Drug-Drug Interaction Between Fluconazole and Vancomycin: A Case Report

We present the case of a probable pharmacokinetic drug-drug interaction (DDI) between fluconazole (FLU) and vancomycin (VCM), in a patient who underwent hepatobiliary surgery, and biliary drainage, and was under treatment with vancomycin, meropenem, and fluconazole, due to infectious pathology. Changes in the kinetic process of VCM and FLU has not been fully elucidated. Therefore, understanding the changes in renal transporters involved in the renal excretion pathway of VCM and FLU (e.g. multidrug resistance-associated proteins, organic cation transporters, P-glycoprotein) is beneficial in predicting better drug disposition and optimize optimizing dosing. Inhibition of the aforementioned transporters is a common mechanism underlying DDIs. After pharmacokinetic monitoring of VCM treatment, the trough concentration values and the half-life of VCM showed an abnormally unexpected increase when VCM was used in combination with FLU, compared to data obtained when vancomycin was used without fluconazole. Said changes, of the pharmacokinetic parameters studied, would support a DDI between FLU and VCM. Because of this, special caution is required whenever VCM is co-administered with fluconazole, and close monitoring of VCM trough concentrations is recommended to minimize the risk of toxicity.

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