Successful Management of Anticoagulation Therapy During International Travel

Warfarin is considered a high-risk drug because of its narrow therapeutic window, variability in dose response, and multitude of drug and food interactions. Although travel advice is available for patients who are taking warfarin, it is geared toward patients who are traveling to developed countries and tends to be lacking in detail. We describe a 53-year-old woman with two mechanical heart valves and chronic atrial fibrillation who was taking warfarin for thromboembolism prophylaxis and had plans to travel to Vietnam for 10 weeks. Three days before her departure, she was prescribed amiodarone for long-term use. As a result of the extended duration of her travel and the complexities of warfarin use, the pharmacists who managed the patient's anticoagulation reviewed several aspects of a comprehensive management approach with the patient for a safe international trip. They assessed the patient's thromboembolic and hemorrhagic risks, and determined which other drugs (e. g., enoxaparin, phytonadione), dosages, and adequate supplies would be required along with warfarin, as well as how to safely transport these drugs during travel. In addition, the logistics of effectively monitoring international normalized ratio (INR) levels were evaluated, and methods of managing multiple potential scenarios were carefully planned out. Contact with the patient was made through pharmacist-directed telephone visits throughout the travel period. A total of 12 telephone visits were conducted with the patient during the 10 weeks of travel. Her INR was supratherapeutic on three occasions and was subtherapeutic once; however, neither enoxaparin nor phytonadione were needed during the travel period, and the patient returned safely to the United States. Effective and safe use of high-risk drugs for patients leaving the United States requires extensive pretravel planning, and pharmacists can play a central role in optimizing therapeutic outcomes for these patients during international travel.