Misoprostol is a synthetic prostaglandin medication used to prevent and treat stomach and duodenal ulcers, induce labor, cause an abortion, and treat postpartum bleeding due to poor contraction of the uterus. It is taken by mouth when used to prevent gastric ulcers in people taking nonsteroidal anti-inflammatory drugs (NSAID). For abortions it is typically used in conjunction with mifepristone or methotrexate, but can be used alone. By itself, effectiveness for abortion is between 82% and 100%. Its efficacy with mifepristone is higher, but varies based on gestational age. The misoprostol-only abortion regimen is typically recommended only when mifepristone is not available. For labor induction or abortion, it is taken by mouth, dissolved in the mouth, or placed in the vagina. For postpartum bleeding it may also be used rectally. Common side effects include diarrhea and abdominal pain. It is in pregnancy category X, meaning that it is known to result in negative outcomes for the fetus if taken during pregnancy. In rare cases, uterine rupture may occur. It is a prostaglandin analogue—specifically, a synthetic prostaglandin E1 (PGE1). Misoprostol was developed in 1973 and first created for the treatment of gastric ulcers. Its first uses for abortion emerged in Latin America in the 1980s, as women noticed miscarriage was a side effect of the medication. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication.
Medical uses
Ulcer prevention Misoprostol is used for the prevention of NSAID-induced gastric ulcers. It acts upon gastric parietal cells, inhibiting the secretion of gastric acid by G-protein coupled receptor-mediated inhibition of adenylate cyclase, which leads to decreased intracellular cyclic AMP levels and decreased proton pump activity at the apical surface of the parietal cell. Misoprostol is sometimes coprescribed with NSAIDs to prevent their common adverse effect of gastric ulceration (e.g., with diclofenac in Arthrotec). However, even in the treatment of NSAID-induced ulcers, omeprazole proved to be at least as effective as misoprostol, but was significantly better tolerated, so misoprostol is not considered a first-line treatment. Misoprostol-induced diarrhea and the need for multiple daily doses impairing treatment for gastric ulcers.
Labor induction Misoprostol is commonly used for labor induction. It causes uterine contractions and the ripening (effacement or thinning) of the cervix. It can be less expensive than the other commonly used ripening agent, dinoprostone. Oxytocin has long been used as the standard agent for labor induction, but does not work well when the cervix is not yet ripe. Misoprostol also may be used in conjunction with oxytocin. Between 2002 and 2012, a misoprostol vaginal insert was studied, and was approved in the EU. It was not approved for use in the United States, and the US FDA still considers cervical ripening and labor induction to be outside of the approved uses for misoprostol. The vaginal and oral routes of misoprostol for labor induction are comparably effective, and are considered on a case-by-case basis by healthcare professionals.
Myomectomy When administered prior to myomectomy in women with uterine fibroids, misoprostol reduces operative blood loss, requirement of blood transfusion, and operating time.
Abortion Misoprostol is used either alone or in conjunction with another medication (mifepristone or methotrexate) for medical abortions as an alternative to surgical abortion. Misoprostol alone is typically only recommended when another medication is not available and is more effective when paired with mifepristone or methotrexate. Medical abortion has the advantage of being less invasive, and more autonomous, self-directed, and discreet. It is preferred by some women because it feels more natural, as the drugs induce a miscarriage. It is also more easily accessible in places where abortion is illegal. The World Health Organization (WHO) provides clear guidelines on the use, benefits and risks of misoprostol for abortions. Misoprostol is most effective when it is used in combination with methotrexate or mifepristone (RU-486). Mifepristone blocks signaling by progesterone, causing the uterine lining to degrade, the blood vessels of the cervix and uterus to dilate and causing uterine contraction, similar to a menstrual period, which causes the embryo to detach from the uterine walls. Misoprostol then dilates the cervix and induces muscle contractions which clear the uterus. Misoprostol alone is less effective (typically 88% up to eight-weeks gestation). It is not inherently unsafe if medically supervised, but 1% of women will have heavy bleeding requiring medical attention, some women may have ectopic pregnancy, and the 12% of pregnancies that continue after misoprostol failure are more likely to have birth defects and are usually followed up with surgical intervention. Most large studies recommend a protocol for the use of misoprostol in combination with mifepristone. Together they are effective in around 95% for early pregnancies. Misoprostol alone may be more effective in earlier gestation. Misoprostol can also be used to dilate the cervix in preparation for a first-trimester surgical abortion (either alone or in combination with osmotic dilators), but is not routinely recommended. Misoprostol by mouth is the least effective treatment for producing complete abortion in a period of 24 hours due to the liver's first-pass effect which reduces the bioavailability of the misoprostol. Vaginal and sublingual routes result in greater efficacy and extended duration of action because these routes of administration allow the drug to be directly absorbed into circulation by bypassing the liver first-pass effect. Hematocrit or Hb tests and Rh testing are recommended before use for abortion confirmation of pregnancy. Following use, it is recommended that people attend a follow-up visit 2 weeks after treatment. If used for treatment of complete abortion, a pregnancy test, physical examination of the uterus, and ultrasound should be performed to ensure success of treatment. Surgical management is possible in the case of failed treatment.
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