Kikyo-to for Acute Upper Respiratory Tract Infection-Associated Sore Throat Pain: A Multicenter Randomized Controlled Trial.

Objectives: Kikyo-to (Kt), a herbal medicine composed of glycyrrhiza root (Chinese licorice) and Platycodon root extracts (Chinese bellflower), is commonly used in Japan for relief of throat symptoms related to acute upper respiratory tract infection (URTI). Its effectiveness on URTI-associated sore throat pain over 30 min is examined here in comparison with a placebo. Design: Randomized double-blinded multicenter trial. Settings/Location: Two local Japanese medical centers with primary care. Subjects: Patients aged 20-65 years with URTI-related sore throat. Interventions: Patients were randomized to receive either 2500 mg of Kt, or 2500 mg of placebo (lactose). Randomization was stratified by age (< 45 vs. ≥ 45 years) and baseline sore throat score according to visual analogue scale (VAS) (< 50 vs. ≥ 50). Outcome measures: Primary outcome was change to sore throat score according to VAS 30 min after administration of Kt. Perceived impact of the sore throat on daily life at 30 mins after administration was another outcome. Outcomes are analyzed in the intention-to-treat population. Results: Among 70 participants, (Kt group: 36; placebo group: 34), each group contained 34 patients for analysis (n = 68, total). Difference between the groups in the mean change of sore throat score according to VAS at 30 min was without statistical significance (Kt 15.3, placebo 17.2; p = 0.66). Patients reporting that their sore throat had a moderate or greater impact on daily life were also similar in proportion between the groups (Kt 61.8% vs. placebo 55.9%; p = 0.80). Side effects were not reported. Conclusions: Kt did not relieve acute URTI-associated sore throats significantly more than a placebo. (UMIN trial ID: UMIN000035591).