Correct Answer » C Explanation

Metformin

• An oral antihyperglycemic drug (biguanide)

Reason for withholding on day of surgery:

Risk of:

• Lactic acidosis, especially in:
  • Renal hypoperfusion
  • Hypoxia
  • Contrast use
  • Hemodynamic instability

During surgery, patients may develop:

• Hypotension
• Renal impairment
• Tissue hypoxia

Hence:

Metformin is usually stopped on the day of surgery (sometimes 24–48 hours before major surgery).

Explanation of Other Options

A. Atenolol 

• Beta-blockers are generally continued
• Sudden withdrawal may cause:
  • Rebound hypertension
  • Tachycardia
  • Myocardial ischemia

B. Amlodipine 

• Calcium channel blockers are usually continued
• Help maintain blood pressure control

D. Statin 

• Statins are generally continued perioperatively
• May reduce cardiovascular complications