The effects of different drugs on caloric test and slow-phase velocity of nystagmus

Objectives: Nystagmus is the only objective evidence of vertigo which is a subjective complaint. The aim of this study is to determine the effects of betahistine and dimenhydrinate on the slow-phase velocity of nystagmus at caloric test and on the subjective vertigo scale.Materials and Methods: Forty volunteered patients who were consultated to our clinic for vertigo between December 2009 and January 2012 were included in this study. Patients were divided into two groups as betahistine and dimenhydrinate groups. Patients in first group were administered betahistine at 3x24mg dosage. During this treatment caloric test was performed and dosage was risen to 3x48mg at patients because of ongoing complaints, than caloric test was repeated. Caloric test was also performed at patients in second group during and after the treatment of dimenhydrinate. Patients in both groups were asked to degree their subjective vertigo complaint between 1 and 5. Slow-phase velocity of nystagmus at caloric test and subjective vertigo complaint were evaluated.Results: Averages of slow-phase velocity at first group were 19,3 and 23,2,1 degrees/second at 3x24mg and 3x48mg betahistine dosage respectively. At second group, averages of slow-phase velocity were 13,4 and 18,2 degrees/second during and after the treatment of dimenhydrinate respectively. Subjective vertigo scores were decreased with dimenhydrinate and raised with the dosage of betahistine. Subjective vertigo scores and slow-phase velocities were corelated at most of the patients.Conclusion: Slow-phase velocity of nystagmus was augmented with use of betahistine and this effect was promoted with increase of dosage. Dimenhydrinate prevents vertigo with supressing vestibular system and causing sedation. Whereas betahistine activates vestibular system and increases awareness. In conclusion these two drugs should not be used together because of their opposite effects on vestibular system. Dimenhydrinate should be used at acute attacks of vertigo, whereas betahistine should be preferred at the period between the attacks.Keywords: Vertigo, nystagmus, slow-phase of velocity, dimenhydrinate, betahistin