Karabayirli 2012.

Methods	Location: probably Turkey (location of investigators) Recruitment time: not reported Sample size calculation and outcome of focus: Based on initial pilot measurements, assuming SD within each group approximately 1.8, maximum difference of mean pain score (10‐point VAS) was 1.5, sample size of 29 in each group was calculated with power 80% and alpha .05
Participants	General with N: 103 women Source: not reported; possibly university clinic Inclusion criteria: healthy (physical status ASA I) multiparous women of childbearing age (18 to 49 years), scheduled for IUD insertion Exclusion criteria: known allergy or hypersensitivity to NSAIDs or tramadol hydrochloride; current use of narcotic or NSAID; history of epilepsy, peptic ulcer disease, bleeding disorder, asthma, or hepatic or renal failure; nulliparity; delivery within 12 months, and breastfeeding at time of insertion
Interventions	1) Naproxen sodium 550 mg (Apranax Fort tablets) 2) Tramadol HCl 50 mg (Contramal capsules) 3) Placebo (empty capsules) Timing: 1 h before insertion of IUD
Outcomes	Primary: pain score immediately after IUD insertion (10‐point VAS, with 10 meaning 'worst imaginable pain') Secondary: side effects, satisfaction and preference
Notes	IUC used: Multiload Cu 375 Standard
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated table of random numbers
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Participants and involved physicians of obstetrics and gynecology were blinded to the study.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Loss to follow‐up: none