Which of the following drugs should be categorized under "Do Not Use" for antihistamines?

The categorization of "Do Not Use" for antihistamines primarily applies to individuals with a known allergy to the drug. When a patient has a documented allergy, exposure to the antihistamine can trigger serious allergic reactions, such as anaphylaxis, which can be life-threatening. This is a clear indication that the drug should be avoided entirely.

In the case of the other options, while certain precautions should be taken for patients with conditions like pregnancy, cardiac disease, or glaucoma, these conditions do not universally preclude the use of antihistamines. For example, certain antihistamines may still be deemed safe for use during pregnancy or may be prescribed with caution in patients with cardiac issues or glaucoma, based on the specific drugs chosen and the patient's overall health status. Therefore, known allergy stands out as an absolute contraindication for the use of any specific antihistamine.