Class: Biguanide, Hypoglycemic
Dosage Forms. Tablet: 500 mg, 850 mg, 1000 mg; Tablet, Extended Release: 500 mg, 750 mg, 1000 mg; Solution: 500 mg/5 mL
Common FDA Label Indication, Dosing and Titration.
1. Diabetes mellitus, Type II: Adults, 500-1000 mg immediate release po bid, may titrate to max dose 2250 mg/d or 500-2000 mg extended release po daily, may titrate to max dose 2000 mg/d; Children 10 y and older, 500-1000 mg immediate release po bid, may titrate to max dose 2000 mg/d
1. Polycystic ovary disease: 500 mg po tid
MOA. Metformin is a biguanide antihyperglycemic agent. It does not affect insulin secretion; rather, it reduces hepatic glucose production and enhances glucose utilization by muscle.
Drug Characteristics: Metformin
Medication Safety Issues: Metformin
Drug Interactions: Metformin
Adverse Reactions: Metformin
Efficacy Monitoring Parameters. Preprandial blood glucose between 70 and 130 mg/dL, HbA 1c<7%.
Toxicity. Renal function, complete blood count, B12 levels. Seek medical attention if severe skin rash, muscle weakness or pain, yellowing of eyes or skin, unusual bruising, or bleeding.
Key Patient Counseling Points. Monitor blood glucose in frequent intervals (2-4 times per day); if <70 mg/dL, eat candy or sugar and contact prescriber. Take with morning meal if daily dosing. Take with morning and evening meal if bid. Drink plenty of liquids to improve elimination of metformin. Avoid alcohol; this increases the risk of lactic acidosis.
Clinical Pearls. Patient having procedure with iodinated contrast: withhold metformin prior to or at the time of the procedure and for 48 h following the procedure. Restart metformin only after kidney function has been reevaluated and found to be normal. Take extended-release product with food or milk. Immediate release may be taken with food, if GI upset occurs. Metformin is first-line therapy for Type II diabetes. Metformin does not cause hypoglycemia when used as a single agent.