Currently, a synthetic version of THC is available to cancer and HIV/AIDS patients in the U.S. as an oral drug known by the brand name Marinol. Approved by the U.S. Food and Drug Administration, the drug (dronabinol) allows patients and doctors to control the amount of active compound that is delivered.
Benson noted, however, that some patients prefer smoking pot to taking pills because the effects set in much faster. "When you inhale something into the lungs, it's very rapidly absorbedyou get an effect in five minutes," he said. "When you take a capsule, it may take an hour and a half."
THC drugs would be more effective, Benson added, if they were delivered through a fast-acting oral spray similar to asthma inhalers.
According to the 1999 IOM report, the legal status of marijuana has greatly colored the scientific debate over the plant's use in medicine.
The broad U.S. federal drug law known as the Controlled Substances Act of 1970 lists marijuana as a Schedule I substance. The designation describes drugs with a high potential for abuse and no accepted medical use. Other Schedule I drugs include heroin and LSD.
In 1972 the National Organization for the Reform of Marijuana Legislation, a nonprofit advocacy group, unsuccessfully lobbied the U.S. government to relist marijuana as a Schedule II substance. That class includes drugs such as morphine and cocaine that are highly addictive but have well-established medical uses.
Based on the IOM study, the U.S. Drug Enforcement Administration (DEA) maintains that smoked marijuana should remain a Schedule I drug. Any medical effects from smoking marijuana cigarettes can be met more effectively with approved commercial drugs, the agency says.
In fact, DEA has placed the THC drug Marinol in Schedule IIIa less restrictive categoryand supports research to find new delivery methods and therapeutic uses for cannabinoids.
Pertwee, of the University of Aberdeen, believes the potential for patients to become addicted to manufactured cannabinoid drugs is relatively low. However, conflicting data exist as to whether long-term THC use leads to dependency.
Benson also believes that medical marijuana, even when smoked by terminal patients, is unlikely to trigger addiction if use remains carefully monitored. "If you have a controlled distribution system for medical use, as with morphine, for example, I don't see the risk," he said.
On June 6 the U.S. Supreme Court declared that federal drug law overrides policies in ten states that allow marijuana for medical use. The ruling upholds the federal government's right to destroy homegrown plants and to arrest anyone possessing the drug, even if they are using it following a doctor's advice.
California passed the first medical marijuana law in 1996. Between 1999 and 2004, nine more states followed suit. Police in these states allow local doctors to recommend that special medical-marijuana-use licenses be issued to needy patients.
The Supreme Court's decision doesn't overturn the states' liberalized stance. But Benson believes it will affect the drug's accessibility.
"I think this ruling is going to inhibit physicians from recommending [marijuana]," he said, noting worries by some that the government could revoke doctors' licenses to prescribe other controlled substances. "But it will remain a drug purchased on the street, grown in cellars and backyards."
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