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Open Access Oral Anticoagulant Therapy and International Normalized Ratios in Swine

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While monitoring coagulation testing in Yucatan miniature swine being given oral anticoagulants, we noticed instances of high international normalized ratios (INR) without clinical complications in our animal model. All pigs (n = 17) weighed approximately 35.2 kg and were dosed daily with 2 to 3 mg of coumadin. Plasma samples were obtained and assayed for prothrombin time (PT), calculated INR, and activated partial thromboplastin time (APTT) at baseline, and after 7 and 14 days of coumadin therapy. Results of initial testing indicated high INR values after anticoagulation and short APTT values at baseline, which led us to consider the activity of vitamin K-dependent coagulation factors in the pig. This information was not available in literature concerning this strain of swine, and was surprising given that pigs are frequently used cardiac research models. Using the same plasma samples, we repeated the PT, INR, and APTT determinations using different reagents and a different analyzer. We also determined activities of coagulation factors II, VII, IX, and X. Large PT and INR differences were seen between the two instrument/reagent combinations, possibly due to the differences in the thromboplastins used and differences in the photo-optic versus manual clotdetection method of the instruments. Vitamin K-dependent factors in all pigs responded to coumadin by decreasing to <30.0% activity, except for factor IX. The high INR values were not as pronounced when the second instrument/reagent combination was used, and the results seemed more in line with the animals' clinical condition. With this instrument/reagent combination, the pig can be considered a good model for research requiring oral anticoagulant medication.

Document Type: Research Article

Affiliations: 1: CLS/NCA, Clinical Investigation Director, Clinical Investigations HSRL, Wilford Hall Medical Center, 1255 Wilford Hall Loop, Lackland AFB, TX 78236-5319 2: 554th Medical Group, Nellis Air Force Base, Nevada 3: Clinical Investigations, Wilford Hall Medical Center, Lackland Air Force Base, Texas

Publication date: 1998-08-01

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  • Comparative Medicine (CM), an international journal of comparative and experimental medicine, is the leading English-language publication in the field and is ranked by the Science Citation Index in the upper third of all scientific journals. The mission of CM is to disseminate high-quality, peer-reviewed information that expands biomedical knowledge and promotes human and animal health through the study of laboratory animal disease, animal models of disease, and basic biologic mechanisms related to disease in people and animals.

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