The difficulty some marijuana users have in reducing or stopping their use appears to be due to a dependence on marijuana; e.g, use of marijuana is to obtain the effects of the drug THC (tetrahydrocannabanol), there are cannabinoid receptors in everyone’s brains, and stopping marijuana can cause a withdrawal symptom. With other drug dependencies, supplying the active drug in a medication (e.g. using methadone in those with heroin dependence or nicotine replacement in tobacco smokers) has been successful; thus, providing THC via a medication might help marijuana users change. In fact, a cannabinoid medication (dronabinol or Marinol) has been used for many years to treat pain, nausea, and weight loss in cancer patients. Also, small studies have found dronabinol decreases marijuana withdrawal symptoms including craving. Historically, dronabinol has rarely been abused (probably because of its slow onset of action compared to smoked marijuana). Well, someone has finally tested whether dronabinol would help users quit (Levin et al. Drug and Alcohol Dependence 116:142, 2011). They found that the usual dose of dronabinol reduced withdrawal symptoms but did not increase quitting or reduction in use of marijuana. The study was well-done with almost all users taking the dronabinol faithfully and urine testing to prevent falsifications. I can think of only two possible explanations of these negative results: the dose was not high enough and/or they did not study marijuana users who really wanted to change. Certainly the former explanation, not using a high enough dose, reflects the problem we observed when first testing these types of medications for heroin and nicotine dependence. Of note, the few other medications for marijuana cessation or reduction that have been tested have not looked highly promising.
–Dr. John R. Hughes