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A British pharmaceutical company has asked the Food and Drug Administration to approve the world's first prescription drug developed from key ingredients of marijuana.

GW Pharmaceuticals of Britain has developed a mouth spray called Sativex that contains marijuana's two best known psychoactive ingredients, Delta-9 THC and cannabinoids. The company is in advanced clinical trials to the get the spray approved in the United States as treatment for severe cancer pain.

The drug is already approved in Canada, New Zealand, and eight European countries, including the United Kingdom, Czech Republic, Germany, Spain, Denmark and Sweden for relieving muscle spasms for patients with multiple sclerosis.

The company lists the main effects of cannabinoids as anti-inflammatory, anticonvulsant, antipsycotic, anti-oxidant, neuroprotective, immunomodulatory, and the main effects of THC as analgesic, anti-spasmodic, anti-tremor, anti-inflammatory, appetite stimulant, anti-emetic.

GW Pharmaceuticals said the most common side effects of Sativex are dizziness and fatigue.

Last April, the U.S. Patent and Trademark Office issued a notice of allowance for a patent which protects the use of Sativex as a treatment for cancer pain, providing an exclusivity period until April 2025.

In 1985, the FDA approved Cesamet and Marinol, two drugs that contained synthetic versions of THC to treat chemotherapy side-effects. The FDA eventually approved Marinol's use as an appetite stimulant in AIDS patients as well.

But marijuana use remains illegal under federal law, although 16 states and the District of Columbia have legalized medicinal marijuana in some form.

"There is a real disconnect between what the public seems to be demanding and what the states have pushed for and what the market is providing," said Aron Lichtman, a Virginia Commonwealth University pharmacology professor and president of the International Cannabinoid Research Society, according to The Associated Press. "It seems to me a company with a great deal of vision would say, 'If there is this demand and need, we could develop a drug that will help people and we will make a lot of money.'"

The Department of Justice's Drug Enforcement Administration shot down a petition to reclassify marijuana as a drug with important medicinal properties in July 2011, citing that it has "no accepted medical use."  Marijuana therefore remains within the strictest categorization of restricted substances, alongside heroin and LSD.