Misoprostol; Uses, Side Effects, Drug Interactions, Pregnancy

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Misoprostol is a synthetic analog of natural prostaglandin E1. It produces a dose-related inhibition of gastric acid and pepsin secretion and enhances mucosal resistance to injury. It is an effective anti-ulcer agent and also has oxytocic properties.
Misoprostol is only found in individuals that have used or taken this drug. It is a synthetic analog of natural prostaglandin E1. It produces a dose-related inhibition of gastric acid and pepsin secretion and enhances mucosal resistance to injury. It is an effective anti-ulcer agent and also has oxytocic properties. [PubChem]Misoprostol seems to inhibit gastric acid secretion by a direct action on the parietal cells through binding to the prostaglandin receptor. The activity of this receptor is mediated by G proteins which normally activate adenylate cyclase. The indirect inhibition of adenylate cyclase by Misoprostol may be dependent on guanosine-5& rsquo; -triphosphate (GTP). The significant cytoprotective actions of misoprostol are related to several mechanisms. These include 1. Increased secretion of bicarbonate, 2. The considerable decrease in the volume and pepsin content of the gastric secretions, 3.

Misoprostol is a medication used to start labor, cause an abortion, prevent and treat stomach ulcers, and treat postpartum bleeding due to poor contraction of the uterus. For abortions, it is often used with mifepristone or methotrexate. By itself, effectiveness for this purpose is between 66% and 90%. It is taken either in the cheek, under the tongue, or placed in the vagina. A synthetic analog of natural prostaglandin E1. It produces a dose-related inhibition of gastric acid and pepsin secretion and enhances mucosal resistance to injury. It is an effective anti-ulcer agent and also has oxytocic properties.

Mechanism of Action of Misoprostol

Misoprostol seems to inhibit gastric acid secretion by a direct action on the parietal cells through binding to the prostaglandin receptor. The activity of this receptor is mediated by G proteins which normally activate adenylate cyclase. The indirect inhibition of adenylate cyclase by Misoprostol may be dependent on guanosine-5’-triphosphate (GTP). The significant cytoprotective actions of misoprostol are related to several mechanisms. These include 1. Increased secretion of bicarbonate, 2. The considerable decrease in the volume and pepsin content of the gastric secretions, 3. It prevents harmful agents from disrupting the tight junctions between the epithelial cells which stops the subsequent back diffusion of H+ ions into the gastric mucosa, 4. The increased thickness of the mucus layer, 5. Enhanced mucosal blood flow as a result of direct vasodilatation, 6. Stabilization of tissue lysozymes/vascular endothelium, 7. Improvement of mucosal regeneration capacity, and 8. Replacement of prostaglandins that have been depleted as a result of various insults to the area. Misoprostol has also been shown to increase the amplitude and frequency of uterine contractions during pregnancy via selective binding to the EP-2/EP-3 prostanoid receptors.

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Indications of Misoprostol

  • Abortion
  • Cervical ripening
  • Gynecological conditions
  • Duodenal ulcer
  • Labor induction
  • NSAID-induced ulcer prophylaxis
  • Postpartum bleeding
  • Stomach ulcer
  • Gastric ulcer
  • Incomplete abortion
  • Missed abortion
  • Postpartum hemorrhage

Indicated for the treatment of ulceration (duodenal, gastric and NSAID induced) and prophylaxis for NSAID induced ulceration. Misoprostol is also indicated for other uses that are not approved in Canada, including the medical termination of an intrauterine pregnancy used alone or in combination with methotrexate, as well as the induction of labor in a selected population of pregnant women with unfavorable cervices. This indication is avoided in women with prior uterine surgery or cesarean surgery due to an increased risk of possible uterine rupture. Misoprostol is also used for the prevention or treatment of serious postpartum hemorrhage.

Contra-Indications of Misoprostol

  • Extreme Loss of body water
  • Inflammatory bowel disease
  • Tearing of the uterus while pregnant
  • Operation of the uterus or the cervix
  • Pregnancy
  • Previous C Section

Dosage of Misoprostol

Strengths: 100 mcg; 200 mcg; 600mcg

Duodenal Ulcer

  • 200 mcg orally 4 times a day after meals and at bedtime
  • Maintenance dose: 100 to 200 mcg orally 4 times a day

Gastric Ulcer

  • 200 mcg orally 4 times a day after meals and at bedtime
  • Maintenance dose: 100 to 200 mcg orally 4 times a day

NSAID-Induced Ulcer Prophylaxis

  • 200 mcg orally 4 times a day after meals and at bedtime
  • Maintenance dose: 100 to 200 mcg orally 4 times a day

Labor Induction

American College of Obstetricians and Gynecologists (ACOG) Recommendations

  • 25 mcg vaginally every 3 to 6 hours
  • Some patients may require doses of 50 mcg every 6 hours

Postpartum Bleeding

ACOG Recommendations

  • 800 to 1000 mcg rectally once

International Federation of Gynecology Obstetrics (FIGO) Recommendations

  • 600 mcg orally OR 800 mcg sublingually once immediately after delivery

Abortion

ACOG Recommendations>First Trimester of Pregnancy

  • Early Pregnancy Loss: 800 mcg intravaginally once; a second dose may be given if there is no response to the first dose no sooner than 3 hours after the first dose, and usually within 7 days
  • Incomplete Abortion: 600 mcg orally once
  • Missed Abortion: 800 mcg intravaginally OR 600 mcg sublingually once; the dose may be repeated every 3 hours for 2 additional doses
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Side Effects of Misoprostol

The most common

More common

Less common

Drug Interactions of Misoprostol

Misoprostol may interact with following drugs, supplements & may decrease the efficacy of drugs

  • crofelemer
  • eluxadoline
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Pregnancy & Lactation

  • FDA PregnancyCategory X

Pregnancy

  • Women who may become pregnant should use adequate birth control (e.g., birth control pills, condoms, or intrauterine devices) while taking misoprostol. Since misoprostol increases the risk of miscarriage, a woman who may be pregnant should not start taking misoprostol until she is sure that she is not pregnant. If you suspect you are pregnant, stop the medication and contact your doctor.

Lactation

  • Breast-feeding mothers should not take misoprostol, as it may cause significant diarrhea for breast-feeding infants. The safety and effectiveness of this medication have not been established for children and adolescents under 18 years of age.

References