Chinese herbal medicine for constipation: zheng-based associations among herbs, formulae, proprietary medicines, and herb–drug interactions

Background As current symptomatic treatments of constipation are still unsatisfactory, an increasing number of patients seek help from Chinese medicine (CM), particularly Chinese herbal medicine (CHM). This study aimed to review the most frequently used CHM herbs and formulae, proprietary CHMs, and herb–drug interactions for functional constipation using zheng (syndrome)-based differentiation, and to determine the current practice of zheng-based CHM treatments for functional constipation.