Akiyama 1999.

Methods	Randomised single‐centre cross‐over trial Duration of study: 8 months
Participants	Country: Japan Population: infertile men, N = 10 Mean age: 36 years (treatment group age range 24 to 49 years, control age range 30 to 37 years) Inclusion criteria: male infertility (ROS > 5 x 10,000 counts/10,000,000 viable spermatozoa) Exclusion criteria: azoospermia, pyospermia
Interventions	Ethylcysteine 600 mg (n = 5) versus Vitamin E 600 mg (n = 5) Duration of treatment: 3 months, with a one month wash out, then cross‐over for another 3 months. Only data from the first phase were used in data analysis
Outcomes	Sperm parameters, blood serum and seminal plasma levels of ethylcysteine and vitamin E
Notes	In Japanese. Data extraction translated by Ichiro, a colleague of Samantha Roberts, 29.01.2009 Author contacted 'no further information is available'
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Patients were divided randomly"
Allocation concealment (selection bias)	Unclear risk	Not mentioned
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not mentioned
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not mentioned
Incomplete outcome data (attrition bias) All outcomes	Low risk	No incomplete outcome data
Selective reporting (reporting bias)	Unclear risk	Sperm parameters reported. No protocol available.