Table 1. Characteristics of included studies.

Study	Age, y, mean (range)	Type of study	Location	Patients	Num	Type of outcome	Control group or arm	Medicine dose/day	Therapy duration	Side effects
Ryan 2012	61–63	Randomized double-blind placebo-controlled	Australia	refractory chronic cough	62 (52 completed)	+clinical improvement in LCQ score =20:12 mean VAS score (cm) =36:42	Placebo (n=26)	Gabapentin in maximum tolerable of 1,800 mg (n=26)	12 weeks	Nausea, stomach pain, fatigue, dizziness, dry mouth
Jeyakumar 2006	55	Randomized	USA	chronic cough resulting from postviral vagal neuropathy	28	# Patients’ subjective cough responses: complete response =11:0 partial response =3:3 no response =1:10 QOL data correlated strongly with the patients’ subjective responses	Codeine/guaifenesin (n=13)	Amitriptyline 10 mg qn (n=15)	10 days	No
Dicpinigaitis 1998	37–69	Randomized double-blind placebo-controlled, cross-over	USA	refractory cough	2	Cough episodes per 24 hours by diaries documenting 2:0	Placebo (n=2)	Baclofen 10 mg tid (n=2)	28 days	No

^#, those patients experiencing a 75% to 100% cough reduction were recorded as having a complete response, 25% to 50% a partial response, and 0% as having no response; LCQ, Leicester cough questionnaire; QOL, quality-of-life; ⁺, a clinical improvement in LCQ score of greater than 1∙3 the smallest change in score regarded as clinically meaningful; VAS, visual analogue scale.