Diamond 1968.

Study characteristics
Methods	Study design: randomised controlled trial. Trial duration: 12 weeks (11 April 1966 to 13 July 1966) Trial location: University of Minnesota Hospitals, Minneapolis, USA
Participants	Number of participants: 106 postpartum women aged 15 to 41 years Intervention group: 54 women (29 primiparous and 25 multiparous) Control group: 52 women (26 primiparous and 26 multiparous)
Interventions	Intervention: Bisoxatin acetate (3 tablets); 1 tablet was given orally 1st day postpartum and if no bowel action occur that 1st day, the dose was increased to 2 tablets on the 2nd day. If no bowel activity occur by the 3rd day, another form of laxative was used. Control: lactose placebo (3 tablets)
Outcomes	Primary outcomes 1. Number of participants having their first bowel movement by day 1, day 2, and day 3 2. Number of stools per day 3. Side effects: diarrhoea, loose or watery stool
Notes	Ethics approval: not stated Correspondence with authors: no email address available. We would have requested details regarding risk of bias, for instance whether random number tables or a computer were used in random sequence generation. Dates of study: study was conduct between 11 April 1966 and 13 July 1966 Funding sources: study was supported by the Wyeth Laboratories, Philadelphia, Pennsylvania, USA Declarations of interest: no comment provided
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote "Each patient was assigned a number according to a random code". It was unclear how the random sequence was generated.
Allocation concealment (selection bias)	Unclear risk	Quote "Identical envelopes and drugs were used". It was unclear whether adequate precautions were taken to conceal the assignment from the participants and investigators.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Quote "The patients and investigators were not aware of the content of the identical drugs and envelopes". Insufficient information on identical colour, shape, and size of drug to enable explicit judgement.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote "The knowledge of the random code number and type of drug was not revealed till the completion of the study".
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing outcome data. All women enrolled were included in the final analysis.
Selective reporting (reporting bias)	Low risk	No published protocol available, but all outcomes that were prespecified in the methods session were addressed.
Other bias	Unclear risk	The study was supported by Wyeth Laboratories, but the trial authors did not specify whether the drug company influenced the results.