Abstract Post-infectious olfactory dysfunction (PIOD) is common in COVID-19 patients. This two-arm double-blinded randomised controlled trial aimed to establish proof-of-concept for Vitamin A versus placebo as a treatment modality for patients with PIOD. This study compared 9000 IU daily self-administered vitamin A intranasal drops versus peanut oil drops over 12 weeks in COVID-19 patients with PIOD. Outcome measures included: olfactory bulb volume (OBV), olfactory sulcus depth, cerebral functional MRI Blood Oxygen Level Dependent (BOLD) signal, Sniffin’ Sticks TDI score, SSParoT, Olfactory Disorder Questionnaire (ODQ) score and Brain Derived Neurotropic Factor (BDNF) levels were collected from participants at baseline and after trial intervention at 12 weeks. Fifty-seven PIOD were recruited in the trial and allocated to Vitamin A or placebo arm at a 2:1 ratio. After withdrawals and exclusions, 30 participants in the Vitamin A arm and 15 in the placebo arm were analysed. There was no significant difference in the change in OBV between both groups. Aside from an improvement in quality-of-life component of ODQ questionnaire scores (p = 0.01), there were no significant differences in any of the other secondary outcome measures. This proof-of-concept trial has demonstrated no significant effect of intranasal Vitamin A on olfactory function in COVID-19 PIOD patients. Further work is required to identify other therapeutic agents in the management of PIOD or evaluate a different PIOD cohort with non-COVID aetiology.
Yeap et al. (Sun,) studied this question.