A placebo-controlled study of effects of oral progesterone on performance and mood.

1. Oral micronized progesterone (P) is proposed for the treatment of certain endocrine gynaecological disorders. To examine the effects of P on performance and mood, a randomized, placebo-controlled study of 24 healthy females ages 18-24 years on low-dose oral contraceptives was conducted. 2. Subjects were admitted to the Clinical Research Center on four occasions and received single doses of oral P (300, 600, 1200 mg) or placebo. Blood sampling, psychometric tests and mood scales were administered at baseline and at hourly intervals for 6 h. 3. P doses produced significant dose-related but highly variable increases in plasma P concentrations. Fatigue increased with P doses, although few subjects were objectively drowsy. Very high peak plasma P concentrations, achieved by some subjects at the 1200 mg dose, were associated with decreased information processing and verbal memory function as well as fatigue. 4. We conclude that oral P can safely be prescribed at higher than previously-reported doses, based on evidence of transient behavioural effects only at the highest doses in some subjects who achieved high plasma P concentrations.