Today, in the United States, such use is prohibited. Although thirty-six states have passed legislation to allow marijuana's use as a medicine, federal law preempts their making marijuana legally available to patients.
A number of studies have shown that marijuana is effective in reducing nausea and vomiting, lowering intraocular pressure associated with glaucoma, and decreasing muscle spasm and spasticity. Today, many people use marijuana for these and other medical purposes, despite its illegal status.
People undergoing cancer chemotherapy have found smoked marijuana to be an effective anti-nauseant often more effective than available pharmaceutical medications. Indeed, 44 percent of oncologists responding to a questionnaire said they had recommended marijuana to their cancer patients; others said they would recommend it if it were legal.
Marijuana is also smoked by thousands of AIDS patients to treat the nausea and vomiting associated with both the disease and AZT drug therapy. Because it stimulates appetite, marijuana also counters HIV-related "wasting," allowing AIDS patients to gain weight and prolong their lives.
In 1986, a synthetic delta-9-THC capsule (Marinol) was marketed in the United States and labeled for use as an anti-emetic. Despite some utility, this product has serious drawbacks, including its cost. For example, a patient taking three 5 mgm capsules a day would spend over $5,000 to use Marinol for one year. In comparison to the natural, smokeable product Marinol also has some pharmacological shortcomings. Because THC delivered in oral capsules enters the bloodstream slowly, it yields lower serum concentrations per dose. Oral THC circulates in the body longer at effective concentrations, and more of it is metabolized to an active compound; thus, it more frequently yields unpleasant psychoactive effects. In patients suffering from nausea, the swallowing of capsules may itself provoke vomiting. In short, the smoking of crude marijuana is more efficient in delivering THC and, in some cases, it may be more effective.
The continuing illegality of medical marijuana is based more on political than scientific considerations. Although during the 1970s the government supported exploration into marijuana's therapeutic potential, its role has become one of blocking new research and opposing any change in marijuana's legal status.
From http://www.drugtext.org/articles/marijuan.htm Zimmer & Morgan on Myths.