A nurse on an oncology unit is preparing to administer doxorubicin to a client who has breast cancer. Prior to beginning the infusion, the nurse verifies the client's current cumulative lifetime dose of the medication. For which of the following reasons is this verification necessary?

Choice A reason: This is incorrect because extravasation is not related to the lifetime cumulative dose limit of doxorubicin, but to the leakage of the medication from the vein into the surrounding tissue. Extravasation can cause severe tissue damage and necrosis, and should be prevented by using a central venous catheter and monitoring the infusion site.

Choice B reason: This is incorrect because red tinged urine and sweat are not related to the lifetime cumulative dose limit of doxorubicin, but to the normal excretion of the medication from the body. Red tinged urine and sweat are expected side effects of doxorubicin and do not indicate toxicity or harm.

Choice C reason: This is correct because an excess amount of doxorubicin can lead to cardiomyopathy, which is a serious and potentially fatal complication of the medication. Cardiomyopathy is a condition in which the heart muscle becomes weak and unable to pump blood effectively. The risk of cardiomyopathy increases with the cumulative lifetime dose of doxorubicin, which should not exceed 450 to 550 mg/m2.

Choice D reason: This is incorrect because myelosuppression is not related to the lifetime cumulative dose limit of doxorubicin, but to the dose-dependent effect of the medication on the bone marrow. Myelosuppression is a condition in which the production of blood cells is reduced, leading to anemia, leukopenia, and thrombocytopenia. Myelosuppression can be managed by adjusting the dose and frequency of doxorubicin and monitoring the blood counts.

Choice A reason: Atropine is not the correct answer, as it is an anticholinergic medication that is used to treat bradycardia, not warfarin overdose. Atropine has no effect on the INR or the coagulation cascade.

Choice B reason: Epinephrine is not the correct answer, as it is a catecholamine medication that is used to treat anaphylaxis, cardiac arrest, or severe hypotension, not warfarin overdose. Epinephrine has no effect on the INR or the coagulation cascade.

Choice C reason: Vitamin K is the correct answer, as it is the antidote for warfarin overdose. Vitamin K is a fat-soluble vitamin that is essential for the synthesis of clotting factors II, VII, IX, and X. Vitamin K can reverse the effects of warfarin and lower the INR to a therapeutic range.

Choice D reason: Protamine is not the correct answer, as it is the antidote for heparin overdose, not warfarin overdose. Protamine is a protein that binds to and neutralizes heparin, but has no effect on warfarin or the INR.