metformin + sitagliptin: clinical use

Prescribing considerations

• Confirm the fixed combination matches the required amounts of both components; use separate components when independent adjustment is necessary.
• Review renal function and lactic-acidosis risk before initiation and during acute illness, dehydration, surgery or contrast imaging.
• The product is for adults with type 2 diabetes and is not appropriate for type 1 diabetes or diabetic ketoacidosis.

Contraindications and cautions

• Hypersensitivity to either active substance or an excipient.
• Acute metabolic acidosis, diabetic ketoacidosis or diabetic pre-coma.
• Severe renal impairment with GFR below 30 mL/min.
• Acute conditions likely to impair renal function, including dehydration, severe infection, shock or intravascular iodinated contrast exposure.
• Conditions causing tissue hypoxia, including decompensated cardiac or respiratory failure, recent myocardial infarction or shock.
• Hepatic impairment, acute alcohol intoxication or alcoholism.
• Pregnancy and breastfeeding for the selected fixed product.

Monitoring

• Check GFR before treatment and at least annually; assess more often in older people or those at risk of renal decline.
• Monitor glycaemic control and hypoglycaemia risk, particularly with insulin or sulphonylureas.
• Test vitamin B12 when deficiency is suspected and consider periodic testing in people with risk factors.
• During significant acute illness, assess promptly for ketoacidosis, lactic acidosis and deterioration in renal function.

Clinical pharmacology

Sitagliptin selectively inhibits DPP-4, increasing active GLP-1 and GIP and producing glucose-dependent effects on insulin and glucagon. Metformin reduces hepatic glucose production and improves insulin sensitivity. Both are cleared predominantly through the kidneys; the fixed tablet is bioequivalent to co-administration of its individual components.

Formulation and product differences

• The selected product is a red, oval film-coated fixed-combination tablet marked “MS” and “31”.
• It is essentially sodium-free.
• A fixed combination may be unsuitable where the two components need to be adjusted independently.

Tablet

Route: Oral

Strengths: 50 mg + 1000 mg, 50 mg + 850 mg