apfcbAPFCB eNewscoAPFCB News Volume 3, Issue 2MultidisciplinaryEnglishJul-Dec, 2024NNY2024091ArticlesCase-1: Preanalytical Challenges in Tacrolimus MonitoringEnglishY8284Dr. VivekPant1EnglishNDr. SantoshPradhan2EnglishY10.62772/APFCB-News.2024.2.3A 37-year-old woman experienced a significant increase in blood tacrolimus levels after starting Clarithromycin for an H. Pylori infection. Tacrolimus, used in organ transplant patients, has a narrow therapeutic index requiring close monitoring. The concurrent use of Clarithromycin, a CYP3A4 inhibitor, led to a dramatic spike in tacrolimus levels, causing signs of potential toxicity, such as elevated serum creatinine. This case highlights the critical importance of awareness of drug-drug interactions, especially involving CYP3A4 inhibitors, to prevent adverse effects and ensure patient safety. Clinicians should closely monitor tacrolimus levels when prescribing such medications.EnglishCYP3A4; Tacrolimus; Clarithromycin; Drug Interactionhttps://apfcb.org/APFCB_News/abstract?id=16References16191. Wolter K, Wagner K, Philipp T, Fritschka E. Interaction between FK 506 and clarithromycin in a renal transplant patient. European journal of clinical pharmacology. 1994 Sep; 47:207-8. 2. Bentata Y. Tacrolimus: 20 years of use in adult kidney transplantation. What we should know about its nephrotoxicity. Artificial organs. 2020 Feb; 44(2):140-52. 3. Yang Y, Huang X, Shi Y, Yang R, Shi H, Yang X, Hao G, Zheng Y, Wang J, Su L, Li Y. CYP3A5 genotype-dependent drug-drug interaction between tacrolimus and nifedipine in Chinese renal transplant patients. Frontiers in Pharmacology. 2021 Jul 5;12:692922. 4. Van Gelder T. Drug interactions with tacrolimus. Drug safety. 2002 Aug;25:707-12. 5. Baxter K, Baxter P, Claire, L. Immunosuppressant monograph: Stockleyand;rsquo;s drug interactions 10th ed. 2013