Table 4.

Placebo response of trials of duloxetine, venlafaxine, glyceryl trinitrate/sodium valproate and cannabinoids.

Trial	Drug	Number in placebo group	Length of trial(weeks)	Percentage change from baseline of pain scores	Percentage of placebo responders
Goldstein et al. [2005]	Duloxetine	115	12	33%	26% (50% pain improvement)
Raskin et al. [2006]	Duloxetine	116	12	29%	30% (50% pain improvement)
Wernicke et al. [2006]	Duloxetine	108	12	24%	27% (50% pain improvement)
Rowbotham et al. [2004]	Venlafaxine	81	6	27%	34% (50% pain improvement)
Selvarajah et al. [2009]	Sativex	14	12	37%	64% (30% pain improvement)
Agrawal et al. [2009]	Sodium valproate + GTN	GTN + placebo = 20	12	36%	n/a
		Placebo + Sodium valproate = 20		23%
		Placebo + placebo = 21		6%