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: The extra letters after the name of the medication do not mean it is a stronger dose, but that it is a combination of two different medications. Metoprolol is a beta-blocker that lowers blood pressure and heart rate, while hydrochlorothiazide is a diuretic that reduces fluid retention and blood volume. The combination of these two medications may have a synergistic effect and lower blood pressure more effectively than either one alone.

Choice B reason: The client will have to do some things differently because it is not the same medication, but a combination of two medications. The client will have to monitor their blood pressure, weight, fluid intake, and electrolyte levels more closely, as the addition of hydrochlorothiazide may increase the risk of dehydration, hypotension, and hypokalemia. The client will also have to avoid alcohol, salt, and potassium supplements, as they may interact with the medication and affect its efficacy or safety.

Choice C reason: The client will still have to diet to lose weight, as the medication does not cause weight loss, but may cause weight gain due to fluid retention. The client will have to follow a healthy diet that is low in sodium, fat, and cholesterol, as these may worsen hypertension and increase the risk of cardiovascular complications. The client will also have to exercise regularly, as this may help lower blood pressure and improve overall health.

Choice D reason: The client may experience fewer side effects with the new medication, as the combination of metoprolol and hydrochlorothiazide may lower the dose and frequency of each medication, and reduce the adverse effects of each one. For example, metoprolol may cause fatigue, dizziness, or bradycardia, while hydrochlorothiazide may cause dry mouth, headache, or gout. The combination of these two medications may balance out these effects and improve the client's tolerance and compliance.

Choice A reason: A headache is not likely due to the anxiety about the chest pain, as anxiety usually causes other symptoms, such as palpitations, sweating, or trembling. A headache is more likely related to the vasodilating action of nitroglycerin, which causes increased blood flow to the brain.

Choice B reason: A headache does not indicate tolerance to the medication, as tolerance usually manifests as a reduced effect of the medication on relieving chest pain. A headache is more likely a sign of the medication's potency, as it indicates that the nitroglycerin is reaching the systemic circulation.

Choice C reason: A headache is an expected adverse effect of the medication, as nitroglycerin causes vasodilation of the cerebral vessels, which can result in increased intracranial pressure and pain. A headache is usually mild and transient, and can be relieved by taking analgesics, such as acetaminophen.

Choice D reason: A headache is not an indication of an allergy to the medication, as an allergic reaction usually causes other symptoms, such as rash, itching, swelling, or difficulty breathing. A headache is more likely a pharmacological effect of the medication, rather than an immunological response.