A Cochrane review included 41 studies with a total of 4935 subjects. Gonadotrophin-releasing hormone analogues (GnRHas) were more effective at symptom relief than no treatment/placebo in one trial (RR 3.93, 95% CI 1.37 to 11.28; n=35). There was no statistically significant difference between GnRHas and danazol in 7 trials for dysmenorrhoea (RR 0.98, 95% CI 0.92 to 1.04; n=666) or pelvic pain (RR 0.96, 95% CI 0.86 to 1.07; n=647). More adverse events were reported in the GnRHa group. There was a benefit in overall resolution for GnRHas (RR1.10, 95% CI 1.01 to 1.21) compared with danazol. There was no statistically significant difference in overall pain between GnRHas and levonorgestrel-releasing intrauterine device (SMD -0.25, 95% CI -0.60 to 0.10; 3 trials, n=129). Evidence was limited on optimal dosage or duration of treatment for GnRHas. No route of administration appeared superior to another.
Comment: The quality of evidence is downgraded by risk of bias (unclear allocation concealment or blinding in half of the studies).