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OBJECTIVE	To investigate the characteristics of residual symptoms and to evaluate the effects of adjuvant vestibular suppressants on residual symptoms after successful canalith repositioning procedures ( CRPs ) .
METHODS	Individual randomized controlled trial .
METHODS	One hundred fifty patients with idiopathic benign paroxysmal positional vertigo who achieved successful CRPs on initial visit participated in this study .
METHODS	Dizziness Handicap Inventory ( DHI ) questionnaires were completed before CRPs .
METHODS	All study populations were divided into three groups after successful CRPs on the initial visit day : the medication ( V ) group ( treated with a vestibular suppressant [ dimenhydrinate 50 mg per day ] ) , the placebo ( P ) group , and the no medication ( N ) group .
METHODS	One week after successful CRPs , residual symptoms were checked and repeated DHI questionnaires were completed to compare residual symptoms .
RESULTS	Among the 138 patients who did not show positional nystagmus at follow-up , 67 ( 48.5 % ) complained of residual symptoms .
RESULTS	The presence of residual symptoms was more prevalent in the P and N group compared with the V group ( P = .035 , P = .017 , respectively ) .
RESULTS	The most frequent residual symptom was lightheadedness ( n = 42 ) .
RESULTS	Moreover , in the V group , lightheadedness was significantly reduced compared with the P group ( P = .029 ) .
RESULTS	However , in the analysis of DHI , total and subscale scores did not differ across the three groups before or after successful CRP .
CONCLUSIONS	Vestibular suppressants significantly reduced residual symptoms compared to both placebo and no medication after CRP .
CONCLUSIONS	However , there was no significant reduction in DHI score compared with the control group , suggesting that the residual symptoms could not be evaluated by DHI score alone .

