The Safety of Multiple-Dose Liquid Blend Containing Kava and Kratom in Healthy Adults

Abstract

This study investigates the safety of three different daily dosages of a liquid blend containing kava and kratom (Feel Free® Classic Tonic {FFCT}) in healthy adults over six consecutive days of supplementation. Both kava and kratom have been used traditionally for hundreds of years, but there is limited data on the combined safety of these ingredients. In this randomized, double-blind, placebo-controlled trial, the participants were assigned to receive one of three daily dosages of FFCT or placebo. Safety assessments included the monitoring of vital signs, clinical chemistry, hematology, and withdrawal symptoms using the Clinical Opiate Withdrawal Scale (COWS) and the Subjective Opiate Withdrawal Scale (SOWS). The results indicate that FFCT was safe, with mild to moderate adverse events (AEs) such as nausea, headaches, and fatigue, particularly in the high-dosage (HD) group. No significant changes in liver or kidney function were noted, and all vital signs remained within normal physiological ranges although some statistically significant changes in blood pressure (BP) and respiratory rate (RR) were observed. There were no clinically significant observations in COWS or SOWS scores despite a small but statistically significant increase in COWS total score in the high-dose group on day 7. Overall, FFCT appears safe for short-term use in healthy adults, with no significant impact on vital signs, laboratory values, or withdrawal symptoms.