Which of the following beta blockers does NOT have intrinsic sympathomimetic activity?

Timolol is a non-selective beta-adrenergic antagonist that does not possess intrinsic sympathomimetic activity (ISA). This means that while it blocks the effects of catecholamines at the beta-receptors, it does not stimulate these receptors to any significant degree. This property makes timolol particularly effective in lowering intraocular pressure and is why it is widely used in the management of glaucoma.

In contrast, other beta blockers such as carteolol have ISA, allowing them to exert a mild stimulating effect on beta receptors, which can influence their pharmacologic profiles and potential side effects. Understanding the presence or absence of ISA in beta blockers is crucial for tailoring treatment regimens for conditions like glaucoma, hypertension, and other cardiovascular issues. This is why recognizing timolol's lack of ISA is important in clinical practice.