Which of the following drugs is known to decrease absorption when taken with food?

Levothyroxine is known to decrease absorption when taken with food, particularly with meals that are high in fiber or contain calcium and iron. This is significant because levothyroxine, which is a synthetic form of the thyroid hormone thyroxine, requires fasting for optimal absorption. Ideally, it should be taken on an empty stomach, usually in the morning, to ensure that the maximum amount of the medication is absorbed into the bloodstream. When food is introduced, especially certain types of food, it can bind to the medication and impede its absorption, leading to insufficient levels of thyroid hormone and potentially ineffective treatment of hypothyroidism.

In contrast, the other medications listed generally do not have the same level of concern regarding food interactions affecting their absorption. Amlodipine is a calcium channel blocker that can be taken with or without food, as food does not significantly impact its absorption. Cetirizine, an antihistamine, also does not critically depend on fasting for absorption, although taking it with food may help reduce the risk of gastrointestinal disturbances. Metoprolol, a beta-blocker, shows variable absorption but isn't significantly affected by the presence of food. It can be taken with or without meals depending on the formulation used.