Table 3.

Summary of outcomes and key findings.

Studies	Summary of primary and secondary outcomes at the end of studies	Key findings
Backonja et al., 2008	NPRS: Mean reduction of score is higher in treatment group (29.9%) than control group (20.4%).	Capsaicin (NGX-4010) is safe and efficacious in reducing pain in postherpetic neuralgia patients.
	PGIC: Slightly improved, much improved and very much improved higher in treatment group (55%) compared to control (43%).
	Adverse reaction: Short lasting pain and erythema is generally mild and moderate in treatment group.
Webster et al., 2010a	NPRS: Mean reduction of score is significantly higher in treatment group (25.0%) than control group (14.7%) PGIC: Total improved (slightly, much and very much improved) higher in treatment group (55%) than control group (41%). CGIC: Total improved (slightly, much and very much improved) higher in treatment group (52%) than control group (42%). Adverse reaction: Mild to moderate, transient side effects are observed. Generally well-tolerated. 1% of participants withdrawn due to side effects. 59% of treatment group patient reported adverse events. No serious adverse events are related to treatment.	Capsaicin (NGX-4010) is efficacious in pain reduction in postherpetic neuralgia. Lowest effective dose is required in 60-min treatment.
Webster et al., 2010b	NPRS: Mean reduction of score is higher in treatment group (36.6%) than control group (32.3%) (but no statistical significance). PGIC: Much improved and very much improved in treatment group (43%) is higher than control group (30%) (but no statistical significance). CGIC: Total improved (slightly, much and very much improved) higher in treatment group (43%) than control group (24%). Adverse reaction: Generally well-tolerated in most participants and side effects are manageable in most cases. 4% of participants withdrawn due to burning and pain at application site. 75% of treatment group patient reported adverse events. No serious adverse events related to treatment.	Although, capsaicin (NGX-4010) appeared to be safe and well-tolerated, it failed to show significant efficacy in participants with postherpetic neuralgia for less than 6 months.
Irving et al., 2011	NPRS: Mean reduction of score is higher in treatment group (32.3%) than control group (25%). PGIC: Total improved (slightly, much improved and very much improved) higher in treatment group (61%) than control group (47%). CGIC: Total improved (slightly, much improved and very much improved) higher in treatment group (63%) than control group (48%). Adverse reaction: Higher occurrence in treatment group. Generally well-tolerated. 2% of participants withdrawn due to side effects. There is mild to moderate skin reactions at application site. No serious adverse events are caused by intervention.	Capsaicin (NGX-4010) is efficacious in pain reduction for postherpetic neuralgia.
Watson et al., 1993	Patients with PHN for more than 6 months Visual analog pain scale: Mean reduction is slightly higher in treatment group (20.9%) than control group (5.8%). PGIC: Total improved higher in treatment group than control group. 65% of treatment group versus 34% of the patients experienced reduction in PHN pain. CGIC: Total improved higher in treatment group than control group. 38% of treatment group versus 20% of the patients experienced reduction in PHN pain. Adverse reaction: There were no serious adverse effects observed or reported during trial. Only burning, stinging and erythema at application sites was directly attributable to capsaicin cream. Patients with PHN for more than 12 months Visual analog pain scale: Mean reduction is slightly higher in treatment group (15%) than control group (5.2%). PGIC: Total improved higher in treatment group than control group. 39% of treatment group versus 6% of the patients experienced reduction in PHN pain. CGIC: Total improved higher in treatment group than control group. 64% of treatment group versus 25% of the patients experienced reduction in PHN pain.	Capsaicin cream is a safe and effective treatment for the pain of PHN and should be considered for initial management of patients with this condition.
	Adverse reaction: There were no serious adverse effects observed or reported during trial. Only burning, stinging and erythema at application sites was directly attributable to capsaicin cream.
Bernstein et al., 1989	Visual analog pain scale for pain measurement: Mean reduction is higher in treatment group (30%) than control group (1% increase). Visual analog pain scale for pain relief: Mean reduction is higher in treatment group (54%) than control group (6%). PGIC: Total improved (much and very much improved) higher in treatment group (46%) than control group (6%). CGIC: Total improved higher in treatment group (77%) than control group (31%). Adverse reaction: There are mild to moderate skin reactions at application site. No systemic adverse events are caused by intervention.	Capsaicin could be used for initial treatment of postherpetic neuralgia due to low systemic toxicity and no drug interactions.