metformin hydrochloride

CLINICAL USE

Non-insulin dependent diabetes mellitus Polycystic ovary syndrome

DOSE IN NORMAL RENAL FUNCTION

500 mg 3 times a day; maximum 2 g daily in divided dosesPolycystic ovary syndrome: 1.5–1.7 g daily in 2–3 divided doses

PHARMACOKINETICS

Molecular weight :165.6

%Protein binding :Negligible

%Excreted unchanged in urine : 100

Volume of distribution (L/kg) :1–4

half-life – normal/ESRD (hrs) :2–6/prolonged

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

40–50 25–50% of dose10–40 25% of dose. See ‘Other Information’

<10 : Avoid. See ‘Other Information’

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD :Unknown dialysability. Avoid

HD :Dialysed. Avoid

HDF/high flux :Dialysed. Avoid

CAV/VVHD :Probably dialysed. Avoid

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugs

Alcohol: increased risk of lactic acidosis Cimetidine: Inhibits renal excretion of metformin

ADMINISTRATION

Reconstition

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Route

Oral

Rate of Administration

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Comments

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OTHER INFORMATION

Lactic acidosis is a rare but serious metabolic complication that can occur due to metformin accumulation. Reported cases have occurred primarily in diabetic patients with significant renal impairmentAs metformin is renally excreted eGFR values should be determined before initiating treatment and regularly thereafter:at least annually in patients with —normal renal functionat least 2–4 times a year in patients —with an eGFR at the lower limit of normal and in elderly subjectsSpecial caution should be exercised in the elderly in situations where renal function may become impaired, e.g. initiating therapy with antihypertensives, diuretics

See how to identify renal failure stages according to GFR calculation

See how to diagnose irreversible renal disease

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