Usage
Misoprostol is a synthetic prostaglandin E1 analog. It is prescribed for the following medical conditions:
- Prevention of NSAID-induced gastric ulcers: It protects the stomach lining from damage caused by nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and aspirin.
- Treatment of duodenal and gastric ulcers: It helps in healing these ulcers even in cases where H2-blocker therapy hasn’t been effective.
- Treatment of erosive gastroduodenitis associated with peptic ulcer disease.
- Prevention of stress-induced upper gastrointestinal mucosal bleeding and lesions in post-surgical adult ICU patients.
- Labor induction (off-label): To ripen the cervix and induce labor.
- Postpartum hemorrhage (off-label): To control bleeding after childbirth.
- Early pregnancy loss (off-label): Medical management of miscarriage, missed abortion, and incomplete abortion.
- Pregnancy termination (off-label): In combination with mifepristone.
Pharmacological Classification: Prostaglandin E1 analog.
Alternate Names
Generic Name: Misoprostol.
Brand Names: Cytotec, Arthrotec (in combination with diclofenac).
How It Works
Pharmacodynamics: Misoprostol binds to prostaglandin E1 receptors on parietal cells in the stomach, decreasing gastric acid secretion. It also increases bicarbonate and mucus production, enhancing mucosal defense. In the uterus, it causes contractions.
Pharmacokinetics:
- Absorption: Rapidly absorbed orally. De-esterified to misoprostol acid, its active form.
- Metabolism: Metabolized in the liver via beta-oxidation and omega-oxidation.
- Elimination: Primarily renal excretion. Short half-life (20-40 minutes).
Mode of Action: Binds to prostaglandin E1 receptors.
Receptor Binding: Prostaglandin E1 receptors.
Dosage
Standard Dosage
Adults:
- NSAID-induced ulcer prophylaxis: 200 mcg orally four times daily with food. May decrease to 100 mcg four times daily if the higher dose is not tolerated. The last dose should be taken at bedtime.
- Gastric and duodenal ulcers: 800 mcg daily in divided doses with meals and at bedtime for 4-8 weeks.
Children: Safety and efficacy not established in children under 8 years old. For cystic fibrosis patients 8 years and older: 100 mcg orally every 6 hours.
Special Cases:
- Elderly Patients: No routine dosage adjustment is recommended. May need to reduce the dose if not tolerated.
- Patients with Renal Impairment: Use with caution. Dosage adjustment is not routinely needed, but it can be reduced if the standard dose isn’t tolerated.
- Patients with Hepatic Dysfunction: No specific dosage adjustment is provided in product labeling.
Clinical Use Cases
Off-label uses; dosages may vary depending on the clinical situation and should be determined by the treating physician.
- Induction of Labor: 25 mcg intravaginally initially, then repeated at intervals not exceeding 3-6 hours. Not to be used in patients with a previous cesarean delivery or major uterine surgery.
- Postpartum Hemorrhage: 600 mcg orally within 1 minute of delivery. Treatment: 800 mcg orally once.
- Early Pregnancy Loss: Varies by type of loss.
- Missed Abortion: 800 mcg intravaginally OR 600 mcg sublingually once. May be repeated every 3 hours for up to two more doses.
Side Effects
Common Side Effects:
Diarrhea, abdominal pain, nausea, headache, menstrual irregularities.
Rare but Serious Side Effects:
Uterine rupture, severe allergic reactions (anaphylaxis).
Adverse Drug Reactions (ADR):
Severe diarrhea, anaphylaxis, uterine hyperstimulation
Contraindications
- Pregnancy (except when used for pregnancy-related conditions under strict medical supervision).
- Known allergy to misoprostol or other prostaglandins.
- Breastfeeding (caution advised).
Drug Interactions
- Antacids containing magnesium: May increase the risk of diarrhea.
- NSAIDs: Misoprostol is often prescribed with NSAIDs to prevent ulcers but may worsen diarrhea.
Pregnancy and Breastfeeding
- Pregnancy: Contraindicated except for specific pregnancy-related uses under the care of a healthcare provider. Can cause birth defects, abortion, premature birth, and uterine rupture. FDA Pregnancy Category X.
- Breastfeeding: Use with caution. Misoprostol is excreted in breast milk in small amounts. Monitor the infant for diarrhea, nausea, vomiting, and poor feeding.
Drug Profile Summary
- Mechanism of Action: Prostaglandin E1 analog; decreases gastric acid secretion, increases mucosal protection; causes uterine contractions.
- Side Effects: Diarrhea, abdominal pain, nausea, headache.
- Contraindications: Pregnancy, allergy to prostaglandins.
- Drug Interactions: Magnesium-containing antacids.
- Pregnancy & Breastfeeding: Contraindicated in pregnancy except for specific conditions; use with caution during breastfeeding.
Popular Combinations
- Mifepristone and Misoprostol: Used for medical abortion.
- Diclofenac and Misoprostol (Arthrotec): Used to treat osteoarthritis pain while protecting against NSAID-induced ulcers.
Precautions
- General Precautions: Use cautiously in patients with renal or hepatic impairment, cardiovascular disease, or diabetes.
- Specific Populations: Avoid in pregnancy unless under strict medical supervision for specific indications; caution in breastfeeding women.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Misoprostol for the prevention of NSAID-induced ulcers?
A: 200 mcg orally four times a day with meals. The last dose should be taken at bedtime. The dose may be reduced to 100 mcg four times daily if the higher dose is not tolerated.
Q2: Can Misoprostol be used during pregnancy?
A: Misoprostol is generally contraindicated during pregnancy due to the risk of birth defects, abortion, premature birth, and uterine rupture. However, it may be used under strict medical supervision for specific pregnancy-related conditions, such as medical abortion, miscarriage management, labor induction and postpartum hemorrhage.
Q3: What are the most common side effects of Misoprostol?
A: The most common side effects are diarrhea, abdominal pain, nausea, and sometimes headache.
Q4: How does Misoprostol work to prevent gastric ulcers?
A: It binds to prostaglandin E1 receptors in the stomach, decreasing gastric acid secretion and increasing protective mucus and bicarbonate production.
Q5: What should patients be advised about while taking Misoprostol?
A: Patients should take Misoprostol with food to reduce the risk of diarrhea. They should also avoid magnesium-containing antacids. Women of childbearing potential should use effective contraception. Patients should inform their doctor of any other medications they are taking.
Q6: Are there any specific precautions for elderly patients taking Misoprostol?
A: While no routine dosage adjustment is recommended, elderly patients may be more susceptible to side effects, particularly diarrhea. Dose reduction may be necessary if the standard dose is not tolerated.
Q7: How should Misoprostol be administered for labor induction?
A: Off-label use. 25 mcg intravaginally initially, then repeated at intervals not to exceed every 3-6 hours. It’s crucial to monitor uterine activity and fetal status closely in a hospital setting. Avoid use in patients with prior cesarean delivery or major uterine surgery.
Q8: What is the role of Misoprostol in the management of postpartum hemorrhage?
A: Off-label use. It can be used to control bleeding after childbirth, typically at a dose of 600-1000 mcg administered orally, sublingually, or rectally.
Q9: How does misoprostol interact with mifepristone?
A: Mifepristone is a progesterone receptor antagonist that sensitizes the uterus to the effects of misoprostol, making the combination more effective for medical abortion and miscarriage management.
Q10: What are the contraindications of misoprostol usage for medical abortion?
A: Contraindications include ectopic pregnancy, molar pregnancy, allergy to either drug, bleeding disorder, concurrent anticoagulant therapy, pelvic infection, hemodynamic instability, and the presence of an intrauterine device. IUD must be removed before treatment.
