Final answer:
Ketoconazole is not an antihistamine; it is an antifungal medication, unlike Astemizole, Fexofenadine, and Loratadine, which are antihistamines that help with allergy symptoms.
Step-by-step explanation:
The drug that is NOT an antihistamine from the list provided is c. Ketoconazole. Antihistamines, such as Astemizole, Fexofenadine, and Loratadine, work by preventing histamines from stimulating the itching and swelling of body tissues. Conversely, Ketoconazole is an antifungal medication which targets components of fungal cells, like ergosterol, and does not have antihistamine activity. Common antihistamines are used to alleviate allergy symptoms and may be included in treatments for type I hypersensitivity reactions.