Misoprostol Therapeutics Revisited
Misoprostol, a prostaglandin E₁ analog, is a racemate of four stereoisomers. On administration it rapidly de-esterifies to its active form, misoprostolic acid. Misoprostolic acid is 85% albumin bound and has a half-life of approximately 30 minutes. It is excreted in urine as inactive metabolites. No significant drug interactions have been reported. Besides its gastrointestinal protective and uterotonic activities, misoprostol regulates various immunologic cascades. It inhibits platelet-activating factor and leukocyte adherence, and modulates adhesion molecule expression. It protects against gut irradiation injury, experimental gastric cancer, enteropathy, and constipation. It improves nutrient absorption in cystic fibrosis. Misoprostol has utility in acetaminophen and ethanol hepatotoxicity, hepatitis, and fibrosis. It is effective in asthmatics and aspirin-sensitive asthmatic and allergic patients. It lowers cholesterol and severity of peripheral vascular diseases, prolongs survival of cardiac and kidney transplantation, synergizes cyclosporine, and protects against cyclosporine-induced renal damage. It works against drug-induced renal damage, interstitial cystitis, lupus nephritis, and hepatorenal syndrome. It is useful in periodontal disease and dental repair. Misoprostol enhances glycosoaminoglycan synthesis in cartilage after injury. It prevents ultraviolet-induced cataracts and reduces intraocular pressure in glaucoma and ocular hypertension. It synergizes antiinflammatory and analgesic effects of diclofenac or colchicine and has been administered to treat trigeminal neuralgic pain. It reduces chemotherapy-induced hair loss and recovery time from burn injury, and is effective in treating sepsis, multiple sclerosis, and pancreatitis.

Inappropriate administration of nonsteroidal antiinflammatory drugs (NSAIDs) and failure to cytoprotect patients at risk of NSAID-induced gastrointestinal damage may account for a significant proportion of patients who develop life-threatening complications during treatment with these drugs. Misoprostol is effective in preventing and treating NSAID-induced gastroduodenal damage. It also has uterotonic activity and can induce labor; hence, it is contraindicated in pregnancy.

In recent years it became apparent that the effectiveness of misoprostol is not limited to protecting the gastroduodenum from NSAIDs and promoting uterotonic activity. The intense therapeutic focus on the former role may have diverted attention away from recognition and development of many other applications of potential clinical importance. Preclinical and clinical studies indicated that the drug may have roles in treating organ systems such as the heart, lungs, kidneys, brain, pancreas, and liver. Therapeutic effects also can be observed in diverse disease states such as allergic disorders, peripheral vascular disease, hyperlipidemia, periodontal disease, osteoporosis, cystic fibrosis, pain, burn injury, and ophthalmologic conditions.