Misoprostol (Molecule of the Month for April 2008)
Misoprostol is a drug that is FDA-approved in the United States for the prevention of NSAID-induced gastric ulcers. It is also used (and approved in other countries) to induce labor and as an abortifacient. It was invented and marketed by G.D. Searle & Company (now Pfizer) under the trade name Cytotec. Misoprostol stimulates increased secretion of the protective mucus that lines the gastrointestinal tract and increases mucosal blood flow, thereby increasing mucosal integrity. It is sometimes co-prescribed with non-steroidal anti-inflammatory drugs to prevent their common adverse effect of gastric ulceration (e.g. with Diclofenac in Arthrotec).
Misoprostol is commonly prescribed off-label to cause labor induction by promoting uterine contractions and the ripening (effacement or thinning) of the cervix. Misoprostol is considered to be more effective than oxytocin and dinoprostone, the FDA-approved drugs for medically necessary labor induction. It is also less expensive than either of these two drugs. Concern has been expressed about the overuse or misuse of misoprostol for labor induction. High doses can cause uterine rupture (especially in women who have previously had a caesarean section), fetal death, and severe fetal brain damage. All induction agents cause uterine contractions – this can affect the blood supply to the fetus, especially if contractions become very frequent. Induction agents therefore need to be used with great care and with close fetal monitoring. One of the problems with induction using prostaglandins (such as dinoprostone or misoprostol) is that once given, the process is difficult to reverse. In contrast, oxytocin has a half-life of about 10 minutes and is administered via intravenous drip, which can be stopped immediately in the event of adverse reaction.
Misoprostol is one of the drugs used for medical abortions in lieu of surgical evacuation. Both medical and surgical methods can be used to removed products of conception in the case of missed or incomplete miscarriage, retained postpartum placenta, and for elective abortion. There are some advantages to using drugs instead of surgical intervention in these situations, as drugs are not invasive, reducing the risk from general anesthesia, infection as well as secondary infertility due to scarring and intrauterine adhesions (Asherman's Syndrome). Furthermore it is cheap and easy to administer. In many countries it is used in conjunction with mifepristone (RU-486). After mifepristone is taken orally, misoprostol is taken 24–72 hours later causing the expulsion of the fetus and associated matter in approximately 92% of the cases. No large studies have established a protocol for the use of misoprostol alone, and the range of efficacy is 65%–93% depending on sample size, gestational age, and other test variables. Misoprostol alone may be more effective in earlier gestation. The side effects associated with the misoprostol-only regimen are generally much more severe than those associated with the combined regimens. Misoprostol is used for self-induced abortions in Brazil, where black market prices exceed US $100 per dose. Illegal medically-unsupervised misoprostol abortions in Brazil are associated with a lower complication rate than other forms of illegal self-induced abortion, but are still associated with a higher complication rate than legal, medically supervised surgical and chemical abortions. Failed misoprostol abortions are associated with birth defects in some cases. Poor immigrant populations in New York have also been observed to use self-administered misoprostol to induce abortions, as this method is much cheaper than a surgical abortion (about $2 per dose).
Formal Chemical Name (IUPAC)
Update by Karl Harrison
(Molecule of the Month for April 2008 )