This project will test whether gemfibrozil, a well-studied medication for high cholesterol, will help people stop smoking nicotine cigarette smoking. The study will also test whether gemfibrozil decrease cravings for cigarette and the desire to smoke.

This is a pilot clinical trial examining the feasibility and efficacy of gemfibrozil treatment for smoking cessation. Adults with a desire to quit nicotine cigarette smoking will be recruited. Eligible participants will be randomly divided into two groups: those who receive gemfibrozil and waitlist controls. Screening will be conducted with a brief phone screen followed by a longer screening visit for those who qualify. During the screening visit, all study participants will provide demographic information and will be interviewed regarding smoking history. Procedures performed during the screening visit include a blood draw, urine pregnancy test, physical exam, clinical psychiatric interview, and measurement of exhaled carbon monoxide (CO). At baseline, participants will complete the Heavy Smoking Index (HSI) and the Brief Questionnaire of Smoking Urges (QSU-Brief). Participants will also complete the Quick Inventory of Depressive Symptoms-Self Rated (QIDS-SR) to assess symptoms of depression and changes in mood associated with smoking cessation will be assessed with the Concise Associated Symptoms Tracking (CAST) scale . Participants will work with the research clinician to set a target quit date within one week of the baseline session, and all participants will be provided written materials with guidance for smoking cessation as part of a smoking cessation counseling session. All participants will attend visits at the research clinic at 3 days and 4 weeks from target quit date to assess safety, adherence, and smoking status; participants will also receive additional smoking cessation counseling. Smoking status will be determined with exhaled breath CO and a single item questionnaire regarding the number of cigarettes smoked since target quit date and symptoms of depression and mood changes will again be measured. Medication side effects will be quantified using the Frequency, Intensity, and Burden of Side Effects Rating (FIBSER) scale. The final study visit will occur at 8 weeks after target quit date for completion of the HSI, QIDS-SR, CAST, FIBSER, exhaled breath CO, QSU-Brief, and smoking self-report.

Inclusion Criteria:

• Age 18-64 years
• Meet DSM-5 criteria for tobacco use disorder based on cigarette use
• Desire to quit smoking
• Able to complete assessments and interview in English

Exclusion Criteria:

• Psychiatric co-morbidity posing safety risk, including current suicidality or psychosis as assessed on clinical interview
• Concurrent use of a statin medication (HMG-CoA reductase inhibitor),anticoagulant, or repaglinide
• Concurrent use of any FDA-approved medication for smoking cessation
• Use of any form of tobacco or nicotine (including vaporizer) other than cigarette smoking
• Any DSM-5 substance use disorder other than nicotine use disorder
• History of intolerance to any fibrate medication
• History of gallbladder disease and cholestectomy has not been performed
• Baseline liver function tests > twice the upper limit of normal
• Severe impairment of renal function (baseline serum creatinine ≥ 2 mg/dL)
• Currently pregnant or nursing