Generic Name

Metformin Hydrochloride

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Classification

FDA Approved Indications

• Type 2 diabetes mellitus (oral monotherapy or adjunct to other agents)

Mechanism of Action

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

Dosage and Administration

Adult: Starting dose usually 500 mg twice daily or 850 mg once daily, titrated based on glycemic response.

Pediatric: Approved for children ≥10 years; starting dose typically 500 mg once daily, titrated gradually.

Geriatric: Careful dose titration due to renal function considerations.

Renal Impairment: Contraindicated in renal impairment (eGFR <30 mL/min/1.73 m²); caution and dose adjustments in eGFR 30-45 mL/min/1.73 m².

Hepatic Impairment: Use with caution; risk of lactic acidosis.

Pharmacokinetics

Absorption: Absorbed from the gastrointestinal tract, with bioavailability of approximately 50-60%.

Distribution: Distributed to body tissues, minimal plasma protein binding.

Metabolism: Not metabolized.

Excretion: Excreted unchanged in urine.

Half Life: Approximately 4 to 8.7 hours.

Contraindications

• Renal impairment (eGFR <30 mL/min/1.73 m²)
• Acute or chronic metabolic acidosis, including diabetic ketoacidosis.
• Hepatic impairment

Precautions

• Use with caution in aging adults, due to increased risk of lactic acidosis.
• Ensure proper hydration.

Adverse Reactions - Common

• Gastrointestinal upset (nausea, vomiting, diarrhea) (Common)
• Unpleasant metallic taste (Less common)

Adverse Reactions - Serious

• Lactic acidosis (Rare, but serious)

Drug-Drug Interactions

• Radiologic contrast agents (risk of acute renal failure and lactic acidosis)
• Other medications affecting renal function or lactic acid levels

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Patient/Family Teaching

• Take medication with meals to minimize GI side effects.
• Report symptoms of lactic acidosis: weakness, fatigue, hyperventilation, abdominal pain.
• Maintain hydration.

Special Considerations

Black Box Warnings:

• Risk of lactic acidosis, especially in renal impairment.

Genetic Factors: None specified.

Lab Test Interference: May interfere with serum lactate and blood glucose tests.

Overdose Management

Signs/Symptoms: Lactic acidosis, hyperventilation, abdominal pain, hypotension, somnolence.

Treatment: Immediate discontinuation of drug, supportive care, and possibly hemodialysis.

Storage and Handling

Storage: Store at room temperature, protected from moisture.

Stability: Stable under recommended conditions.