Clinical evaluation of liquid placebos for an herbal supplement, STW5, in healthy volunteers

Background: Although clinical trials are needed to evaluate the efficacy of liquid herbal medicinal products, design of feasible placebos that mimic the appearance, taste, and smell of such products is particularly challenging. Objective: The design and feasibility of a liquid placebo for STW5, an herbal medicinal product used for various gastrointestinal problems, was explored in this study. Design: Four sample products-STW5, a fresh and aged version of a placebo made from a seasoning mix (Maggi™), and a placebo with aged artificial flavor and food coloring-were compared in two organoleptic (sensory), single-blind trials with a total of 60 (N=60) healthy volunteers (n₁=30, n₂=30). Measurements: The appearance, smell, and taste of each solution were evaluated using a Likert scale questionnaire. Results: The liquid placebos evaluated were similar in regard to appearance, smell, and taste. However, participants indicated that for a clinical trial with STW5, the aged Maggi™ placebo would be more viable compared to the fresh Maggi placebo or the aged artificial food coloring placebo with licorice flavor. Participants also noted that the mint flavor and smell of STW5 was distinctly different from the placebo solutions. Limitations: The trials were conducted in healthy volunteers, not in actual patients. Conclusions: The aged Maggi™ liquid mix may be more favorable as a placebo than the artificially created one. However, further adjustment will need to be made to the Maggi™ placebo to simulate the complex aromatic composition of STW5 for clinical studies in the future.