Synergy arises when the combined effect of multiple agents exceeds the sum of their individual activities. Pharmacological and bioactive chemical synergy offers a promising approach to enhance therapeutic efficacy, reduce toxicity, and overcome drug resistance. This review explores the mechanisms underlying drug synergy, focusing on pharmacodynamic and pharmacokinetic interactions, enhanced efficacy, and potential toxicity risks. It also highlights key gaps, challenges, and future research directions. This review integrates published findings on bioactive–drug interactions, with emphasis on mechanistic pathways and therapeutic applications. Literature was retrieved using keywords on synergy and pharmacological interactions from databases including PubMed, Google Scholar, and Web of Science, last accessed on September 30, 2025, covering studies up to 2025. Evidence indicates that synergy occurs through complementary pharmacodynamic and pharmacokinetic mechanisms. Pharmacodynamic effects include multi-target modulation, receptor co-activation, and inhibition of resistance pathways, while pharmacokinetic mechanisms involve improved absorption, metabolism, and excretion. Natural sources such as plants, microbes, and marine organisms provide a rich reservoir of compounds capable of enhancing conventional treatments. Curcumin and epigallocatechin gallate have been shown to increase the efficacy of antibiotics and antifungals against resistant microorganisms. Berberine combined with metformin improves glucose regulation in metabolic disorders through overlapping mechanisms. Similarly, green tea catechins, resveratrol, and curcumin enhance chemotherapy effectiveness while reducing adverse effects in oncology. The integration of natural bioactive compounds with conventional drugs represents a powerful strategy for developing next-generation therapies. However, there are still limitations, including challenges with bioavailability, safety profiles, and consistency across studies. Future research should prioritize pharmacokinetic modeling, advanced delivery systems, and systems biology approaches to optimize bioactive–drug synergy and translate laboratory findings into effective clinical applications.
Akinwumi et al. (Sun,) studied this question.