Herb-immunosuppressive drug interactions: Implications for kidney transplant recipients

Advancements in immunosuppressive therapy have significantly improved long-term graft survival in kidney transplant recipients. Concurrently, the global use of medicinal plants and herbal medicines as complementary and alternative therapies has expanded, with many patients seeking to mitigate adverse effects and enhance their overall well-being. However, the simultaneous use of medicinal plants or herbal medicines alongside conventional immunosuppressive regimens presents significant clinical challenges due to the potential for pharmacokinetic and pharmacodynamic interactions. Many of these natural alternatives contain bioactive compounds that may modulate the metabolism and efficacy of immunosuppressants, either by enhancing or diminishing their therapeutic effects. This modulation often occurs through the induction or inhibition of hepatic cytochrome P450 enzymes and drug transporters, leading to fluctuations in immunosuppressant blood concentrations. Such variations can predispose transplant recipients to graft rejection due to subtherapeutic drug levels or, conversely, to toxicity from supratherapeutic exposure. Beyond pharmacological interactions, contamination of herbal preparations with heavy metals poses an additional risk. Exposure to nephrotoxic metals has been linked to graft dysfunction and an increased risk of graft loss. This narrative review critically examines the current scientific evidence regarding the interactions between medicinal plants and/or herbal medicines and immunosuppressive therapies, highlighting the potential implications for kidney transplant recipients. Also, it discusses the impact on graft survival, patient safety, and the need for greater regulatory oversight in the use of herbal medicines among this vulnerable population.