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Vitamin B-6 for premenstrual syndrome

Clinical bottom line: Based on limited information from poor quality trials, vitamin B-6 may be of benefit in reducing the symptoms of premenstrual syndrome, including depressive symptoms. Further trials are required to confirm this finding and to assess appropriate doses and risk of harm, including toxicity.


Premenstrual syndrome (PMS) can be described as regularly recurring psychological and/or somatic symptoms during the luteal phase of the menstrual cycle and which are relieved by onset of menstruation. Vitamin B-6 deficiency is rare, with recommended daily allowance set at around 2 mg/day. Excessive ingestion (2000-6000 mg) causes peripheral neuropathy.

Systematic review

Wyatt KM, Dimmock PW, Jones PW, O'Brien PMS. Efficacy of vitamin B-6 in the treatment of premenstrual syndrome: systematic review. BMJ 1999; 318, 1375-1381.

Date review completed: 1998

Number of trials included: 10 (9 included in the meta-analysis)

Number of patients: 940

Control group: placebo

Main outcomes: improvement in overall PMS symptoms

Inclusion criteria were randomised placebo controlled double-blind trials of vitamin B-6 for premenstrual syndrome; parallel group design (or equivalent data extractable); vitamin B-6 preparations or multivitamin preparations with at least 50 mg of vitamin B-6; any language.

Odds ratios with 95% confidence intervals were calculated from dichotomous data reported in the trials (random effects model). Where this was not available, reviewers either generated dichotomous data by categorising patients as better (a subjective improvement reported) or not better (no change or worsening of symptoms), or used standardised mean differences to generate an odds ratio.

Findings

Ten trials met inclusion criteria. One was excluded from the analysis because of heterogeneity. Trials were generally poor of quality, with possible contamination from oral contraceptive use. Included patients ranged from self-diagnosed to hospital populations. Outcome measures included changes in mastalgia, depression and associated symptoms, swollen breasts, pain. Doses of vitamin B-6 ranged from 50 to 600 mg/day.

Combined odds ratio of the nine trials was 2.32 (1.95 to 2.54) indicating significant benefit of vitamin B-6 over placebo. Based on the odds ratios of each trial, six of the nine trials suggested significant benefit (lower confidence interval did not cross 1). There was no dose response.

Five trials reported on vitamin B-6 for depressive symptoms. The combined odds ratio was 2.12 (1.80 to 2.48) suggesting benefit with vitamin B-6.

Adverse effects

Reporting was not consistent, making assessment of adverse effects difficult. Minor adverse effects and study withdrawals were experienced in active and placebo groups. Vitamin B-6 toxicity: only one patient reported adverse effects that could be attributed to neuropathy associated with pyridoxine toxicity. However, trials were of relatively short duration, data collection was poor, and these symptoms may have been missed.

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