A nurse is reinforcing teaching about phenytoin with a client who had a tonic-clonic seizure. Which of the following information should the nurse include in the teaching?

D. The INR is the standard laboratory test used to monitor the effectiveness of warfarin therapy. Warfarin interferes with the synthesis of vitamin K-dependent clotting factors, primarily factors II, VII, IX, and X. The INR provides a standardized measure of coagulation status, allowing healthcare providers to adjust warfarin dosage to maintain therapeutic anticoagulation while minimizing the risk of bleeding or thrombosis.
A. Platelets are involved in the process of blood clotting, but checking platelet levels is not specific to monitoring warfarin therapy. Platelet count may be relevant in assessing overall coagulation status, but it is not the primary laboratory value monitored for warfarin therapy.
B. OPTT measures the time it takes for blood to clot after specific clotting factors are activated. While OPTT is used to monitor the effectiveness of heparin therapy, it is not routinely monitored for warfarin therapy. Warfarin primarily affects the extrinsic pathway of the coagulation cascade, and the international normalized ratio (INR) is the standard laboratory test used to monitor warfarin therapy.
C. White blood cell count assesses the number of white blood cells in the blood and is used to evaluate the immune system and detect infections. Monitoring white blood cell count is not specific to warfarin therapy and is not routinely checked prior to administering warfarin.

B. Hemoglobin levels should be monitored regularly to assess the effectiveness of epoetin alfa therapy. Epoetin alfa stimulates the production of red blood cells, which should result in an increase in hemoglobin levels over time in clients with anemia. Monitoring hemoglobin levels helps determine if the medication is achieving the desired therapeutic effect.

A. Thrombin time measures the time it takes for a clot to form in a blood sample after thrombin is added. It is primarily used to assess abnormalities in the conversion of fibrinogen to fibrin during the clotting process. Thrombin time is not typically monitored to assess the effectiveness of epoetin alfa.
C. AST is an enzyme found primarily in the liver and heart. Elevated AST levels may indicate liver or heart damage but are not specifically related to the effectiveness of epoetin alfa therapy. AST is not routinely monitored to assess the effectiveness of epoetin alfa.
D. Troponin is a cardiac biomarker used to diagnose myocardial infarction (heart attack). Elevated troponin levels indicate damage to the heart muscle. Troponin levels are not directly related to the effectiveness of epoetin alfa therapy and are not routinely monitored for this purpose.