Diarrhea, abdominal cramps (most common)
- Nausea, vomiting
- Uterine tachysystole / hyperstimulation → fetal distress
- Pyrexia (less than dinoprostone)
Contraindications:
- Previous uterine scar (relative CI for induction — risk of uterine rupture)
- Prior classical cesarean section
- Hypersensitivity to prostaglandins
Exam Point: Misoprostol is NOT FDA-approved for obstetric indications but is widely used off-label. Recognized by WHO as an essential medicine for PPH prevention.
2. DINOPROSTONE (PGE₂ — Cervidil, Prepidil)
Class: Synthetic PGE₂ analogue
Mechanism of Action:
- Binds EP receptors → stimulates uterine smooth muscle contractions throughout pregnancy
- Directly acts on cervical collagenase → cervical softening, effacement, and dilation (cervical ripening)
- Effect potentiated by oxytocin as pregnancy progresses
- Metabolized locally and on first pass through lungs (~95%); plasma half-life = 2.5–5 minutes; metabolites excreted in urine
Preparations & Dosing:
| Preparation | Trade Name | Route | Dose |
|---|---|---|---|
| Vaginal gel | Prepidil | Intracervical | 0.5 mg q 6 hrs; max 1.5 mg/24 hrs |
| Controlled-release vaginal insert | Cervidil | Intravaginal | 10 mg over 12 hrs (removable) |
| Vaginal suppository | — | Intravaginal | 20 mg q 3–5 hrs (for abortion) |
OBGyn Uses:
- Cervical ripening for induction of labor at or near term
- Induction of labor (when cervix unfavorable)
- Second-trimester abortion (20 mg vaginal suppository)
- Missed abortion / intrauterine fetal death
- Benign hydatidiform mole evacuation
Advantages of Cervidil insert:
- Removable in case of uterine hyperstimulation
- Lower GI side effects (<1% vs 5.7% with gel)
Adverse Effects:
- Fever (characteristic — more than misoprostol)
- Nausea, vomiting, diarrhea
- Uterine hyperstimulation
- Headache, chills
Contraindications:
- Previous cesarean or uterine scar
- Asthma, glaucoma, myocardial infarction (caution)
- Non-reassuring fetal status
- Active genital herpes
- Hypersensitivity to prostaglandins
Exam Point: Dinoprostone is the only prostaglandin FDA-approved for cervical ripening. The controlled-release insert (Cervidil) can be removed if hyperstimulation occurs — this is its key clinical advantage.
3. CARBOPROST (Hemabate)
Class: 15-methyl analogue of PGF₂α (Carboprost tromethamine)
The 15-methyl group prolongs duration of action compared to natural PGF₂α.
Mechanism of Action:
- Stimulates uterine smooth muscle contractions (powerful oxytocic)
- Causes bronchoconstriction (PGF₂α effect on bronchial smooth muscle)
- Strong GI smooth muscle stimulation
Route & Dose:
- IM injection: 250 mcg (0.25 mg)
- Repeated every 15–90 minutes as needed
- Maximum total dose: 2 mg (8 doses)
OBGyn Uses:
- Postpartum hemorrhage (refractory uterine atony) — primary OBGyn indication; used when oxytocin fails; success rate ~80%
- Second-trimester abortion induction
- Mid-trimester pregnancy termination
Step in PPH management: Carboprost is a second-line uterotonic (after oxytocin ± ergometrine) in the "MACE" mnemonic:
- M — Methylergonovine
- A — (after oxytocin)
- C — Carboprost
- E — —
Adverse Effects:
- Diarrhea and vomiting (very common — GI smooth muscle stimulation)
- Bronchoconstriction (important!)
- Transient fever (in ~1/8 patients)
- Flushing, headache
Contraindications:
- Asthma (absolute — causes bronchoconstriction)
- Cardiovascular disease (use with great caution)
- Active cardiac, pulmonary, renal, or hepatic disease
Exam Point: Carboprost is contraindicated in asthma — this is the most tested fact. Use misoprostol (rectal) instead in asthmatics with refractory PPH.
Comparative Summary Table
| Feature | Misoprostol | Dinoprostone | Carboprost |
|---|---|---|---|
| Class | PGE₁ analogue | PGE₂ analogue | PGF₂α analogue |
| Trade name | Cytotec | Cervidil / Prepidil | Hemabate |
| Route | Oral/vaginal/rectal/buccal | Vaginal/intracervical | IM only |
| Storage | Room temperature ✓ | Refrigeration needed | Refrigeration needed |
| Key OBGyn use | PPH, abortion, induction | Cervical ripening, abortion | Refractory PPH, abortion |
| Characteristic SE | Diarrhea, hyperstimulation | Fever | Bronchoconstriction, diarrhea |
| CI in asthma | No | Caution | Yes — absolute CI |
| FDA-approved for induction | Off-label | Yes (Cervidil) | No |
| Cost | Cheapest | Expensive | Expensive |
High-Yield Exam Points
- Misoprostol = PGE₁; cheapest, heat-stable, multipurpose; used for PPH, induction, abortion; off-label for obstetrics but WHO-recommended.
- Dinoprostone = PGE₂; only FDA-approved cervical ripening agent; Cervidil (insert) is removable — key safety advantage.
- Carboprost = 15-methyl PGF₂α; contraindicated in asthma; used for refractory PPH when oxytocin fails; IM 250 mcg, max 8 doses.
- All three cause uterine hyperstimulation — monitor for fetal distress.
- Dinoprostone is most associated with fever; carboprost with bronchoconstriction; misoprostol with diarrhea.
- In resource-limited settings: misoprostol is the preferred uterotonic because no cold chain required.
Sources: Lippincott Illustrated Reviews: Pharmacology; Katzung's Basic and Clinical Pharmacology, 16th Ed.; Creasy & Resnik's Maternal-Fetal Medicine; Berek & Novak's Gynecology
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