Final answer:
Metformin is the recommended oral hypoglycemic agent for patients with an allergy to sulfa drugs because it is not part of the sulfonylurea class and does not contain sulfa.
Step-by-step explanation:
When considering which oral hypoglycemic agent to give to patients who have an allergy to sulfa drugs, Metformin is a suitable option. Gliclazide, which is a sulfonylurea, stimulates the beta cells of the pancreas to secrete insulin but is not advisable for patients with sulfa allergies due to its sulfonylurea content. Pioglitazone and Sitagliptin are other non-sulfonylureas, but Metformin is the most common first-line treatment for type 2 diabetes and does not have sulfa content, making it a safer choice for those with sulfa drug allergies. Metformin works by reducing glucose production in the liver (gluconeogenesis) and increasing insulin sensitivity, thus helping to lower blood glucose levels without the risk associated with sulfonylureas.