DrugFriday: Metformin


Metformin is an oral hypoglycemic agent or anti diabetes drug belonging to the class Biguanides.

Mechanism Of Action:

Metformin acts as an insulin sensitizing agent, thus reducing insulin resistance. It also decreases glucose production by liver and intestinal glucose absorption.


Metformin is metabolized mainly through kidneys and is excreted through urine. It is dialysable.


Type 2 Diabetes: Metformin counters insulin resistance, the chief pathology of Type 2 Diabetes,thus reducing insulin levels.
PCOS: A large percentage of PCOS patients have insulin resistance or type 2 Diabetes for which Metformin is indicated. It also reduces signs of Insulin resistance.
Obesity: Metformin is anorexigenic and promotes weight loss.


In type 2 Diabetes, maximum 2500 mg a day, in divided doses is given as monotherapy or in combination
In PCOS, 850-1000 mg a day is given generally as monotherapy
In kidney impairment, dose is adjusted as per creatinine clearance.


  • Caution is advised in congestive heart failure, fever, trauma, surgery, the elderly or hepatic impairment
  • Instruct patients to avoid heavy alcohol use
  • Suspend therapy prior to any type of surgery
  • Rare, but serious, lactic acidosis can occur due to accumulation
  • May cause ovulation in anovulatory and premenopausal PCOS patients
  • May be necessary to discontinue therapy with metformin and administer insulin if patient is exposed to stress (fever, trauma, infection)

Adverse Effects:

  • Hypoglycemia
  • Diarrhea
  • Flatulence
  • Weakness
  • Myalgia
  • Lactic acidosis (rare)
  • Low serum vitamin B-12
  • Nausea/vomiting


The major interactions are with contract agents and with ethanol.
Minor interactions are with amiodarone, antibiotics like quinilones, antiviral drugs etc.

Use In Pregnancy:

Metformin is a category B drug in pregnancy, meaning studies in humans have not shown major teratogenicity.

Common Brand Names In India:

Glycomet, Glyciphage, Carbophage, Cetapin


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