Intranasal vitamin A is beneficial in post-infectious olfactory loss.

Abstract

Vitamin A plays a decisive role in the regeneration of olfactory receptor neurons. In this retrospective study we investigated the effectiveness of topical vitamin A in patients with post-infectious and posttraumatic smell disorders. Retrospective cohort. A total of 170 patients (age range 18-70years, mean age 52years) participated. Forty-six patients were treated with smell training only. The remaining 124 patients received smell training and topical vitamin A. Olfactory function was assessed using the Sniffin' Sticks test kit, a validated technique to measure odor thresholds, discrimination and identification. The duration of olfactory training was 12weeks. In patients receiving vitamin A, this was applied topically (head back position) at a dose of 10,000IU/day for 8weeks. Follow-up testing was performed approximately 10months after the first assessment. Thirty-seven per cent of all post-infectious patients treated with vitamin A exhibited clinical improvement, whereas only 23% improved in controls. Using a Chi-square test, this was a significant result (χ 2=7.06, df=2, p=0.03). In addition, when comparing change in score after treatment, olfactory training+vitamin A produced significantly greater improvement compared with training alone, in discrimination score for all patients (1.4 points, p=0.008), and in threshold and discrimination in the post-infectious group (1.6 points, p=0.01 and 1.4 points, p=0.04, respectively). Intranasal vitamin A at a dose of 10,000IU per day for 2months may be useful in the treatment of post-infectious olfactory loss. Further work with prospective, placebo-controlled studies is required to confirm these findings.