Kantor 1984a.

Study characteristics
Methods	Randomised controlled trial Sample size calculation not stated
Participants	Setting: single‐centre study, Bellevue Hospital, New York. Time not given Inclusion criteria: postpartum women who complained of moderate or severe uterine cramp pain (review authors have assumed vaginal birth) Exclusion criteria: women breastfeeding; previous severe adverse reactions to narcotics; treated with other analgesia or sedative‐tranquillisers; severe renal, hepatic, cardiac or neurological deficits; history of drug abuse
Interventions	Women were randomly allocated to 1 of 3 treatment groups and given 1 dose of study medication followed by observations at 30 minutes and hourly for 6 hours Single dose of oral nalbuphine 15 mg (N) (N = 35) Codeine 60 mg (C) (N = 37) Placebo (P) (N = 36)
Outcomes	Need for additional analgesia: number of women who dropped out or required additional analgesia were recorded
Notes	The formulation of codeine (phosphate or sulfate) is not stated 121 women randomised (N = 39, C = 42, P = 40), 3 post‐randomisation exclusions (1 from each group). Women with episiotomy pain were included and most of the analyses included all women. There were 3 episiotomy women in N, 4 in C and 3 in P Dates of study: not stated Funding sources: none stated Declarations of interest: none stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information to make a judgement. Study described as "randomized"
Allocation concealment (selection bias)	Unclear risk	Insufficient information to make a judgement
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Insufficient information to make a judgement
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Insufficient information to make a judgement
Incomplete outcome data (attrition bias) All outcomes	Low risk	3 of the women randomised were excluded from analyses because of "administrative deviations from protocol". There were 35 women allocated to the nalbuphine group, 37 women to the codeine group and 36 women to the placebo group. Quote: "Subjects were excluded if they had previous severe narcotic adverse events, or had severe renal, hepatic, cardiac, of neurologic deficits. Patients with a history of drug abuse and nursing mothers were excluded." The study does not report which treatment group the excluded women had been allocated to. There was 2% attrition of randomised participants. 27 women required additional analgesia toward the end of the 6‐hour post‐treatment observation, did not complete the 6‐hour period of observation, but all after the 2nd hour and were therefore included in outcome reporting. (14 women in the placebo group, 8 women in the nalbuphine group and 5 women in the codeine group).
Selective reporting (reporting bias)	Unclear risk	No published protocol or trial registration available
Other bias	Unclear risk	Unclear if randomisation was stratified by source of pain; uterine cramp or episiotomy, only 1 outcome reported separately