Cannabis use disorders are a significant public health concern and the absence of effective medications is a critical barrier to overcome. This application is founded on promising results from our laboratory suggesting that drugs that act at a2d-1 subunit containing voltage-dependent calcium channels (VDCCs) and/or elevate g- aminobutyric acid (i.e., GABA) will be effective medications for cannabis-use disorders. Our laboratory results are supported by a recent pilot clinical trial showing that gabapentin, which is a VDCC ligand and elevates GABA, reduced cannabis use in dependent, treatment-seeking adults. The goal of the present proposal is to build upon these promising laboratory and clinical findings by determining the ability of outpatient maintenance on pregabalin, a "next generation" VDCC ligand, and tiagabine, a GABA reuptake inhibitor, to attenuate the reinforcing effects of cannabis. Pregabalin will be tested because, although their mechanism of action is the same, the pharmacokinetic profile of pregabalin is improved compared to gabapentin, and clinical results suggest that this translates into greater pharmacotherapeutic effectiveness. Tiagabine will be tested because its effects overlap with gabapentin and pregabalin, GABA elevation is a possible mechanism for gabapentin's effects on cannabis use, and our recent data demonstrated that tiagabine produced a profile of effects that was comparable to gabapentin when tested in combination with D9-THC. Outpatient maintenance dosing will be tested because it more closely resembles the clinical treatment situation. Cannabis self-administration using a concurrent progressive-ratio drug-money choice procedure will be the primary outcome because drug seeking and drug taking behaviors, and the choice to use drugs to the exclusion of other behaviors, are defining characteristics of drug dependence, and drug self-administration procedures are predictive of therapeutic efficacy. Cannabis use in the natural environment will also be monitored during drug maintenance as a secondary outcome to optimize resource management and quicken the pace of intervention development. Our preliminary data with the proposed procedures support the feasibility of the project, the assembled research team is highly qualified and the environment will significantly contribute to the success of the research. The proposed project is innovative because it employs a novel hybrid procedure to study the impact of medication maintenance on direct cannabis effects in the laboratory as well as cannabis use in the natural environment, the effects of pregabalin and tiagabine on cannabis self-administration have not been tested previously, and a novel, real-time medication maintenance compliance technology will be implemented. Positive findings will exert an immediate and sustained impact by rapidly advancing currently available medications for the treatment of cannabis-use disorders, promoting novel pharmacological targets for further medications development and providing valuable basic science information about the mechanisms underlying cannabis reinforcement.
Cannabis is the most commonly used illicit drug in the United States, and its use is associated with rates of development of abuse and dependence, treatment admission and relapse that are comparable to other illicit drugs that are often perceived as more harmful. Currently there are no effective pharmacological treatments for cannabis-use disorders. This project will evaluate pregabalin and tiagabine for cannabis-use disorders using state-of-the-art human laboratory methods.