A nurse is preparing to administer erythromycin PO to a client who has an infection. The nurse checks the client's medical record and notes that the client has a severe allergy to penicillin. Which of the following actions should the nurse take?

B. Headache, particularly a pounding headache or throbbing sensation, is a well-known side effect of nitroglycerin use. It occurs due to the vasodilatory effects of nitroglycerin, which can lead to dilation of blood vessels in the head and neck.
A. Ringing in the ears, also known as tinnitus, is not a common adverse effect of nitroglycerin. Tinnitus is typically associated with certain medications, exposure to loud noises, or underlying medical conditions such as inner ear disorders. It is not a recognized adverse effect of nitroglycerin.
C. Nitroglycerin is not known to increase blood pressure. In fact, it typically causes vasodilation and can lead to a decrease in blood pressure, especially when used sublingually or transdermally. Hypotension, rather than hypertension, is a potential adverse effect of nitroglycerin therapy.

D. Polyuria, or excessive urination, is not a recognized adverse effect of nitroglycerin. Polyuria may occur as a result of other medications or underlying medical conditions affecting renal function, but it is not directly associated with nitroglycerin use.

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.