A Phase II study of St. John's Wort for smoking cessation.

Objectives: To examine the feasibility and efficacy of St. John's Wort (SJW) for smoking cessation.

Design: This one-arm Phase II study utilized an exact two-stage group sequential design with a 1-week run-in period between the start of SJW treatment and the designated quit date. A total of 37 smokers (ages 18-65 years, smoking > or = 10 cigarettes/day) were started on SJW. Thirteen failed to make a verified quit attempt on the predesignated date and were taken off study resulting in 24 evaluable subjects.

Setting: Smokers completed clinic visits at a cancer center with interval telephone calls and mailings.

Intervention: Standardized SJW, 450 mg capsules taken orally twice daily along with cessation counseling messages.

Main Outcome Measures: Subjects completed validated surveys and a focused physical examination at baseline. Evaluable subjects were defined as those subjects who made a confirmed quit attempt on their "quit date" 1 week following initiation of SJW. Smoking status was determined through self-report and bioverification using carbon monoxide (CO) testing.

Results: Among evaluable subjects, the 12-week quit rate was 37.5% (9/24). Quitters had no significant change in weight from baseline to 12-weeks cessation. Use of SJW was generally well tolerated.

Conclusions: Based upon these results (which suggest that SJW may be effective in maintaining smoking cessation) and the high compliance and few AEs, we conclude that SJW demonstrates feasibility for use in smoking cessation. If SJW proves to be effective in larger controlled studies, it could represent a less expensive, more readily accessible and well-tolerated agent to promote tobacco cessation.