Beta blocker with intrinsic sympathomimetic activity is
**Core Concept**
Beta blockers with intrinsic sympathomimetic activity (ISA) are a class of medications that possess both beta-blocking and sympathomimetic properties. These agents are partial agonists at the beta-adrenergic receptor, which means they can stimulate the receptor while also blocking it. This unique property allows them to produce a partial agonist effect at therapeutic doses.
**Why the Correct Answer is Right**
The correct answer is a beta blocker with ISA, which is a characteristic that distinguishes it from other beta blockers. The partial agonist effect of these agents is due to their ability to activate the beta-adrenergic receptor, leading to a decrease in sympathetic tone. This is in contrast to non-selective beta blockers, which only block the receptor without any agonist effect. The ISA property of these agents is mediated by their ability to stabilize the beta-adrenergic receptor in a low-affinity state, which reduces the receptor's responsiveness to endogenous catecholamines.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not possess the ISA property. Non-selective beta blockers, such as propranolol, do not have intrinsic sympathomimetic activity.
**Option B:** This option is incorrect because it is a beta agonist, not a beta blocker. Beta agonists, such as albuterol, stimulate the beta-adrenergic receptor, whereas beta blockers inhibit it.
**Option C:** This option is incorrect because it is a selective beta-1 blocker, which does not have intrinsic sympathomimetic activity. Selective beta-1 blockers, such as metoprolol, are used to treat hypertension and angina, but they do not possess the ISA property.
**Clinical Pearl / High-Yield Fact**
Beta blockers with ISA are often used in patients with asthma or chronic obstructive pulmonary disease (COPD) because they can help to mitigate the bronchoconstrictive effects of beta blockade. This is due to their partial agonist effect, which can help to stabilize the beta-adrenergic receptor and reduce bronchospasm.
**Correct Answer: C. Pindolol. Pindolol is a beta blocker with intrinsic sympathomimetic activity.**