Kava: a natural aid to kick the smoking habit?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * adults aged 21 years or above (legal age for smoking in the U.S.) up to 75 years old; * self-reported smoking at least 5 cigarettes/day for the past year with INTENTION to quit at time of screening visit; * expired carbon monoxide level of more than 8 ppm at recruitment; * willingness to participate in the proposed study, as indicated by signed informed consent; * access to a functional telephone; * expected presence in the study's geographical area for the next 4 months; * not currently enrolled in any smoking cessation programs per self report; and * female subjects of childbearing potential will be required to practice acceptable methods of birth control (the acceptable methods of birth control include birth control pills, Birth Control Shot, Birth Control Implant, IUD, Diaphragm, and cervical cap). * if a participant takes kava dietary supplement, a 2-week washout period is needed for the participant to initiate this study or if a participant participated in a kava trial before, such as the kava JEK trial, the participant could be enrolled if the inclusion criteria above are met, including the 2-week washout period. Exclusion Criteria: * history of active cancer (other than non-melanoma skin cancer) within the past 2 years; * diagnosed with liver dysfunction or with previous liver diseases; * levels of alanine transaminase, aspartate transaminase, alkaline phosphatase or total bilirubin over limit of normal (ULN) range at prescreen; * inability to refrain from acetaminophen, alcohol (no more than one drink daily via self-report), or other potentially hepatotoxic substances; * are pregnant or nursing (lactating) or of childbearing age planning to become pregnant or unwilling to use adequate contraception during the study; * participant answered "Yes" to any of the Modified Ask Suicide Screening Questions questions 1 through 3, or refuses to answer all of the questions. If subject answers 'Yes' to question 4 but the most recent suicide attempt took place \>12 months from screening visit then subject is still eligible.