ClassIndications
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- suppression of hepatic gluconeogenesis
- activates AMP-activated protein kinase
(AMPK)
- Other effects:
- Duration of action is 8-12 hours
- The rare side effect, lactic acidosis, is thought to be caused by
decreased liver uptake of serum lactate, one of the substrates of
gluconeogenesis
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
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