Posted Thursday, May 28, 2009, at 9:51 AM
Lots of readers responded to yesterday's piece on the transformation of marijuana . I had focused on the drug's evolution from an herb to a powder , a capsule , and finally a spray . But Bruce Mirken of the Marijuana Policy Project says the spray has already been eclipsed by a better way to filter and deliver the drug's therapeutic benefits: vaporization.
Mirken points to several recent studies exploring the vapor method. First, a 2006 article from the Journal of Pharmaceutical Sciences :
What is currently needed for optimal use of medicinal cannabinoids is a feasible, nonsmoked, rapid-onset delivery system. Cannabis "vaporization" is a technique aimed at suppressing irritating respiratory toxins by heating cannabis to a temperature where active cannabinoid vapors form, but below the point of combustion where smoke and associated toxins are produced.
Second, a 2007 report in Clinical Pharmacology & Therapeutics
on the absorption of THC from marijuana inhaled via the Volcanos vaporizer system compared to smoking marijuana cigarettes. We found that THC levels were generally similar over 6 h for the two types of delivery. The vaporizer was associated with higher plasma THC concentrations at 30 min and 1 h compared to smoking at each THC strength, suggesting that absorption was faster with the vaporizer.
Absorption rate is important because it helps you control the drug's effects. The more quickly you feel the effects of an initial dose, the more quickly and accurately you can figure out whether you need more to get the requisite pain relief and, if so, how much. Otherwise, you might overdose before you realize it (although, even in that event, a THC overdose isn't that bad ).
The 2007 paper continues:
Whereas smoking marijuana increased CO [carbon monoxide] levels as expected for inhalation of a combustion product, there was little if any increase in CO after inhalation of THC from the vaporizer. This indicates little or no exposure to gaseous combustion toxins. Combustion products are harmful to health and reflect a major concern about the use of marijuana cigarettes for medical therapy as expressed by the Institute of Medicine. Although we did not measure other combustion products such as polycyclic aromatic hydrocarbons and oxidant gases, the observation of little or no CO exposure suggests little or no exposure to these other compounds. The vaporizer was well tolerated, with no reported adverse effects. Most subjects preferred the vaporizer compared to marijuana smoking, supporting its potential for medical therapy.
Finally, Mirken cites a 2007 study in the Harm Reduction Journal , showing
that respiratory symptoms like cough, phlegm, and tightness in the chest increase with cigarette use and cannabis use, but are less severe among users of a vaporizer. ... The odds ratio suggests that vaporizer users are only 40% as likely to report respiratory symptoms as users who do not vaporize, even when age, sex, cigarette use, and amount of cannabis consumed are controlled. The use of cigarettes in conjunction with cannabis exacerbated symptoms, as found in previous work.
So that's the case for vaporization. As to GW Pharmaceuticals' claim that its spray formulation helps patients "obtain symptom relief without experiencing a 'high,'" Mirken cites the spray's package insert, which says :
SATIVEX has two principal active components: THC and CBD. ...THC is a psychotropic agent which may produce physical and psychological dependence and has the potential to be abused. ... THC has complex effects on the central nervous system (CNS). These can result in changes of mood, decrease in cognitive performances and memory, decrease in ability to control drives and impulses, and alteration of the perception of reality, particularly altered time sense.
The company's argument is that Sativex
is composed primarily of a 1:1 ratio of two cannabinoids—CBD ... and THC. ... The CBD:THC formulation is believed to enhance the pain relief of THC while modulating the unwanted psychotropic and other THC-related side effects, such as tachycardia. The spray delivery system keeps THC from entering the blood too rapidly and also minimizes the development of unwanted psychotropic effects.
I don't see a claim here that the 1:1 ratio in Sativex has any direct effect on whether you get high. The effect seems to be through ad hoc dosage control by the patient, known as self-titration. And if that's the case, then preventing "THC from entering the blood too rapidly" is problematic, since, as we discussed above, it makes it more difficult to monitor and adjust your dosage.
I'll let science sort this one out. Thanks for the studies comparing marijuana vaporization to smoking. Vapor wins. Now let's see studies comparing vapor with spray.