Methods	RCT 2-arm parallel group design.
Participants	Brazil: hospital. 56 women. No information in abstract about participant inclusion criteria or characteristics
Interventions	Experimental: IM nalbuphine 10 mg. Control: IM pethidine 100 mg.
Outcomes	Analgesia and side effects. Neonatal: Apgar score.
Notes	Abstract only: insufficient information about participants. Not reported if > 1 dose given or anti-emetic.
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Described as “randomly selected” but not explained how.
Allocation concealment (selection bias)	Unclear risk	Not mentioned.
Blinding (performance bias and detection bias) Women	Unclear risk	Not mentioned.
Blinding (performance bias and detection bias) Clinical staff	Unclear risk	Not mentioned.
Blinding (performance bias and detection bias) Outcome assessor	Unclear risk	Not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Not mentioned.
Selective reporting (reporting bias)	Unclear risk	Impossible to decipher.
Other bias	Unclear risk	Impossible to decipher.