Richmond 1993.

Methods	Study design: parallel‐group randomized controlled trial Sample size: 76 Country: UK Setting: secondary care hospital Dates conducted: not reported Postoperative opioid used and delivery: PCA morphine Pain score collection: not reported Concurrent postoperative analgesics: none reported
Participants	Inclusion criteria ASA 1 and 2 Undergoing elective total abdominal hysterectomy Exclusion criteria Chronic pain Regular intake of analgesics Psychiatric illness
Interventions	Group IV Pre (23 participants): intravenous morphine 10 mg administered at induction Group IV Post (21 participants): intravenous morphine 10 mg administered at peritoneal closure Also reports that saline placebo was used
Outcomes	Morphine consumption (mg at 24 hours) Pain sensitivity and postoperative pain (rest and movement on 0‐to‐100‐millimetre VAS at 4, 24, and 48 hours)
Notes	Funding: author recipient of Bristol‐Myers Squibb research grant. Role in published study unclear Declarations of interest: as above Authors contacted: no Other: pain score data extracted from graph and standard deviations estimated. Study also included a further group who were administered intramuscular morphine but we did not include this group in review as different route of administration.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No mention. Quote: "patients were randomly allocated"
Allocation concealment (selection bias)	Low risk	Performed by pharmacist. Quote: "were randomly allocated by a pharmacist"
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Saline used as placebo. Pharmacy made up study medications blind. Quote: "the study was double blind"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Reported as blinded. Quote: "the study was double blind"
Incomplete outcome data (attrition bias) All outcomes	High risk	Number of participants who dropped out for the reasons listed and to which groups they belonged is unclear from text. 1 reason for dropout was severe nausea, which could bias outcome of morphine consumption. Quote: "16 were excluded ... or severe nausea"
Selective reporting (reporting bias)	Unclear risk	No protocol or trial registration
Other bias	Low risk	Similar baseline characteristics. 1 of the investigators received industry funding, but it was unclear if the funding was specific to this study. Quote: "the groups were not statistically different"