Abstract
The issue of drug resistance and tolerance presents a significant challenge as it diminishes the efficacy and potency of medications, posing a formidable obstacle for physicians striving to enhance pharmacological therapy worldwide. These resistance mechanisms can arise from genetic predispositions or as a consequence of medical interventions. Notably, acquired resistance or tolerance may extend to other drugs within the same or different classes, despite differing mechanisms of action. This phenomenon leads to the ineffectiveness of various pharmacological treatments over time, hindering the attainment of complete remission for numerous illnesses spanning metabolic disorders, autoimmune diseases, carcinomas, infectious diseases, cardiovascular diseases, and neurological disorders. Vitamin D, an essential lipid-soluble nutrient crucial for regulating calcium and phosphorus levels, is emerging as a potential solution to counteract treatment resistance and tolerance in various conditions such as cancer, tuberculosis, and depression. This review scrutinizes existing research and offers insights for future investigations aimed at fully elucidating the therapeutic potential of vitamin D in mitigating the challenges associated with prolonged medication regimens and drug treatment failures. Trial Registration: ClinicalTrials.gov identifier: NCT01169259 and NCT04342598.