The study was terminated because of difficulties recruiting subjects.

The primary hypothesis for this study is that, in nicotine-dependent tobacco smokers, baclofen will be superior to placebo for smoking abstinence measures.

The secondary hypothesis is that subjects assigned to the baclofen groups will exhibit higher rates of medication compliance (i.e. take the medication as directed for the trial period) than those in the placebo group.

The tertiary hypothesis is that baclofen will lead to significant reductions in tobacco withdrawal and craving ratings as compared to placebo.

This study will test a new medication strategy designed to help smokers quit. It will evaluate Baclofen, a drug currently approved and available in Canada as a myorelaxant. Forty five nicotine-dependent smokers will enroll in this study. Fifteen will receive placebo (inactive pill), fifteen will receive baclofen 30 mg/day, and fifteen will receive baclofen 60 mg/day. Once enrolled, subjects will visit CAMH on a weekly basis for assessment of smoking behaviour, a brief health check (vitals, BP and AE screening), delivery of brief individual smoking cessation counselling, and collection of breath, blood and urine samples (as scheduled) to a) measure levels of nicotine and its metabolites, b) conduct pregnancy and tox testing. The medication phase of this study lasts 12 weeks. Two follow-up visits will be scheduled at week 13 and at six months after trial completion.

Inclusion Criteria:

• Male or female adults (18 years or older).
• Meet DSM-IV criteria for nicotine dependence,
• Smoke ≥10 cigarettes/day,
• Baseline FTND score ≥4, CO level ≥10,
• have had at least one failed quit attempt in the past and are motivated to quit within 30 days of initial intake.
• No previous use of medication for smoking cessation in 1 month prior to randomization.
• BMI between 15 and 40 inclusive.

Exclusion Criteria:

• Meet DSM-IV criteria for a current diagnosis of major depressive disorder, panic disorder or post-traumatic stress disorder, or a current or past history of bipolar disorder or schizophrenia
• Have a past history of major depression, with historical evidence of suicidal or homicidal behaviour, or psychotic symptom,
• Have abused alcohol or other drugs of abuse (cocaine, opiates, benzodiazepines, etc) in 3 months prior to randomization
• Demonstrate serious medical conditions, unstable cardiovascular disease, significant blood abnormalities)
• Are pregnant, are trying to become pregnant or are currently breastfeeding
• Baclofen hypersensitivity .