Interventions to improve anticoagulation with warfarin.

Area of Science:

• Pharmacology
• Clinical Pharmacy
• Internal Medicine

Background:

• Warfarin therapy is associated with significant potential drug-drug interactions (pDDIs).
• Minimizing pDDIs is essential for ensuring therapeutic efficacy and patient safety.
• Assessing the impact of pharmaceutical interventions on warfarin management is critical.

Purpose of the Study:

• To investigate pDDIs with warfarin in hospitalized patients.
• To evaluate the acceptance of pharmaceutical interventions by the medical team.
• To determine the effect of pDDIs and interventions on international normalized ratio (INR) outcomes.

Main Methods:

• Prospective study of inpatients initiating warfarin therapy at a Brazilian university hospital.
• Identification of pDDIs using the Drug-Reax program within Micromedex Healthcare Series 1.0.
• Monitoring of INR results and documentation of pharmaceutical intervention acceptance or rejection.

Main Results:

• 202 inpatients were studied, with an average of 10 drugs prescribed per patient.
• Each patient experienced at least one major or moderate pDDI with warfarin (mean = 3.6).
• Common interactions increasing anticoagulation included enoxaparin, simvastatin, omeprazole, and tramadol. Intervention rejection (15.8%) was linked to higher risk of abnormal INR (>5).
• Age, length of stay, number of pDDIs, and refusal of recommendations independently predicted INR > 5, increasing bleeding risk.

Conclusions:

• Major and moderate pDDIs with warfarin are highly prevalent in hospitalized patients.
• These interactions frequently lead to international normalized ratio (INR) values outside the desired therapeutic range.
• Pharmaceutical interventions, including physician education on managing drug interactions, can enhance patient safety during warfarin therapy.