BACKGROUND AND AIMS: In some clinical studies men and women have been found to differ in their ability to quit smoking, perhaps as a result of progesterone. The primary aim of this study was to provide a preliminary test of whether progesterone (PRO), compared with placebo (PBO), was more effective for smoking cessation in men and women.
DESIGN: Pilot double-blind, placebo-controlled randomized clinical trial.
SETTING: Minneapolis/St Paul metro area, Minnesota, USA.
PARTICIPANTS: A total of 216 participants were randomized, including 113 men (18-60 years; PRO = 56, PBO = 57) and 103 women (18-50 years, pre-menopausal with self-reported regular menstrual cycles; PRO = 51, PBO = 52).
INTERVENTION: Participants were randomized (1 : 1 within sex group) to either PRO (200 mg twice daily) or PBO. Participants were assigned a quit date approximately 7 days after starting medication (luteal phase for women) and were followed for 12 weeks to assess relapse.
MEASUREMENTS: The primary outcome was self-reported 7-day point prevalence abstinence (PPA) at week 4. Secondary outcomes included 7-day PPA at weeks 8 and 12, prolonged abstinence, continuous abstinence, urine cotinine < 50 ng/ml, expired carbon monoxide <= 5 parts per million (p.p.m.) and days to relapse.
FINDINGS: There was a significant difference in 7-day PPA at week 4 among women [PRO: 18 (35.3%) versus PBO: 9 (17.3%), odds ratio (OR) = 2.61, 95% confidence interval (CI) = 1.04, 6.54, P = 0.041], but not among men [PRO: 13 (23.2%) versus PBO: 12 (21.1%), 1.13 (0.47, 2.76), P = 0.782]. There was some evidence that PRO delayed relapse in women (days to relapse; PRO: 20.5 ± 29.6 versus PBO: 14.3 ± 26.8, P = 0.03) but not in men (PRO: 13.4 ± 25.9 versus PBO: 13.3 ± 23.8, P = 0.69).
CONCLUSIONS: Oral micronized progesterone may aid smoking cessation in women.