• Neurology · Sep 2013

    Effect of chlorzoxazone in patients with downbeat nystagmus: a pilot trial.

    • Katharina Feil, Jens Claaßen, Stanislavs Bardins, Julian Teufel, Siegbert Krafczyk, Erich Schneider, Roman Schniepp, Klaus Jahn, Roger Kalla, and Michael Strupp.
    • From the Department of Neurology and German Center for Vertigo and Balance Disorders, University Hospital Munich, Campus Grosshadern, Munich, Germany.
    • Neurology. 2013 Sep 24; 81 (13): 1152-8.

    ObjectiveDownbeat nystagmus (DBN) is the most frequent form of acquired persisting fixation nystagmus with different symptoms such as unsteadiness of gait, postural instability, and blurred vision with reduced visual acuity (VA) and oscillopsia. However, different symptomatic therapeutic principles are required, such as 3,4-diaminopyridine and 4-aminopyridine, that effectively suppress DBN. Chlorzoxazone (CHZ) is a nonselective activator of small conductance calcium-activated potassium (SK) channels that modifies the activity of cerebellar Purkinje cells. We evaluated the effects of this agent on DBN in an observational proof-of-concept pilot study.MethodsTen patients received CHZ 500 mg 3 times a day for 1 or 2 weeks. Slow-phase velocity of DBN, VA, postural sway, and the drug's side effects were evaluated. Recordings were conducted at baseline, 90 minutes after first administration, and after 1 or 2 weeks.ResultsMean slow-phase velocity significantly decreased from a baseline of 2.74°/s ± 2.00 to 2.29°/s ± 2.12 (mean ± SD) 90 minutes after first administration and to 2.04°/s ± 2.24 (p < 0.001; post hoc both p = 0.024) after long-term treatment. VA significantly increased and postural sway in posturography showed a tendency to decrease on medication. Fifty percent of patients did not report any side effects. The most common reported side effect was abdominal discomfort and dizziness.ConclusionsThe treatment with the SK-channel activator CHZ is a potentially new therapeutic agent for the symptomatic treatment of DBN.Classification Of EvidenceThis study provides Class IV evidence that CHZ 500 mg 3 times a day may improve eye movements and visual fixation in patients with DBN.

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