Methods	Randomised, double-blind, placebo-controlled 4-period cross-over, no enrichment. No imputation method mentioned (but if half of scores missing, outcome considered missing) Titration to target doses or limit of tolerability over 3 weeks, then stable dose for 1 week, and tapered dose for 1 week (5 weeks in total); 3-day washout and cross-over to next treatment
Participants	PDN and PHN. N = 57, median age 62 years, 44% women. Pain ≥ moderate for 3 months, initial mean pain score 5.8/10
Interventions	Gabapentin 3200 mg daily (max) Morphine 120 mg daily (max) Gabapentin plus morphine 2400 mg/60 mg daily (max) Placebo (lorazepam) 1.6 mg Mean maximum tolerated doses: gabapentin alone 2207 ± 89 mg, morphine alone 45. 3 ± 3.9 mg, gabapentin + morphine 1705 ± 83 + 34.4 ± 2.6 mg
Outcomes	Pain relief for those completing a given treatment (5-point scale) Withdrawals
Notes	Oxford Quality Score: R = 2, DB = 2, W = 1, Total = 5
Risk of bias
Item	Authors’ judgement	Description
Allocation concealment?	Yes	“concealed allocation schedule” prepared remotely
Blinding? All outcomes	Yes	“identical appearing blue and grey capsules …. in accord with a double-dummy design”
Incomplete outcome data addressed? Efficacy	Unclear	Imputation not mentioned
Size Efficacy	No	Although 57 randomised, data available 40-44 completing a given treatment
Study duration Efficacy	Unclear	5 weeks each period
Outcomes reported	Unclear	At least moderate pain relief