Question
Metformin.
Answer
Metformin is a biguanide, first-line oral therapy for type 2 diabetes.
MOA: activates AMP-activated protein kinase (AMPK) in hepatocytes, suppressing hepatic gluconeogenesis (dominant mechanism) and modestly increasing peripheral insulin sensitivity/glucose uptake. Does not stimulate insulin release, so carries essentially no hypoglycemia risk as monotherapy.
Uses: type 2 diabetes mellitus (first-line), polycystic ovary syndrome (improves insulin sensitivity).
Adverse effects: GI upset (nausea, diarrhea), lactic acidosis (rare but serious, risk amplified by renal impairment — contraindicated/dose-adjusted in significant renal impairment and temporarily withheld around iodinated contrast administration), vitamin B12 deficiency with long-term use.