The Role of the Pharmacist in a Patient's Care for Individuals Undergoing Anticoagulant Therapy: A Case Report.

Achieving clinical effectiveness with vitamin K antagonists (VKAs) requires a Time in Therapeutic Range (TTR) above 65%. TTR is influenced by genetics (CYP2C9, VKORC1, CYP4F2), treatment adherence, and knowledge. The SAMe-TT2R2 algorithm is used to assess VKA treatment suitability. In this case report, SAMe-TT2R2 and pharmacogenetic analysis were used to improve oral anticoagulant management in a patient with poor control of INR. An 84-year-old, obese male with atrial fibrillation, undergoing acenocoumarol therapy, had a suboptimal TTR. An assessment with the SAMe-TT2R2 algorithm indicated a favorable profile for VKA use. An educational intervention on vitamin K-rich foods was conducted, and his physician was informed about the interaction between omeprazole and acenocoumarol, recommending its replacement with pantoprazole. This intervention was accepted by the physician and, three months post-intervention, the patient's TTR improved to 100%. Poor adherence and limited knowledge contributed to treatment failures in patients with a good VKA profile. Pharmaceutical interventions significantly improved TTR management. Patients with favorable genetic and clinical profiles could achieve adequate control of their anticoagulant medication through these interventions. Predictive tools may help select patients who can effectively and safely use VKAs through pharmaceutical interventions.

Importance of Pharmacogenetics and Drug-Drug Interactions in a Kidney Transplanted Patient.

Tacrolimus (TAC) is a narrow-therapeutic-range immunosuppressant drug used after organ transplantation. A therapeutic failure is possible if drug levels are not within the therapeutic range after the first year of treatment. Pharmacogenetic variants and drug-drug interactions (DDIs) are involved. We describe a patient case of a young man (16 years old) with a renal transplant receiving therapy including TAC, mycophenolic acid (MFA), prednisone and omeprazole for prophylaxis of gastric and duodenal ulceration. The patient showed great fluctuation in TAC blood concentration/oral dose ratio, as well as pharmacotherapy adverse effects (AEs) and frequent diarrhea episodes. Additionally, decreased kidney function was found. A pharmacotherapeutic follow-up, including pharmacogenetic analysis, was carried out. The selection of the genes studied was based on the previous literature (CYP3A5, CYP3A4, POR, ABCB1, PXR and CYP2C19). A drug interaction with omeprazole was reported and the nephrologist switched to rabeprazole. A lower TAC concentration/dose ratio was achieved, and the patient's condition improved. In addition, the TTT haplotype of ATP Binding Cassette Subfamily B member 1 (ABCB1) and Pregnane X Receptor (PXR) gene variants seemed to affect TAC pharmacotherapy in the studied patient and could explain the occurrence of long-term adverse effects post-transplantation. These findings suggest that polymorphic variants and co-treatments must be considered in order to achieve the effectiveness of the immunosuppressive therapy with TAC, especially when polymedicated patients are involved. Moreover, pharmacogenetics could influence the drug concentration at the cellular level, both in lymphocyte and in renal tissue, and should be explored in future studies.