Kikyo-to vs. Placebo on Sore Throat Associated with Acute Upper Respiratory Tract Infection: A Randomized Controlled Trial

OBJECTIVE: Kikyo-to (KKT) is a fixed combination of glycyrrhiza root and platycodon root extracts. It is an herbal medicine traditionally used in Japan for relieving sore throat associated with acute upper respiratory tract infection (URTI). No controlled studies have yet demonstrated its effect, however. We investigated the efficacy of KKT on sore throat associated with acute URTI. METHODS: Patients with sore throat who were diagnosed with URTI at the General Medicine Department Office, Akashi Medical Center Hospital, between December 2017 and May 2018 were enrolled. Participants were randomly assigned to two groups at a 1:1 ratio, with stratification by age and sore throat score on a Visual Analogue Scale (VAS), to receive 2.5 g of either KKT or a placebo. Participants and investigators were blinded to group allocation. The primary outcome was the change in sore throat score on VAS 10 minutes after KKT administration. Secondary outcomes were the impact of the sore throat on daily life (none, mild, moderate, and severe) at 10 minutes after administration. RESULTS: Thirty-five participants were assigned to each group (n=70, total). The difference in the mean change of sore throat score according to VAS within 10 minutes between the two groups was not statistically significant (KKT 14.40 vs. placebo 17.00; p=0.39). The proportion of patients with a moderate or greater impact of their sore throat on their daily life was also not significantly different between the groups (KKT 22.9% vs. placebo 40.0%; p=0.20). Patients reported no side effects. CONCLUSION: KKT did not significantly relieve sore throat associated with acute URTI compared with placebo.