Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Adverse effects
Systematic review	1814 women 23 RCTs in this analysis	All adverse effects with NSAIDs with placebo Absolute results not reported	OR 1.37 95% CI 1.12 to 1.66 P = 0.0018 The review reported that the most commonly reported adverse effects were mild neurological and gastrointestinal symptoms	Small effect size	placebo
Systematic review	702 women 13 RCTs in this analysis	Gastrointestinal adverse effects with NSAIDs with placebo Absolute results not reported	OR 1.47 95% CI 0.99 to 2.18 P = 0.059 Analysis included 2 RCTs of aspirin		Not significant
Systematic review	498 women 7 RCTs in this analysis	Neurological adverse effects with NSAIDs with placebo Absolute results not reported	OR 2.74 95% CI 1.66 to 4.53 P = 0.00008 Included events such as headache, drowsiness, dizziness, and dryness of mouth Analysis included 1 RCT of aspirin	Moderate effect size	placebo
RCT Crossover design 3-armed trial	149 women, aged 18–44 years, with primary dysmenorrhoea	Adverse effects 40/129 (31%) with celecoxib 46/126 (37%) with naproxen sodium 38/127 (30%) with placebo	The majority of adverse effects were related to primary dysmenorrhoea; the most common adverse effects included nausea, headaches, insomnia, dizziness, and constipation
RCT 3-armed trial	180 women with primary dysmenorrhoea	Adverse effects with mefenamic acid with placebo	The RCT reported nausea in 1 woman who received mefenamic acid but gave no further information