Effect of exogenous progesterone administration on smoking topography.

INTRODUCTION: Progesterone has been implicated as protective against drug taking behaviors, including combustible cigarettes. While prior research indicates higher endogenous progesterone levels are associated with a reduction in smoking intensity (as measured by smoking topography), it is unknown if exogenous delivery of progesterone may have the same effect. METHODS: This double-blind, counterbalanced, cross-over randomized trial enrolled women between the ages of 18 and 40 who smoked at least five cigarettes per day and were currently using oral contraceptives. After overnight abstinence participants attended two topography lab sessions. One lab session was conducted during progesterone (200 mg twice per day) treatment and the other was during placebo treatment. Analyses included linear mixed effect models to examine the effect of exogenous progesterone administration and endogenous progesterone values on topography outcomes. RESULTS: Participants (n = 43) were 23.8 (standard deviation [SD] ± 4.5) years old, smoked 10.5 (SD ± 3.7) cigarettes per day. Compared to placebo administration, progesterone administration reduced cumulative puff volume by 300 mL (95% confidence interval [CI]: -536, -65; p-value = 0.01) with additional trends indicating possible reductions in the number of puffs, average puff volume, and average flow. There were no significant effects of endogenous progesterone on smoking topography outcomes. CONCLUSIONS: Progesterone administration has the potential to reduce smoking intensity after overnight abstinence in women of reproductive age. Additional research is needed to explore how this may relate to smoking cessation outcomes in women of reproductive age.