Omar 2011.

Methods	Blinded, randomized, controlled, parallel‐group, multidose trial. Intervention start at the ‘end of surgery’.
Participants	Type of surgery: elective cesarean section Paracetamol group Entered/completing: 40/40 Age (mean, SD): 30.80 ± 4.79 Sex (male, %): 0 Normal saline group Entered/completing: 40/40 Age (mean, SD): 29.60 ± 5.20 Sex (male, %):0
Interventions	Paracetamol: 1 g IV in 100 cc start at end of surgery, then every 6 h x 24 h Control: 100 cc NS start at end of surgery, then every 6 h x 24 h All: every participant received 0.2 mg intrathecal morphine at the time of spinal placement. Clinically this intervention has an expected duration of action of up to 18 h. Pethidine for rescue analgesia
Outcomes	Primary: number of participants requiring rescue analgesic drug use x 24 h Secondary: visual analog scale (VAS) was used to evaluate pain level (0 = no pain to 10 = worst pain) at 6, 12 and 24 h postoperatively by a resident and nurse who did not know about the treatment protocols. Satisfaction was evaluated at 12 and 24 h postoperatively (1 = very unsatisfied to 5 = very satisfied).
Source of funding	None mentioned
Were treatment groups comparable at baseline?	Yes, but no data on surgical duration or whether or not a participant had a repeat cesarean section
Details of preoperative pain	Participants with history of chronic abdominal pain or treated with analgesics were excluded from the study
Notes	No enrolment flow chart. When a spinal failed, a participant was dropped, likewise for participants with intraoperative complications for example, but unclear when participants were enrolled or randomized.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Table of randomization
Allocation concealment (selection bias)	Low risk	Sealed envelope
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Participant blinding not addressed. Personnel blinding per statement except that the chief resident was not blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported. Appears that all participants completed the study.
Selective reporting (reporting bias)	High risk	Very limited outcomes (rescue analgesia, pain, and satisfaction scores). No side effects addressed at all.
Size	High risk	Fewer than 50 participants per arm of the study (40 paracetamol, 40 placebo)