Methods	Randomised, double-blind, placebo-controlled 3-period cross-over, no enrichment. No imputation method mentioned Titration to target doses or limit of tolerability over 24 days, then stable dose for 1 week, and tapered dose for 1 week (6 weeks in total); 6-day washout and cross-over to next treatment
Participants	PDN and PHN. N = 56, median age 64 years, 40% women. Pain ≥ moderate for 6 months, initial mean pain score 5.4/10
Interventions	Gabapentin 3600 mg daily (max) Nortriptyline 100 mg daily (max) Gabapentin plus nortriptyline 3600 mg/100 mg daily (max) Mean (SE) maximum tolerated doses: gabapentin alone 2433 ± 106 mg, nortriptyline alone 62 ± 3.6 mg, gabapentin + nortriptyline 2180 ± 108 + 50 ± 3.5 mg
Outcomes	Pain relief (average) Withdrawals Adverse events
Notes	Oxford Quality Score: R = 2, DB = 2, W = 1, Total = 5
Risk of bias
Item	Authors’ judgement	Description
Allocation concealment?	Yes	“concealed allocation”
Blinding? All outcomes	Yes	“double dummy”
Incomplete outcome data addressed? Efficacy	Unclear	Imputation not mentioned
Size Efficacy	No	Reporting on < 50 completing 2 periods
Study duration Efficacy	Unclear	5-week period on treatment
Outcomes reported	No	No dichotomous data