Background Dabigatran, an oral anticoagulant classified as a direct thrombin inhibitor, is used for the prevention of stroke and systemic embolism. However, it has limitations in its method of administration; dabigatran should not be removed from the capsule and administered through a tube because of its unstable bioavailability. Purpose To report a case that required dabigatran to be administered through a tube after removal from the capsule. Materials and MethodsA 79-year-old Japanese male with normal hepatic and renal function was receiving warfarin for the prevention of systemic embolism due to atrial fibrillation. When he started S-1 treatment as an adjuvant treatment for gastric cancer, PT- and INR levels exceeded the scale. Because this elevation was thought to be due to the interaction between warfarin and S-1, warfarin was replaced with dabigatran. After switching anticoagulants, PT-INR and aPTT stabilised. Subsequently, however, the patient fell and experienced paralysis due to medullary damage. We tried to administer dabigatran through a tube after removal from the capsule while carefully monitoring the blood levels. Although the typical daily dose of dabigatran is 220 mg, the daily dose in the present case was set to 150 mg in consideration of elevated blood concentration due to removal from the capsule. The dabigatran concentration 4 h after the first administration (peak) and before the second and third doses (trough) was measured by ultra-performance liquid chromatography/mass spectrometry. ResultsThe dabigatran concentration was 115.8, 62.45, and 80.05 ng/mL 4 h after the first administration and before the second and third doses, respectively, which is similar to data obtained in a clinical study using healthy Japanese volunteers. aPTT was 38–48 s. Conclusions We were able to administer dabigatran after removal from the capsule through a tube at two-thirds the regular dose and maintain a similar dabigatran blood concentration to that obtained in a clinical study through careful monitoring of dabigatran plasma levels. No conflict of interest.