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Lactic acidosis is a rare but serious complication that can occur because of metformin accumulation. The risk increases with conditions such as sepsis, dehydration, excess alcohol intake, hepatic insufficiency, renal impairment, and acute congestive heart failure.
The onset is often subtle, accompanied only by nonspecific symptoms such as malaise, myalgias, respiratory distress, increasing somnolence, and nonspecific abdominal distress.
Laboratory abnormalities include low pH, increased anion gap, and elevated blood lactate.
If acidosis is suspected, JANUMET should be discontinued and the patient hospitalized immediately [see Warnings and Precautions].
When lactic acidosis occurs, it is fatal in approximately 50% of cases. The reported incidence of lactic acidosis in patients receiving metformin is very low (approximately 0.03 cases/1000 patient-years, with approximately 0.015 fatal cases/1000 patient-years). Reported cases have occurred primarily in diabetic patients with significant renal insufficiency, including both intrinsic renal disease and renal hypoperfusion, often in the setting of multiple concomitant medical/surgical problems and multiple concomitant medications.
JANUMET should not be used in patients with type 1 diabetes or for the treatment of diabetic ketoacidosis.
JANUMET has not been studied in combination with insulin.
JANUMET is contraindicated in patients with renal disease or renal dysfunction (serum creatinine levels ≥1.5 mg/dL in males and ≥1.4 mg/dL in females) or abnormal creatinine clearance; acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma; or history of a serious hypersensitivity reaction to JANUMET or sitagliptin (one of the components of JANUMET), such as anaphylaxis or angioedema.
Temporarily discontinue JANUMET in patients undergoing radiologic studies involving intravascular administration of iodinated contrast materials.
Metformin treatment should not be initiated in patients ≥80 years of age unless measurement of creatinine clearance demonstrates that renal function is not reduced, as these patients are more susceptible to developing lactic acidosis. Care should be taken in dose selection and should be based on careful, regular monitoring of renal function.
Because impaired hepatic function has been associated with some cases of lactic acidosis, JANUMET should generally be avoided in patients with clinical or laboratory evidence of hepatic disease.
Before initiation of therapy with JANUMET and at least annually thereafter, renal function should be assessed and verified as normal. In patients in whom development of renal dysfunction is anticipated, particularly in elderly patients, renal function should be assessed more frequently and JANUMET discontinued if evidence of renal impairment is present.
Concomitant medication(s) that may affect renal function or result in significant hemodynamic change or may interfere with the disposition of metformin, such as cationic drugs that are eliminated by renal tubular secretion, should be used with caution.
Cardiovascular collapse (shock) from whatever cause, acute congestive heart failure, acute myocardial infarction, and other conditions characterized by hypoxemia have been associated with lactic acidosis and may also cause prerenal azotemia. When such events occur in patients on JANUMET therapy, the drug should be promptly discontinued.
There have been postmarketing reports of serious 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. Because these reactions are reported voluntarily from a population of uncertain size, it is generally not possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Onset of these reactions occurred within the first 3 months after initiation of treatment with sitagliptin, with some reports occurring after the first dose. If a hypersensitivity reaction is suspected, discontinue JANUMET, assess for other potential causes for the event, and institute alternative treatment for diabetes.
Use of JANUMET should be temporarily suspended for any surgical procedure (except minor procedures not associated with restricted intake of food and fluids) and should not be restarted until the patient’s oral intake has resumed and renal function has been evaluated as normal.
Measurement of hematologic parameters on an annual basis is advised in patients on JANUMET and any apparent abnormalities should be appropriately investigated and managed. Certain individuals (those with inadequate vitamin B12 or calcium intake or absorption) appear to be predisposed to developing subnormal vitamin B12 levels.
In any intravascular contrast studies with iodinated materials, use of JANUMET should be temporarily discontinued at the time of or before the procedure, withheld for 48 hours subsequent to the procedure, and reinstituted only after renal function has been reevaluated and found to be normal.
There have been no clinical studies establishing conclusive evidence of macrovascular risk reduction with JANUMET or with any other oral antidiabetic drug.
Patients should be warned against excessive alcohol intake, either acute or chronic, while taking metformin.
Certain drugs tend to produce hyperglycemia and may lead to loss of glycemic control. When such drugs are administered to a patient receiving JANUMET, the patient should be closely observed to maintain adequate glycemic control.
Geriatric Use
No dosage adjustment is required based on age; however, because JANUMET is substantially excreted by the kidney, it may be useful to assess renal function in elderly patients before initiation of JANUMET and periodically thereafter.
Pregnancy
There are no adequate and well-controlled studies in pregnant women. Therefore, JANUMET should be used during pregnancy only if clearly needed.
Merck & Co., Inc., maintains a registry to monitor the pregnancy outcomes of women exposed to JANUMET while pregnant. Health care providers are encouraged to report any prenatal exposure to JANUMET by calling the Pregnancy Registry at 1-800-986-8999.
Nursing Mothers
No studies in lactating animals have been conducted with the combined components of JANUMET. Because many drugs are excreted in human milk, caution should be exercised when JANUMET is administered to a nursing woman.
Pediatric
Safety and effectiveness of JANUMET in children under 18 years have not been established.
To assess the glycemic efficacy and safety of JANUMET in patients with type 2 diabetes who had inadequate glycemic control on metformin monotherapy.
A 24-week, multinational, randomized, double-blind, parallel-group, placebo-controlled study with 701 patients, who after a screening diet and exercise run-in period, a metformin dose-adjustment and stabilization period, and a 2-week, single-blind, placebo run-in period, were randomized to receive either JANUMET or metformin plus placebo. Patients who did not meet specific glycemic goals during the studies were treated with pioglitazone rescue therapy.
Men and women aged 19 to 78 years with mild to moderate hyperglycemia (A1C >7% and <10% [mean A1C 8%]).
Patients with type 1 diabetes, a history of ketoacidosis, acute or rapidly progressive renal disease, or a history of renal transplant were excluded from this trial.
Primary: A1C change from baseline compared with placebo at Week 24 and safety and tolerability compared with placebo.
Secondary: Change in FPG from baseline to Week 24 compared with placebo and in glucose, insulin, and C peptide measured immediately before and at 60 and 120 minutes after a meal compared with placebo.
In a 24-week study of patients with type 2 diabetes inadequately controlled on metformin alone: