THE CALL: A hospital-affiliated cardiologist calls the Anticoagulation Center to enroll a new patient who takes dabigatran and needs "monitoring" because of possible noncompliance with therapy.

THE CASE: The patient in question is a 45 year old male with recent onset atrial fibrillation. He is obese, with hypertension, diabetes and hyperlipidemia. He has a history of medication nonadherence, despite multiple attempts to set up reminder systems for medication administration.

THE PROBLEM: Each of the new oral anticoagulants was designed to be given at a fixed dose without the need for dosing adjustments based on routine coagulation studies. Dabigatran, a direct thrombin inhibitor, increases the ecarin clotting time, thrombin time, and prothrombin time/INR is a linear fashion with increasing drug concentrations. Activated partial thromboplastin time also increases, but with a non-linear response above certain drug concentrations.

However, the changes in these coagulation labs that occur in response to therapeutic doses of dabigatran are not broad enough to define a "therapeutic range" or to quantify the degree of anticoagulation.   In addition, after ingesting a dose of dabigatran, a maximum serum concentration will occur in the first several hours, and then decline to a minimum serum concentration. These "peaks" and "troughs" will yield different values for relevant lab tests as well. 

Although relevant coagulation studies may be useful to determine the presence (or absence) of dabigatran, they are not able to quantify the degree of anticoagulation, and will change over the dose interval as the drug is absorbed and then cleared.   

THE SOLUTION: This patient will not benefit from monitoring or measuring coagulation studies. However, the Anticoagulation Clinic staff may be able to assist in educating him about the signs and symptoms of stroke as well as the risks and clinical presentation of bleeding. He will benefit from adherence coaching, motivational systems for medication administration, and other direct care assistance. While these activities may not be considered traditional Anticoagulation Clinic responsibilities, they are an important niche for specialists in thrombosis in an era of changes in anticoagulant therapy.