Which medication reduces uptake of brown fat if taken before a PET exam?

Propranolol is a non-selective beta-adrenergic antagonist that can reduce the activity of brown adipose tissue (BAT). Brown fat is known for its role in thermogenesis, which can significantly influence the uptake of radiotracers during a PET scan. By blocking the beta-adrenergic receptors, propranolol decreases catecholamine stimulation of brown fat, hence reducing its uptake of PET tracers.

In the context of a PET exam, patients are often advised to avoid substances that may induce increased brown fat activity, as this could lead to significant background noise and misinterpretation of the PET scan results. The use of propranolol prior to imaging can help normalize the metabolic rate of brown fat, ensuring clearer and more accurate imaging by enhancing the contrast between normal and pathological tissues.

The other medications listed—metoprolol, atenolol, and carvedilol—are selective or non-selective beta-blockers but may not have the same robust effect on brown fat uptake as propranolol. Each of these medications may play a role in managing heart rate and blood pressure but may not significantly influence brown fat activity in the same way, which is why propranolol is specifically preferred for this purpose in the context