Fixed_Dose-Sitagliptin /metformin

• Sitagliptin/Metformin XR is indicated as an adjunct to healthy eating and physical activity to improve glycaemic management in adults with type 2 diabetes mellitus when treatment with both sitagliptin and metformin is appropriate.

For the latest PBS indications for Sitagliptin/Metformin XR please see
https://www.pbs.gov.au/medicine/item/10089b-10090c-9449h-9450j-9451k

Life threatening lactic acidosis can occur due to accumulation of metformin. The main risk factor is renal impairment, other risk factors include old age associated with reduced renal function and high doses of metformin above 2g per day.

• The dosage of antihyperglycemic therapy with Sitagliptin/Metformin XR should be individualised on the basis of a person’s current regimen, effectiveness and tolerability while not exceeding the maximum recommended daily dose of 100 mg sitagliptin and 2000 mg metformin. (Person centred care)
• Sitagliptin/Metformin XR should be given once daily with a meal preferably in the evening. The dose should be escalated gradually to reduce the gastrointestinal (GI) side effects due to metformin. Additionally, administration of Sitagliptin/Metformin XR with food enhances plasma concentrations of metformin.
• To preserve the modified-release properties, the tablets must not be split, broken, crushed, or chewed before swallowing. There have been reports of incompletely dissolved Sitagliptin/Metformin XR tablets being eliminated in the faeces. It is not known whether this material seen in faeces contains active drug. If an individual reports repeatedly seeing tablets in faeces, the healthcare provider should assess adequacy of glycaemic management.

As initial therapy:
– For individuals with type 2 diabetes mellitus, whose hyperglycaemia is inadequately managed with healthy eating and physical activity, when dual therapy is appropriate, the recommended total daily starting dose of Sitagliptin/Metformin XR is 100 mg sitagliptin and 1000 mg metformin. Individuals with inadequate glycaemic management on this dose should have their metformin dose increased up to a maximum of 100 mg sitagliptin/2000 mg metformin daily.

For individuals inadequately managed on sitagliptin monotherapy:
– For those whose diabetes is inadequately on sitagliptin alone, the recommended starting dose of Sitagliptin/Metformin XR is 100 mg sitagliptin and 1000 mg metformin daily. Individuals may be titrated up to 100 mg sitagliptin/2000 mg metformin daily to achieve healthy glycaemia. Individuals taking sitagliptin monotherapy dose-adjusted for renal impairment should not be switched to Sitagliptin/Metformin XR.

For individuals, whose diabetes is inadequately managed on metformin monotherapy:
– For those whose diabetes is not adequately managed on metformin alone, the usual starting dose of Sitagliptin/Metformin XR should provide sitagliptin 100 mg total daily dose plus the dose of metformin already being taken.

For individuals switching from sitagliptin co-administered with metformin:
– For individuals switching from sitagliptin co-administered with metformin, Sitagliptin/Metformin XR may be initiated at the dose of sitagliptin, and metformin already being taken.

For individuals who diabetes is inadequately managed on dual combination therapy with metformin and a sulfonylurea:
– The usual starting dose of Sitagliptin/Metformin XR should provide sitagliptin 100 mg total daily dose and the dose of metformin already being taken. Individuals may require lower sulfonylurea doses to reduce the risk of sulfonylurea-induced hypoglycaemia.

For individuals, whose diabetes is inadequately managed on dual combination therapy with metformin and insulin: – The usual starting dose of Sitagliptin/Metformin XR should provide 100 mg total daily dose of sitagliptin. In determining the starting dose of the metformin component, an individual’s level of glycaemia and current dose of metformin should be considered. Individuals currently on or initiating insulin therapy may require lower doses of insulin to reduce the risk of hypoglycaemia

• Renal impairment: No dose adjustment is needed in mild renal impairment (estimated glomerular filtration rate [eGFR] ≥ 60 mL/min/1.73 m2). An eGFR should be assessed before initiation of treatment with Sitagliptin/Metformin XR and at least annually thereafter. In those at increased risk of further progression of renal impairment and in the elderly, renal function should be assessed more frequently, e.g., every 3-6 months.
• Factors that may increase risk of lactic acidosis should be reviewed before considering initiation of metformin in those with eGFR < 60 mL/min/1.73 m2. Sitagliptin/Metformin XR is prescribed once daily. Sitagliptin/Metformin XR is contraindicated in those with eGFR < 30 mL/min/1.73 m2 Discontinue Sitagliptin/Metformin XR if the eGFR later falls below 30 mL/min/1.73 m2 Initiation of Sitagliptin/Metformin XR in individuals with an eGFR ≥ 30 mL/min/1.73 m2 and < 45 mL/min/1.73 m2 is not recommended. In those taking Sitagliptin/Metformin XR whose eGFR later falls below 45 mL/min/1.73 m2 the benefit and risk of continuing therapy should be assessed and dose of the sitagliptin component limited to 50 mg once day.

• Hepatic Impairment- Sitagliptin is primarily renally eliminated, severe hepatic impairment is not expected to affect the pharmacokinetics of sitagliptin.
  -Metformin: No pharmacokinetic studies of metformin have been conducted in those with hepatic impairment. Impaired hepatic function has been associated with some cases of lactic acidosis in those taking metformin, however.
• Sitagliptin/Metformin XR should be temporarily discontinued in those undergoing radiological studies involving intravascular administration of iodinated contrast materials, because the use of such products may result in acute alteration of renal function.

JANUMET XR are not currently indicated for use in children below 18 years.

• Severe renal impairment (eGFR < 30 mL/min/1.73 m2)
• Known hypersensitivity to sitagliptin or metformin
• Acute or chronic metabolic acidosis, including ketoacidosis, with or without coma.

• General – Sitagliptin/Metformin XR should not be used in individuals with type 1 diabetes mellitus.
• Metformin
  -Lactic acidosis: Lactic acidosis is a rare, but serious metabolic complication that can occur due to metformin accumulation during treatment with metformin. When it occurs, it is fatal in approximately 50% of cases. Lactic acidosis is a medical emergency and must be treated in hospital immediately. The risk of lactic acidosis increases with the degree of renal dysfunction. Reported cases of lactic acidosis in individuals on metformin have occurred primarily in those with diabetes with significant renal insufficiency, often in the setting of multiple concomitant medical/surgical problems and multiple concomitant medications. Special caution should be taken in the elderly due to the decrease of renal function with age.
Note: Diabetes MedsCheck for referral to healthcare team for education on lactic acidosis. -Surgery: Metformin must be discontinued at the time of surgery under general, spinal or epidural anaesthesia. Therapy may be restarted no earlier than 48 hours following surgery or resumption of oral nutrition and provided that renal function has been re-evaluated and found to be stable.
• Monitoring of renal function: Renal function should be confirmed before initiation of Sitagliptin/Metformin XR therapy, and then at least once a year in those with normal renal function and at least two to four times a year if serum creatinine levels are at or above the upper limit of normal and in elderly individuals. Decreased renal function in the elderly is frequent and asymptomatic. Special caution should be exercised in situations where renal function may become impaired, for example when initiating antihypertensive or diuretic therapy or when starting treatment with a nonsteroidal anti-inflammatory drug (NSAID).
Note: Diabetes MedsCheck with referral for annual cycle of care.
• Alcohol Intake: Alcohol is known to potentiate the effect of metformin on lactate metabolism. Individuals, therefore, should be warned against excessive alcohol intake while receiving Sitagliptin/Metformin XR.

• Metformin
  -Gastrointestinal disorders: Gastrointestinal symptoms such as nausea, vomiting, diarrhoea, abdominal pain, and loss of appetite are very common (>10%): these occur most frequently during initiation of therapy and resolve spontaneously in most cases. To prevent these gastrointestinal symptoms, it is recommended that this medicinal product be taken in 2 or 3 daily doses. A slow increase of the dose may also improve gastrointestinal tolerability.
  -Metabolism and nutrition disorders: Lactic acidosis is a very rare (<0.01%) but serious metabolic complication that can occur due to metformin accumulation during treatment with metformin. The onset of lactic acidosis is often subtle and accompanied only by non-specific symptoms such as malaise, myalgia, respiratory distress, increasing somnolence and non-specific abdominal distress. There may be associated hypothermia, hypotension and resistant bradyarrhythmias with more marked acidosis. Note: Diabetes MedsCheck with referral to healthcare team for education on lactic acidosis.
  -Hepatobiliary disorders: Very rare: liver function test abnormalities or hepatitis requiring treatment discontinuation.
  -Skin and subcutaneous tissue disorders: Skin reactions such as erythema, pruritus and urticaria have been reported but the incidence is very rare (<0.01%).
  -Nervous system disorders -Taste disturbance (3 %) is common.
  -Vitamin B12 Levels: In controlled, 29-week clinical trials of immediate release metformin, a decrease to subnormal levels of previously normal serum Vitamin B12 levels, without clinical manifestations, was observed in approximately 7% of people with diabetes. Such decrease, possibly due to interference with B12 absorption from the B12-intrinsic factor complex is, however, very rarely associated with anaemia and appears to be rapidly reversible with discontinuation of metformin or Vitamin B12 supplementation. Measurement of haematologic parameters on an annual basis is advised in people with diabetes on Sitagliptin/Metformin XR 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). See interventions for further information.