Why should nonselective beta-blockers be used with caution in patients with asthma or COPD?

• A. They can cause bronchoconstriction by blocking beta-2 receptors; prefer cardioselective beta-blockers and monitor respiratory status.
• B. They cause tachycardia.
• C. They have no respiratory effects.
• D. They are contraindicated in all respiratory diseases.

Answer: (A)