Summary of findings 1. Norethisterone compared to placebo for seizures in catamenial epilepsy.

Norethisterone compared to placebo for seizures in catamenial epilepsy
Patient or population: women with seizures due to catamenial epilepsy Settings: outpatients Intervention: norethisterone Comparison: placebo
Outcomes	Illustrative comparative risks* (95% CI)		Relative effect (95% CI)	No. of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Placebo	Norethisterone
Seizure freedom Follow‐up: NA	Outcome not reported.				NA
Responder rate Follow‐up: NA	Outcome not reported.				NA
Change in seizure frequency Follow‐up: up to 14 months	Neither of the studies showed any significant differences between treatments in terms of seizure frequency.		NA	24 (2 cross‐over studies)	⊕⊝⊝⊝ very low1	1 of the studies also considered tonic‐clonic and complex‐partial catamenial seizures separately. No significant differences were found between treatments by seizure type.
Number of withdrawals from the study Follow‐up: up to 14 months	Neither of the studies reported any treatment withdrawals.		NA	24 (2 cross‐over studies)	⊕⊝⊝⊝ very low1
Adverse events Follow‐up: up to 14 months	4 "mild" types of adverse event considered to be related to the trial medication were reported: irregularities in menstrual cycle (5 women), facial rash (1 woman), headaches (2 women), mild swelling of hands and feet (1 woman), and bloated feeling (1 woman).		NA	15 (1 cross‐over study)	⊕⊝⊝⊝ very low1	It is assumed that these events occurred whilst women were taking norethisterone (and no events were reported in the placebo group), but this is not explicitly stated.
Quality of life Follow‐up: NA	Outcome not reported.				NA
*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; NA: not applicable
GRADE Working Group grades of evidence   High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect.

¹Downgraded three times due to serious imprecision and risk of bias: the two included studies used a cross‐over design, had a very small sample size, and reported limited information regarding study design and numerical results.