Objective: A phase IIb double-blind, placebo-controlled, cross-over, randomized clinical trial of a single dose of sodium oxybate investigated the efficacy and safety of the drug for the treatment of laryngeal dystonia (LD).

Background: Isolated focal LD is characterized by involuntary spasms in laryngeal muscles, predominantly affecting speech production and impairing daily vocal communication. Treatments targeting LD pathophysiology are non-existent.

Method: Based on a similar mechanism of action of sodium oxybate and alcohol, 106 patients were stratified into alcohol-responsive (EtOH+) and alcohol-non-responsive (EtOH-) groups and blindly randomized to a cross-over sequence of 1.5 g of sodium oxybate and a matching placebo. The primary outcome measure was a change in LD symptom 40 min after sodium oxybate intake compared to placebo.

Results: Sodium oxybate was found to be superior to placebo in reducing voice symptoms in EtOH+ but not EtOH- patients. A significant difference between drug and placebo effects was found starting with ≥ 16% symptom improvement in EtOH+ LD patients, with 64% of these patients benefiting by 40.8% benefits. All forms of LD benefited similarly, including those with adductor, abductor, or dystonic voice tremor. Efficacy gradually waned from 40 min to 300 min after intake. No significant changes in cognitive function, suicidality, or vital signs were observed related to drug administration. Mild transient side effects, including daytime sleepiness, dizziness, and nausea, were common.

Conclusion: Sodium oxybate provided significant and clinically meaningful improvement of voice symptoms in EtOH+ LD patients, with acceptable tolerability. Oral sodium oxybate offers the first, pathophysiologically relevant oral therapeutic option for LD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-phase-iib-double-blind-placebo-controlled-randomized-cross-over-clinical-trial-of-sodium-oxybate-in-isolated-focal-laryngeal-dystonia/