Which antidiabetic agent is commonly first-line, and what safety concern must be monitored?

• A. Acarbose; risk of hypoglycemia
• B. Metformin; risk of lactic acidosis in CKD or hypoxic states; monitor eGFR and adjust or avoid if eGFR <30
• C. Pioglitazone; risk of fluid retention
• D. Insulin; risk of hypoglycemia

Answer: (B)

Metformin is commonly chosen as the first-line antidiabetic agent because it effectively lowers hepatic glucose production and improves insulin sensitivity without causing hypoglycemia when used alone. It also tends to have weight-neutral effects or modest weight loss, has cardiovascular benefits, and is inexpensive, making it a practical initial option for many adults with type 2 diabetes.

The safety concern to monitor is lactic acidosis, a rare but serious complication more likely in people with reduced kidney function or in hypoxic states. Metformin is cleared by the kidneys, so impaired renal function can lead to drug accumulation and increased lactate production. Therefore, kidney function should be checked with eGFR before starting and monitored during treatment. The drug should be avoided if eGFR is less than 30 mL/min/1.73 m^2; if eGFR is 30–44, dose adjustments and closer monitoring are typically recommended.