**Question:** Propanolol is contraindicated in a patient of angina pectoris who is already receiving:

A. Calcium channel blockers
B. Nitrates
C. ACE inhibitors
D. Beta-adrenergic receptor agonists

**Core Concept:**

Propanolol is a beta-blocker, which is used to treat various cardiovascular disorders, including angina pectoris. However, in patients already receiving other medications with similar effects, propranolol can lead to excessive bradycardia, hypotension, and worsening of angina symptoms.

**Why the Correct Answer is Right:**

The correct answer is B (nitrates):

Nitrates, specifically nitroglycerin, are commonly used in the management of angina pectoris to dilate coronary arteries and improve blood flow to the heart muscle. When combined with a beta-blocker like propranolol, it increases the risk of hypotension and bradycardia, leading to worsening of angina symptoms.

**Why Each Wrong Option is Incorrect:**

A (calcium channel blockers): These drugs, such as verapamil and diltiazem, work by blocking calcium channels in cardiac and smooth muscle cells. When combined with propranolol, the risk of bradycardia and hypotension is increased, but the effect on angina management is not as significant as with nitrates.

C (ACE inhibitors): Angiotensin-converting enzyme inhibitors, like lisinopril and ramipril, are used for hypertension, heart failure, and post-myocardial infarction care. Combining ACE inhibitors with beta-blockers like propranolol can lead to increased risk of hypotension and bradycardia, but the worsening of angina symptoms is less pronounced than with nitrates.

D (beta-adrenergic receptor agonists): Beta-adrenergic receptor agonists, like isosorbide and dopamine, are used to increase heart rate and contractility in cardiac disorders. Combining beta-agonists with beta-blockers like propranolol can lead to excessive bradycardia and hypotension, worsening the condition in patients with angina pectoris.

**Clinical Pearl:**

When prescribing beta-blockers like propranolol for angina pectoris management, it is essential to avoid combining these medications with nitrates, ACE inhibitors, or beta-adrenergic receptor agonists. This is because the combination of beta-blockers and these drugs can lead to significant bradycardia and hypotension, worsening the patient's angina symptoms. Instead, consider alternative medications like calcium channel blockers or nitrates for angina management, while ensuring a proper assessment of the patient's response to the treatment.