Effect of Deuterated Drugs on Safety: Insights from Pharmacovigilance Data Analysis

Huntington's disease (HD) is a progressive neurodegenerative disorder characterized by motor, cognitive, and psychiatric symptoms. Tetrabenazine (TBZ), a vesicular monoamine transporter 2 inhibitor, is commonly used to manage chorea; however, it may exhibit fluctuating plasma levels and elicit frequent adverse events. In this study, we aimed to clarify the effects of TBZ deuteration on its safety profile. We compared the safety profiles of TBZ and deutetrabenazine (DTBZ) in real-world clinical practice using disproportionality analysis and the large-scale pharmacovigilance database, VigiBase-the WHO's global database of adverse drug reactions. Adverse event signals were assessed using the information component (IC). Seriousness was classified according to clinical outcome, and time to onset (TTO) was analyzed for selected events. TBZ showed signals for disorientation, dystonia, and sleep disorders (IC₀₂₅ > 0), whereas DTBZ did not. Serious adverse events were reported in 54.7% of TBZ cases and 37.9% of DTBZ cases. The TTO of sleep disorder was also evaluated; however, the number of cases with available TTO information was limited. DTBZ showed fewer adverse event signals and a lower proportion of serious adverse events than TBZ. These findings suggest potential differences in the safety profiles of the two drugs, which may influence tolerability in the treatment of HD.