Mason 2012.
| Methods | Randomised, double‐blind, placebo controlled trial | |
| Participants | Setting: outpatient with weekly clinic visits, California, USA. Scheduled duration 12 weeks Participants: 50 adults, seeking treatment, current cannabis dependence by DSM‐IV, smoked cannabis at least once in week prior to randomisation Group sizes: 25 in each group No significant group differences on demographic or clinical variables at baseline Mean age 33.9 years 88% male 62% employed full‐time; 40% married Mean 11.6 years of daily cannabis use, smoking a mean of 11.0 g/week Exclusion criteria: abuse or dependence on substances other than cannabis or nicotine, and significant psychiatric disorders |
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| Interventions | Group 1: oral gabapentin 300 mg/day, increasing to 1200 mg/day Group 2: placebo Abstinence‐oriented individual counselling weekly |
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| Outcomes | Change in amount of cannabis use, frequency of use and withdrawal symptoms, as graphs and results of statistical tests Number completing treatment Cannabis use by weekly urine toxicology and self‐report by TLFB interview Withdrawal symptoms by Marijuana Withdrawal Checklist Marijuana Problems Scale completed at baseline and end of treatment |
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| Notes | Funding: research grants (NIDA) 1 author declared past associations with pharmaceutical companies |
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| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | Quote: "subjects were randomly assigned … in a 1:1 ratio, on the basis of a computer‐generated randomization code." |
| Allocation concealment (selection bias) | Low risk | Quote: "The randomization code was kept by the study pharmacist, who provided subjects with a 1‐week supply of medication in a blister card package at each weekly study visit …" Comment: allocation by pharmacy would support adequate concealment of allocation. |
| Blinding of participants and personnel (performance bias) All outcomes | Low risk | Quote: "Subjects, care providers, and those assessing outcomes were blinded to the identity of drug assignment. Gabapentin was purchased and over‐encapsulated to match placebo capsules." |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | Quote: "Subjects, care providers, and those assessing outcomes were blinded to the identity of drug assignment. Gabapentin was purchased and over‐encapsulated to match placebo capsules." |
| Incomplete outcome data (attrition bias) All outcomes | Unclear risk | High rate of dropout. Extent of missing data, and adjustments for missing data unclear |
| Selective reporting (reporting bias) | Low risk | None apparent |
| Other bias | Low risk | None apparent |