Effect of progesterone and its 5 alpha and 5 beta metabolites on symptoms of premenstrual syndrome according to route of administration. Investigation of the efficacy of progesterone pessaries in the relief of symptoms of premenstrual syndrome. progesterone Study Group.
Orally administered progesterone may have advantages over other routes of administration in the treatment of premenstrual syndrome (PMS) because of substantially higher levels of the anxiolytic metabolites 5 alpha and 5 beta pregnanolone. The only previous placebo-controlled trial which used oral progesterone reported beneficial effects in the treatment of PMS. The present study, a double-blind crossover trial, compared the administration of 300 mg daily oral progesterone with 200 mg daily vaginal progesterone and matched placebos for 10 days premenstrually. Although there was a significant treatment effect on symptoms, no difference between active treatments and placebo was found. The trial was terminated with 25 women completing treatment as it was evident that no clinically significant effect of either form of progesterone was likely to be detected even with twice the sample size. Serum levels of progesterone and metabolites showed that oral administration resulted in supraphysiological levels of 5 alpha and 5 beta metabolites and there was a negative correlation between 5 alpha pregnanolone levels and anxiety. However, this did not translate to overall reduction in premenstrual distress or anxiety beyond that achieved by placebo, as measured by validated questionnaires. A variety of definitions have been applied to premenstrual syndrome. The severity of the syndrome is also variable.
                A study was undertaken to compare progesterone pessaries with placebo in the relief of symptoms of premenstrual syndrome. In this study the condition was characterized by a wide range of symptoms recurring in the late luteal phase but absent in the follicular phase (that is, the specific definition published by Dalton in 1953).
                A multicentre, prospective, double-blind, randomized, parallel group study was undertaken by 45 general practitioners. Patients were deemed eligible after two prospective menstrual cycles of observation (selection phase) in which a precise definition of symptoms was applied. Patients were randomized to use either progesterone pessaries (400 mg twice a day) or matching placebo, by vaginal or rectal administration, from 14 days before the expected onset of menstruation until the onset of vaginal bleeding, for four consecutive cycles. Baseline data for the outcome variables were determined in the selection phase. The main outcome variables were changes in the severity (categorized as none, mild, moderate or severe) of each patient's most severe symptom, and in the average score of all the patient's symptoms characteristic of premenstrual syndrome. Spontaneous reports of adverse events were recorded.
                A total of 281 patients were screened for premenstrual syndrome; of these, 141 patients were randomized to treatment or placebo groups. Efficacy was evaluated in 93 patients. Reductions in the scores of the highest scoring, most severe, symptoms and in the average symptom score, were consistently observed in patients receiving progesterone pessaries and in those receiving placebo. The response to progesterone was greater than to placebo during each cycle; the differences were clinically and statistically significant. Adverse events were reported by 51% of patients in the progesterone treatment group and by 43% in the placebo group. Irregularity of menstruation, vaginal pruritus and headache were reported more frequently by patients taking active therapy.
                In this study, progesterone, given as pessaries by vaginal or rectal administration, was more effective than placebo in the relief of symptoms of premenstrual syndrome in a population of patients selected by strict entry criteria.
The trials did not show that progesterone is an effective treatment for PMS nor that it is not. Neither trial distinguished a subgroup of women who benefited, nor examined claimed success with high doses.