**Question:** The dose of Digoxin should be reduced when given along with:

**Core Concept:** Digoxin is a cardiac glycoside used for the treatment of certain cardiac arrhythmias and heart failure. It works by increasing the contractility of the heart muscle and reducing the heart rate. However, its pharmacokinetics can be altered when given in combination with certain drugs.

**Why the Correct Answer is Right:** When digoxin is co-administered with other medications that can increase its bioavailability, such as amiodarone, quinidine, or verapamil, its dose should be reduced. This is because these drugs can enhance the absorption of digoxin, leading to increased plasma concentrations and potential toxicity.

**Why Each Wrong Option is Incorrect:**

A. Beta-blockers: Although beta-blockers can decrease cardiac contractility, they do not significantly affect digoxin levels. Therefore, digoxin dose adjustments are not generally necessary when given together with beta-blockers.

B. Calcium channel blockers: Calcium channel blockers like diltiazem and verapamil can increase digoxin levels by decreasing its elimination. However, the correct answer is to reduce the digoxin dose when combined with verapamil, not dihydropyridine calcium channel blockers.

C. Diuretics: Diuretics, such as furosemide, do not significantly affect digoxin levels or its elimination. Therefore, digoxin dose adjustments are not necessary when given together with diuretics.

D. ACE inhibitors: Angiotensin-converting enzyme (ACE) inhibitors like lisinopril do not affect digoxin levels significantly. Hence, dose adjustments of digoxin are not typically required when given with ACE inhibitors.

**Core Concept:** In summary, co-administration of digoxin with verapamil, a calcium channel blocker, can lead to increased digoxin levels due to decreased elimination. Consequently, the dose of digoxin should be reduced to prevent toxicity. Other options (beta-blockers, diuretics, and ACE inhibitors) do not significantly impact digoxin levels or elimination, so digoxin doses do not need to be adjusted when combined with these medications.

**Why Each Wrong Option is Incorrect:**

A. Beta-blockers: Beta-blockers primarily target beta-receptors and do not significantly influence digoxin levels or elimination. As a result, digoxin doses do not require adjustment when taken with beta-blockers.

B. Diuretics: Diuretics primarily focus on water and electrolyte balance regulation and do not substantially affect digoxin levels or elimination. Consequently, digoxin dosing changes are not necessary when combined with diuretics.

C. ACE inhibitors: Angiotensin-converting enzyme inhibitors (ACE inhibitors) target the renin-angiotensin-aldosterone system and do not significantly influence digoxin levels or elimination. Hence, digoxin doses do not require modification when co-administered with ACE inhibitors.

**Correct Answer and Explanation