Metformin

Class

Indications

Administration/Absorption

    • Oral

    • Absorbed over 6 hours

    • Bioavailability is 50 to 60% under fasting conditions.

    • Administration with food decreases and delays absorption

    • Peak action occurs 3 hours after oral administration.

Dosage

Distribution

    • VOD is 654 L for metformin 850 mg administered as a single dose

    • Negligibly bound to plasma proteins

Mechanism

Excretion

    • Half-life 6.2 hours

    • Metformin is not metabolized and is excreted unchanged in the urine

    • Approximately 90% of the drug is eliminated in 24 hours in those with healthy renal function

    • Renal clearance of metformin is approximately 3.5 times that of creatinine clearance

      • Indicates that tubular secretion is the primary mode of metformin elimination.

Side effects

    • Its main side effects are dyspepsia, nausea and diarrhea

      • Dose titration and/or use of smaller divided doses may decrease side effects

Interactions

Contraindications

    • Risk of lactic acidosis means metformin should be avoided in:

      • severely compromised renal function (creatinine clearance < 30 ml/min)

      • acute/decompensated heart failure

      • severe liver disease

      • for 48 hours after the use of iodinated contrast dyes