Pharmaste Daily: October 19, 2026

Names and formulations

• Metformin hydrochloride: immediate-release oral tablet
• Glumetza: extended-release oral tablet

Immediate-release and extended-release tablets differ in dosing and administration; ER tablets should be swallowed whole and may leave a soft shell in stool.

Common use

Improves glycemic control in type 2 diabetes alongside diet and exercise.

Mechanism of action

Reduces hepatic glucose production, decreases intestinal glucose absorption, and improves insulin sensitivity.

Important adverse effects and monitoring

• Boxed warning: metformin-associated lactic acidosis is rare but serious; risk rises with severe kidney impairment, hypoxic states, liver impairment, and excessive alcohol use.
• Assess eGFR before initiation and periodically; initiation is not recommended at eGFR 30–45 mL/min/1.73 m² and use is contraindicated below 30.
• Monitor vitamin B12 periodically, especially with anemia, neuropathy, or long-term therapy.

Patient counseling

• Take with meals to reduce gastrointestinal effects; swallow ER tablets whole.
• Avoid excessive alcohol and tell the radiology team about metformin before iodinated-contrast procedures.

Interaction to recognize

With: carbonic anhydrase inhibitors such as topiramate

Why it matters: Can increase acidosis risk.

Practical response: Consider more frequent monitoring and reassess symptoms or kidney function when combined.

Check the original sources

• DailyMed — metformin immediate-release prescribing information

  Sections: Boxed Warning; 1 Indications and Usage; 2 Dosage and Administration; 5 Warnings and Precautions; 7 Drug Interactions; 12.1 Mechanism of Action; 17 Patient Counseling Information. Source checked 2026-09-13.

• DailyMed — Glumetza (metformin ER) prescribing information

  Sections: 2 Dosage and Administration; 5.2 Vitamin B12 Deficiency; 17 Patient Counseling Information. Source checked 2026-09-13.

Selected learning points; verify current labeling for the complete prescribing information.