metformin and sitagliptin (Janumet)
Omudhome Ogbru, PharmD
Omudhome Ogbru, PharmD
Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.
Medical and Pharmacy Editor:
GENERIC NAME: metformin and sitagliptin
BRAND NAME: Janumet
DRUG CLASS AND MECHANISM: 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.
GENERIC AVAILABLE: No
PREPARATIONS: Tablets: 50/500 and 50 mg/1000 mg
STORAGE: Tablets should be stored at room temperature, 15-30 C (59-86 F)
PRESCRIBED FOR: Janumet is combined with diet and exercise to improve blood glucose levels in patients with type 2 diabetes. It is not be used for treating type 1 diabetes.
DOSING: Janumet is taken twice daily with meals, and the starting dose is based on the patient's current dose of sitagliptin and metformin. The maximum dose of Janumet is 100/2000 mg daily.
DRUG INTERACTIONS: 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.
PREGNANCY: 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.
NURSING MOTHERS: 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.
SIDE EFFECTS AND PRECAUTIONS: The most common side effects of Janumet are abdominal pain, nausea diarrhea, vomiting, and hypoglycemia. 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.
Reference: FDA Prescribing Information for Janumet
Last Editorial Review: 7/28/2010 12:55:47 PM
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