New Studies Destroy the Last Objection to Medical Marijuana

Anyone who advocates for medical marijuana sooner or later runs into arguments about smoking: "No real medicine is smoked." "Smoking is bad for the lungs; why would any doctor recommend something so harmful?" It's a line of reasoning that medical marijuana opponents have used to great effect in Congress, state legislatures, and elsewhere. Indeed, the FDA's controversial 2006 statement opposing medical marijuana was couched in repeated references to "smoked marijuana."

But new research demonstrates that all those fears of "smoked marijuana" as medicine are 100 percent obsolete.

The smoking argument was the closest thing to a scientifically meaningful objection to medical marijuana. While marijuana smoke, unlike tobacco, has never been shown to cause lung cancer, heavy marijuana smoking has been associated with assorted respiratory symptoms and a potentially increased risk of bronchitis. That's because burning any plant material produces a whole lot of substances such as tars, and carbon monoxide that are not good for the lungs.

Nevertheless, inhalation is clearly the best method for administering marijuana's active components, called cannabinoids. Cannabinoids such as THC are fat-soluble molecules that are absorbed slowly and unevenly when taken orally, as in the prescription THC pill Marinol. This means that Marinol typically takes an hour to two hours to work, and dose adjustment is nearly impossible. Patients often report that when it finally kicks in, it hits like a ton of bricks, leaving them too stoned to function.

For that reason, The Lancet Neurology noted a few years ago, "Smoking has been the route of choice for many cannabis users because it delivers a more rapid 'hit' and allows more accurate dose titration." Because the effect is nearly instantaneous, patients can simply take as many puffs as they need, stopping when they've achieved the needed effect without excessive intoxication.

So far, no pharmaceutical product -- not even Sativex, the much-touted marijuana spray now marketed in Canada -- achieves this combination of rapid action and simple, accurate dose adjustment.

Back in 1999, the Institute of Medicine's White House-commissioned report on medical marijuana conceded marijuana's medical benefits, saying that what is needed is "a nonsmoked rapid-onset cannabinoid drug delivery system."

The new studies -- one from the University of California, San Francisco, and the other from the University at Albany, State University of New York -- confirm that such a system is here. It's called vaporization, and has been familiar to medical marijuana patients for many years, but few outside the medical marijuana community know it exists. Unlike smoking, a vaporizer does not burn the plant material, but heats it just to the point at which the THC and the other cannabinoids vaporize. In the Volcano vaporizer tested at UCSF, the vapors are collected in a detachable plastic bag with a mouthpiece for inhalation.

The UCSF study, conducted by Dr. Donald Abrams and colleagues and just published online by the journal Clinical Pharmacology and Therapeutics (to appear in the journal's print edition on May) compared a commercially available vaporizer called the Volcano to smoking in 18 volunteers. The subjects inhaled three different strengths of marijuana either as smoked cigarettes or vaporized using the Volcano.

The researchers then measured the volunteers' plasma THC levels and the amount of expired carbon monoxide, which is considered a reliable marker for the unwanted combustion products contained in smoke.

The two methods produced similar THC levels, with vaporization producing somewhat higher levels, and were judged equally efficient for administration of cannabinoids. The big difference was in expired carbon monoxide. As expected, there was a sharp increase in carbon monoxide levels after smoking, while "little if any" increase was detected after vaporization. "This indicates little or no exposure to gaseous combustion toxins," the researchers wrote. "Vaporization of marijuana does not result in exposure to combustion gases, and therefore is expected to be much safer than smoking marijuana cigarettes."