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Metformin

Glucophage | Fortamet | Glumetza | Riomet

FDA ApprovedEndocrine AgentsAntidiabetics
FDA: 1994Half-life: 4-8.7 hoursPregnancy: Category B

Overview

Metformin is a biguanide antidiabetic agent used as first-line therapy for type 2 diabetes mellitus. It works primarily by decreasing hepatic glucose production and improving insulin sensitivity.

Indications

  • Type 2 Diabetes Mellitus
  • Polycystic Ovary Syndrome (off-label)
  • Prediabetes (off-label)

Contraindications

  • Severe renal impairment (eGFR < 30)
  • Metabolic acidosis
  • Diabetic ketoacidosis

Mechanism of Action

Decreases hepatic glucose production, decreases intestinal absorption of glucose, and improves insulin sensitivity by increasing peripheral glucose uptake and utilization.

Pharmacodynamics

Metformin lowers both basal and postprandial plasma glucose levels. It does not cause hypoglycemia when used alone because it does not stimulate insulin secretion.

Pharmacokinetics

Absorption
Slowly and incompletely absorbed from the GI tract. Bioavailability is 50-60%.
Distribution
Negligible protein binding. Distributes to red blood cells.
Metabolism
Not metabolized. Excreted unchanged.
Excretion
Eliminated primarily by renal tubular secretion.
Half-life
4-8.7 hours
Bioavailability
50-60%
Protein Binding
Negligible

Dosage

Typical dosage: 500-2000 mg daily in divided doses

Available Forms

  • Tablet
  • Extended-release tablet
  • Oral solution

Side Effects

Common

  • Diarrhea
  • Nausea
  • Abdominal discomfort
  • Metallic taste

Serious

  • Lactic acidosis (rare)
  • Vitamin B12 deficiency

Rare

  • Hypoglycemia (when combined with other agents)

Drug Interactions

Iodinated Contrast Mediamajor

Risk of contrast-induced nephropathy and lactic acidosis. Hold metformin before and after contrast procedures.

Alcoholmoderate

Increased risk of lactic acidosis and hypoglycemia.

Warnings

⚠️BLACK BOX WARNING

Lactic acidosis is a rare but serious metabolic complication. Risk increases with renal impairment, sepsis, dehydration, and excessive alcohol intake.

Pregnancy

Category B

Toxicity

Lactic acidosis in overdose. Hemodialysis is effective for removal.

Overdose

Symptoms include hypoglycemia, lactic acidosis, nausea, vomiting. Supportive care and hemodialysis for severe cases.

References

Looking for patient-friendly information? Visit RemedyDoor for easy-to-read guides about this medication.