What medication is most likely prescribed for a patient with oral candidiasis?

Nystatin is an antifungal medication specifically effective against fungal infections, including oral candidiasis, also known as thrush. Candidiasis is caused by an overgrowth of Candida yeast, and Nystatin works by binding to the fungal cell membrane, altering its permeability, which ultimately leads to cell death. This targeted action makes Nystatin a first-line treatment for such infections in the oral cavity.

Other medications listed are not appropriate for treating oral candidiasis. Acyclovir is an antiviral agent primarily used for herpes virus infections. Isoniazid is an antibiotic used for tuberculosis and does not have antifungal properties. Amoxicillin is a broad-spectrum antibiotic effective against various bacterial infections but is not effective against fungal infections like candidiasis. Therefore, Nystatin is the most suitable choice for treating oral candidiasis.