Metformin & Sitagliptin (Janumet): Diabetes Drug Side Effects & Dosage

What is metformin and sitagliptin? What is Janumet used for?

Janumet is a combination of two drugs, metformin and sitagliptin, that are used for reducing blood glucose (sugar) levels in individuals with type 2 diabetes. The FDA approved Janumet in March 2007.

Insulin is a hormone produced by the pancreas. It limits blood glucose levels by reducing the amount of glucose released by the liver into the blood and by increasing the removal of glucose from blood by muscle and fat tissues. Type 2 diabetes results when there is reduced sensitivity of muscle and fat to the effects of insulin. When the diabetes progresses, the pancreas produces less insulin. Both defects result in increased levels of glucose in the blood.

Metformin is an oral medication that lowers blood glucose by increasing the sensitivity of liver, muscle, fat, and other tissues to the effects of insulin. Increasing the sensitivity of tissues to insulin causes more glucose to be removed from blood and thereby reduces the level of glucose in the blood. In scientific studies, metformin reduced the complications of diabetes such as heart disease, blindness and kidney disease.

Sitagliptin is an oral drug that reduces blood glucose levels in patients with type 2 diabetes. Following a meal, incretin hormones such as glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are released from the intestine, and their levels increase in the blood. GLP-1 and GIP reduce blood glucose by increasing the production and release of insulin from the pancreas. GLP-1 also reduces blood glucose by reducing the secretion by the pancreas of glucagon, a hormone that increases the production of glucose by the liver and raises the level of glucose in the blood. The net effect of increased release of GLP-1 and GIP is to reduce blood glucose levels. In addition, sitagliptin inhibits the enzyme, dipeptidyl peptidase-4 (DPP-4) that destroys GLP-1 and GIP and thereby increases the levels and activity of both hormones and thereby the release of insulin. As a result, blood glucose levels fall.

What brand names are available for metformin and sitagliptin?


Is metformin and sitagliptin available as a generic drug?


Do I need a prescription for metformin and sitagliptin?


What are the side effects of metformin and sitagliptin?


Lactic acidosis is a serious side effect of metformin that occurs in one out of every 30,000 patients and is fatal in 50% of cases. The symptoms of lactic acidosis are weakness, trouble breathing, abnormal heartbeats, unusual muscle pain, stomach discomfort, light-headedness and feeling cold. Patients at risk for lactic acidosis include those with reduced function of the kidneys or liver, congestive heart failure, severe acute illnesses, and dehydration. Janumet should be discontinued immediately if lactic acidosis is suspected.

Common Side Effects

  • There have been postmarketing reports of acute pancreatitis,  including fatal and non-fatal hemorrhagic or necrotizing pancreatitis. If pancreatitis is suspected, promptly discontinue Janumet.
  • Heart failure has been observed with two other members of the DPP-4 inhibitor class. Consider risks and benefits of Janumet in patients who have known risk factors for heart failure. Monitor patients for signs and symptoms.
  • There have been postmarketing reports of acute renal failure,
  • sometimes requiring dialysis. Before initiating JANUMET and at
  • least annually thereafter, assess renal function.
  • Vitamin B12 deficiency: Metformin may lower Vitamin B12 levels. Measure hematologic parameters annually. When used with an insulin secretagogue (e.g., sulfonylurea) or with insulin, a lower dose of the insulin secretagogue or insulin may be required to reduce the risk of hypoglycemia.
  • There have been postmarketing reports of serious allergic and hypersensitivity reactions in patients treated with sitagliptin (one of the components of JANUMET), such as anaphylaxis, angioedema, and exfoliative skin conditions including Stevens-Johnson syndrome. In such cases, promptly stop JANUMET, assess for other potential causes, institute appropriate monitoring and treatment, and initiate alternative treatment for diabetes.
  • Severe and disabling arthralgia has been reported in patients taking DPP-4 inhibitors. Consider as a possible cause for severe joint pain and discontinue drug if appropriate.
  • There have been postmarketing reports of bullous pemphigoid requiring hospitalization in patients taking DPP-4 inhibitors. Tell patients to report development of blisters or erosions. If bullous pemphigoid is suspected, discontinue Janumet.

What is the dosage for metformin and sitagliptin?

Formulation: 50 mg sitagliptin/500 mg metformin HCl and 50 mg sitagliptin/1000 mg metformin HCl

  • Individualize the starting dose of Janumet based on the patient’s current regimen.
  • Adjust the dosing based on effectiveness and tolerability while not exceeding the maximum recommended daily dose of 100 mg sitagliptin and 2000 mg metformin.
  • Give twice daily with meals, with gradual dose escalation, to reduce the gastrointestinal effects due to metformin.
  • Prior to initiation, assess renal function with estimated glomerular filtration rate (eGFR)
  • Do not use in patients with eGFR below 30 mL/min/1.73 m2.
  • Janumet is not recommended in patients with eGFR between 30 and less than 45 mL/min/1.73 m2
  • Janumet may need to be discontinued at time of, or prior to, iodinated contrast imaging procedures.

Which drugs or supplements interact with metformin and sitagliptin?

Cimetidine (Tagamet), by decreasing the elimination of
metformin from the body, can increase the level of metformin in the blood by
40%. This may increase the frequency of side effects from metformin and Janumet.

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Is metformin and sitagliptin safe to take if I’m pregnant or breastfeeding?

There are no adequate studies of Janumet or the individual
components in pregnant women. Most experts agree that insulin is the appropriate
treatment for diabetes during pregnancy.

It is unknown whether sitagliptin is secreted in human
breast milk. However, metformin is excreted into breast milk and can therefore
be transferred to the nursing infant.

What else should I know about metformin and sitagliptin?

What preparations of metformin and sitagliptin are available?

Tablets: 50/500 and 50 mg/1000 mg

How should I keep metformin and sitagliptin stored?

Tablets should be stored at room temperature, 15-30 C (59-86 F)

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