All of the following are features of metoprolol in comparison to propanolol EXCEPT
Metoprolol is a selective beta-1 blocker, while propranolol is a non-selective beta-blocker. So, metoprolol would have less effect on beta-2 receptors. That means metoprolol is less likely to cause bronchoconstriction, making it safer for patients with asthma. So, if one of the options says metoprolol causes more bronchoconstriction than propranolol, that would be incorrect and the correct answer to the question.
Now, looking at the options. The question says "EXCEPT," so the correct answer is the one that does NOT apply. Let's think about other differences. Metoprolol has intrinsic sympathomimetic activity (ISA)? No, propranolol has some ISA, but metoprolol doesn't. So if an option states that metoprolol has ISA, that's wrong. Also, metoprolol is more cardioselective, so it's used more for heart conditions without affecting the lungs. Propranolol is used for more than just the heart, like migraine prophylaxis.
Another point is lipid solubility. Metoprolol is more lipid-soluble, which affects its metabolism and distribution. Propranolol is more protein-bound. Also, metoprolol has a longer half-life, so it's taken once daily, whereas propranolol might need more frequent dosing. So if an option says metoprolol has a shorter half-life, that's incorrect.
Wait, the question is about the exception. So the correct answer is the statement that is not true for metoprolol compared to propranolol. Let me list possible options. For example, if an option says metoprolol causes more bronchoconstriction than propranolol, that's false because metoprolol is beta-1 selective. Another option might be about ISA, which metoprolol lacks. Or maybe about the effect on the heart rate. Also, metoprolol is less likely to cause cold extremities due to beta-2 blockage. So if an option says metoprolol causes more peripheral vasoconstriction, that's wrong.
So the user's correct answer is the one that states a feature not true for metoprolol compared to propranolol. Let me structure the explanation accordingly, making sure to cover all the necessary points and why each wrong option is incorrect.
**Core Concept**
Beta-blockers like metoprolol (selective Ξ²β antagonist) and propranolol (non-selective Ξ² antagonist) differ in receptor selectivity, side effect profiles, and clinical applications. The question tests understanding of these pharmacodynamic differences.
**Why the Correct Answer is Right**
Metoprolol selectively blocks Ξ²β-adrenergic receptors, minimizing effects on Ξ²β-receptors in the lungs and blood vessels. Propranolol, being non-selective, blocks both Ξ²β and Ξ²β receptors, leading to bronchoconstriction and peripheral vasoconstriction. Thus, metoprol