The effectiveness of zinc replacement therapy is reported to be approximately 70％. However, the effectiveness of this therapy in our department has been lower than that reported in the field of otolaryngology. In the present study, we examined the effectiveness of zinc replacement therapy in patients with taste disorder. Forty patients were administered only zinc formulations（Polaprezinc, 150mg/day） for ≥8 weeks. The time until effect, serum zinc level and other parameters were used to evaluate improvement in the taste disorder. In the present study, three cut-off values were determined based on the serum zinc levels.
The overall improvement rate among the patients in this study was 50％. The improvement rates by serum zinc level were 57％ at ＜60μg/dl, 56％ at 60-69μg/dl, 60％ at 70-79μg/dl, and 14％ at ≥80μg/dl. There was a significant difference in the improvement rate between the patient groups with serum zinc levels of ＜80 and ≥80μg/dl（57％ vs. 14％, p＜0.05）. The times until effective expression in the 20 subjects with improvement were less than 2 months in 20％ and more than 2 months in 80％, with significant differences among the two groups（p＜0.05）. Polaprezinc was effective in 60％ of the cases where serum zinc level measured in blood tests was less than 80μg/dl. Effectiveness was not observed when the serum zinc level was more than 80μg/dl. Therefore, zinc supplementation therapy should be conducted over the long term after proper selection of the patients.
