Although marijuana (cannabis) has been used in medicine for thousands of years, its place as a drug in modern medicine has been the subject of intense debate. Among the earliest Western medical reports was one written in 1839 by William O’Shaughnessy, an Irish physician working in India. He noted that cannabis was nontoxic in animals and that it suppressed convulsions and relieved muscle spasms and pain in his patients. In 1912, the author of a leading textbook of therapeutics spoke with praise about cannabis’s value in relieving cough, pain, menstrual cramps, and the tremors of Parkinson’s disease, and in preventing migraine headaches. Other authors extolled its virtues for curbing the withdrawal symptoms of alcohol and heroin addiction. Over the years, however, more effective drugs became available for these purposes, and cannabis lost favor in the medical community.
In recent decades, marijuana has been the subject of renewed medical interest because of its very low toxicity. Among its most promising potential uses is relief of severe, debilitating nausea and vomiting caused by anticancer drugs, when other antiemetic drugs prove ineffective. It also stimulates appetite in AIDS patients who have experienced extreme weight loss. Other medical applications may include reduction in the eye-fluid pressure of glaucoma patients, relief of spasticity in patients with multiple sclerosis or spinal cord injuries, and suppression of pain that fails to respond to other drugs. Dronabinol (Marinol), a synthetic THC, and nabilone (Cesamet), a THC derivative, are available in several countries as orally active substitutes for cannabis, which is smoked and medically discouraged.
The recreational use of marijuana is illegal in most nations, but its medical use is legal in some countries. The Food and Drug Administration has not approved of the use of marijuana for medical purposes, although it is available for such use in approximately one-third of the United States. A conflict exists in the United States between the federal law making the possession of cannabis illegal and creating major impediments to testing its medical effectiveness, and state laws, which permi1t its use for selected medical conditions.