Misra 2013.

Methods	Study design: randomized controlled trial (2 arms) Study duration: not reported Study setting: hospital, single centre, India
Participants	Adults undergoing elective craniotomy for tumour resection who were receiving preoperative intravenous (IV) dexamethasone for at least 48 hours (n = 79) Inclusion criteria Adults undergoing above surgery Exclusion criteria Pregnancy Breast feeding Patients on preoperative anti‐emetic, gabapentin or pregabalin Patients with an allergy to any study drug Renal dysfunction Significant nausea or vomiting preoperatively Emergency craniotomy Mean age, range (years) 39 (18 to 60) Numbers allocated to each arm Group intervention (n = 39) Group control (n = 40) Male gender Group intervention: 20/36 (participants analysed) Group control: 20/37 (participants analysed)
Interventions	Technique and timing Gabapentin 600 mg orally, given 2 hours before surgery versus vitamin B placebo given at the same time point Dosage 600 mg
Outcomes	Primary Incidence of nausea and vomiting in the first 24 hours after surgery Secondary Postoperative pain scores as measured on a scale of 0 to 3 Incidence of moderate/severe pain Intraopertive anaesthetic requirement Postoperative narcotic consumption Postoperative nausea and vomiting
Notes	Funding None
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: ''randomisation was done by means of a computer‐generated random number scheme.'' Patients were allocated to receive either placebo (vitamin B‐complex capsule) (group D) or 600 mg of gabapentin (group GD), administered orally, 2 hours before the induction of anaesthesia by means of a sealed envelope.
Allocation concealment (selection bias)	Low risk	Quote: ''patients were allocated to receive either placebo (vitamin B‐complex capsule) (group D) or 600 mg of gabapentin (group GD), administered orally, 2 hours before the induction of anaesthesia by means of a sealed envelope''.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Placebo tablets were used to blind participants.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	6 participants were lost to follow‐up: 3 in each group due to delayed extubation. An intention‐to‐treat analysis was not used.
Selective reporting (reporting bias)	Low risk	Outcomes reported as specified
Other bias	High risk	Small study and no sample size calculation provided