Janumet XR (sitagliptin and metformin hydrochloride extended-release)
Janumet XR
Metformin Hydrochloride, Sitagliptin Phosphate
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WHAT IS JANUMET XR?

Janumet XR is an oral medication that includes a combination of two antidiabetic medications, metformin and sitagliptin. It is indicated in adults with type 2 diabetes mellitus (T2DM) to improve glycemic control in addition to diet and exercise. Controlling hyperglycemia prevents downstream complications such as kidney damage, loss of limbs, blindness, heart attack, stroke, or nerve problems. It is important that diabetes remains controlled to lessen the chance of related complications. Janumet XR is not indicated for the treatment of  type I diabetes.

HOW DOES JANUMET XR WORK?

Metformin, a biguanide, and sitagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, work together through a complementary mechanism to improve glycemic control. The individual components of Janumet XR work in the following ways:

Sitagliptin

Incretin hormones are important in glycemic control and include glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). After meals, the intestine releases these incretin hormones in response to increased blood glucose concentrations. These hormones stimulate insulin release from pancreatic beta cells, thus regulating the blood glucose levels. However, GLP-1 and GIP can be inactivated by an enzyme called DPP-4. Sitagliptin inhibits DPP-4, thus increasing incretin hormone levels and insulin release to mediate blood sugar levels.

Metformin

Metformin is a biguanide that lowers the production of hepatic glucose, lowers absorption of glucose in the intestine, and improves insulin sensitivity through increasing peripheral glucose. Insulin release does not change with metformin, however, fasting levels of insulin and day-long plasma insulin response can be lowered.

SIDE EFFECTS

Common side effects include:

  • Nausea, vomiting, or stomach upset
  • Diarrhea or constipation
  • Headache
  • Joint or muscle pain
  • Back pain
  • Weakness
  • A metallic taste in the mouth
  • Cold symptoms such as runny or stuffy nose, sneezing, and sore throat

WARNINGS AND PRECAUTIONS

Lactic acidosis

There have been multiple reports of lactic acidosis with metformin use, with some being fatal cases. Onset was typically gradual with symptoms including muscle pain, abdominal pain, drowsiness, and respiratory distress. More severe cases of acidosis included symptoms such as hypothermia, hypotension, and bradyarrhythmias. The signs and symptoms were accompanied by increased blood lactate concentrations, anion gap acidosis, and an elevated lactate/pyruvate ratio. There are multiple risk factors that increase an individual’s chance of developing lactic acidosis while on metformin. Risk factors and subsequent risk reduction measures include:

  • Renal impairment – Do not use in patients with an eGFR of less than 45 mL/min/1.73 m2
  • Age 65 or greater – Assess renal function more often
  • Radiological studies with contrast – Discontinue Janumet XR prior to an iodinated contrast imaging procedure in patients with an eGFR between 30 and 60 mL/min/1.73 m2 and in patients with liver disease, alcoholism, or heart failure
  • Surgery – Hold Janumet XR while patients have restricted food and fluid intake
  • Hypoxic states – Stop Janumet XR when hypoxic states occur, such as in acute congestive heart failure, cardiovascular collapse, acute myocardial infarction, and sepsis
  • Alcohol – Avoid excessive alcohol intake
  • Hepatic impairment – Do not use Janumet XR if patient exhibits signs of hepatic disease

Pancreatitis

Both fatal and non-fatal hemorrhagic or necrotizing acute pancreatitis cases have been reported. If a patient experiences any signs or symptoms of pancreatitis, Janumet XR should be stopped immediately and the pancreatitis should be managed appropriately.

Heart Failure

Other DPP-4 inhibitors have demonstrated an association with heart failure. Take caution when using Janumet XR in patients with a history of heart failure or renal impairment, and monitor therapy closely. If heart failure occurs while taking Janumet XR, consider stopping therapy.

Acute Renal Failure

There have been cases of worsening renal function, such as acute renal failure and the need for dialysis. Renal function should be evaluated before initiation of Janumet XR and throughout therapy. If a patient’s eGFR is less than 45 mL/min/1.73 m2, treatment with Janumet XR is not recommended. If renal dysfunction is expected to develop, like in the elderly, renal function should be evaluated more often. Stop Janumet XR in the case of renal impairment.

Vitamin B12 Deficiency

Studies have shown a decrease in vitamin B12 levels with the use of metformin. Monitor hematologic measures annually and vitamin B12 parameters every 2 to 3 years for patients taking Janumet XR. If abnormalities are present, manage appropriately with Janumet XR discontinuation or vitamin B12 supplementation.

Hypoglycemia with Concomitant Use of Insulin Products

Janumet XR can cause hypoglycemia when used in combination with other products that lower blood glucose, such as insulin. Dose adjustments to insulin may be required to prevent development of hypoglycemia.

Hypersensitivity Reactions

Sitagliptin has been shown to cause severe hypersensitivity reactions, including anaphylaxis, angioedema, and Stevens-Johnson syndrome within 3 months of starting Janumet XR. If these events occur, Janumet XR should be discontinued and alternative therapies should be explored.

Severe and Disabling Arthralgia

DPP-4 inhibitors have demonstrated severe and disabling arthralgias that subside upon drug withdrawal. If experiencing pain in one’s joints, patients should stop taking Janumet XR and avoid other DPP-4 inhibitors.

Bullous Pemphigoid

Monitor patients for the formation of erosions or blisters, as there have been reported cases of bullous pemphigoid with DPP-4 inhibitors. Treatment of this phenomenon usually requires hospitalization and immunosuppressive therapy. If suspected, discontinue Janumet XR and obtain a dermatologist referral.

DRUG INTERACTIONS

Carbonic Anhydrase Inhibitors (CAI)

Carbonic anhydrase inhibitors can lower serum bicarbonate and cause non-anion gap metabolic acidosis. When used concomitantly with Janumet XR, this combination can elevate an individual’s risk for developing lactic acidosis. Patients that are taking these drugs in collaboration should be frequently monitored. Examples of CAIs include topiramate and acetazolamide.

Drugs that Decrease Clearance of Metformin

Medications that interfere with the renal elimination of metformin should be avoided. Drugs like ranolazine, dolutegravir, and cimetidine can increase a patient’s systemic exposure to metformin and elevate the risk of lactic acidosis.

Alcohol

Patients should avoid excessive alcohol intake. Alcohol has been shown to increase metformin’s effect on lactate metabolism, causing increased risk for lactic acidosis.

Other Drugs Affecting Glycemic Control

When used in combination with other drugs that can cause hypoglycemia, the risk for developing hypoglycemia with Janumet XR is increased. Patients should be monitored for signs of hypoglycemia when on concomitant glucose-altering agents such as steroids, diuretics, and phenytoin.

FREQUENTLY ASKED QUESTIONS

If you miss a dose of Janumet XR, take the dose as soon as you remember. If it is time for the next dose at the time that you remember, skip the missed dose and return to your normal dosing schedule. Do not take more than one dose of Janumet XR at the same time.

Janumet XR can be taken long term to control type II diabetes mellitus.

Janumet XR should be taken once daily with meals.

If you overdose with Janumet XR, you should immediately go to the emergency room or contact the Poison Control Center. Overdosing on Janumet XR increases an individual’s chance of developing hypoglycemia or lactic acidosis.

Avoid excessive alcohol intake, as this increases one’s risk of developing lactic acidosis while on Janumet XR.

Common side effects of Janumet XR include:

  • Cold symptoms such as a sore throat or stuffy or runny nose
  • Upset stomach, bloating, and indigestion
  • Headache
  • Nausea, vomiting, and diarrhea
  • Weakness
  • Upper respiratory infection
  • Low blood sugar
  • Joint or muscle pain
  • Metallic taste in the mouth

It is important that you tell your doctor all of the medications, vitamins, and supplements that you take. Additionally, tell your doctor if you:

  • Have inflammation of your pancreas (pancreatitis)
  • Have kidney problems
  • Have liver problems
  • Have heart failure
  • Drink alcohol frequently or drink large amounts of alcohol at once (“binge” drinking)
  • Will be receiving injection of dye or contrast agents for an x-ray procedure
  • Have low vitamin B12 levels in your blood
  • Are pregnant or plan to become pregnant
  • Are breastfeeding or plan to breastfeed
  • Are a premenopausal woman