A 52-year-old man with newly diagnosed type 2 diabetes mellitus presents with HbA1c of 8.2%. He has no contraindications to any antidiabetic agent. According to current guidelines, what is the first-line drug of choice for monotherapy in this patient?

Explanation

## First-Line Agent in Type 2 Diabetes **Key Point:** Metformin is the universally recommended first-line monotherapy for type 2 diabetes mellitus in the absence of contraindications [cite:KD Tripathi 8e Ch 54]. ### Why Metformin? 1. **Mechanism of action**: Decreases hepatic glucose production and improves peripheral insulin sensitivity without stimulating insulin secretion. 2. **Cardiovascular benefit**: Reduces cardiovascular mortality and all-cause mortality in overweight/obese patients. 3. **Weight neutral**: Does not cause weight gain (unlike sulfonylureas and thiazolidinediones). 4. **No hypoglycemia risk**: Does not cause hypoglycemia when used as monotherapy. 5. **Cost-effective**: Inexpensive and widely available. ### Contraindications to Metformin | Contraindication | Reason | |---|---| | eGFR < 30 mL/min/1.73m² | Risk of lactic acidosis | | Acute illness, sepsis | Increased lactate production | | Liver disease | Impaired metabolism | | Acute MI, cardiac failure | Tissue hypoxia | | Contrast dye administration | Acute renal injury risk | **High-Yield:** Metformin is the only oral hypoglycemic agent recommended as first-line monotherapy by ADA, EASD, and Indian guidelines (RSSDI). **Clinical Pearl:** Even in patients with mild renal impairment (eGFR 30–45), metformin can be used with dose adjustment and monitoring. The absolute contraindication is eGFR < 30.