The effect of dydrogesterone on premenstrual symptoms. A double-blind, randomized, placebo-controlled study in general practice.

The effect of dydrogesterone on premenstrual symptoms was investigated in a double-blind, randomized, placebo-controlled study comprising 161 patients from unselected practice material. Dydrogesterone 10 mg twice daily from the 12th day until onset of the following menstrual period was compared with placebo throughout 3 cycles. No clinically relevant effect of dydrogesterone was found. There was an overall therapeutic effect in 52% of the patients on dydrogesterone, and in 44% of the placebo-treated patients. Therapeutic gain ranged between -7 and +23% (95% confidence limits). Type II error risk of failure to detect a therapeutic gain of 20% was 6%. A significant effect of dydrogesterone was found on decreased libido, and statistical significance was nearly achieved for the symptoms irritability and headache. The significant effect on libido can be attributed to mass significance.