Janumet

Janumet is a fixed-dose combination tablet containing two antidiabetic medicines: sitagliptin (a dipeptidyl peptidase-4 inhibitor, or DPP-4 inhibitor) and metformin hydrochloride. It is used to improve blood glucose control in adults with type 2 diabetes as an adjunct to diet and exercise, when treatment with both sitagliptin and metformin is appropriate.

Dual Mechanism of Action

Sitagliptin inhibits the enzyme DPP-4, which normally breaks down incretin hormones (GLP-1 and GIP). By preventing this breakdown, sitagliptin increases incretin levels, which stimulate insulin release from beta cells when blood glucose is elevated and reduce glucagon secretion from alpha cells. This glucose-dependent mechanism means sitagliptin has a low risk of hypoglycaemia as monotherapy. Metformin reduces hepatic glucose production (gluconeogenesis) and improves peripheral insulin sensitivity.

Combination Benefit

Janumet combines these complementary mechanisms in a single tablet, improving compliance and potentially offering better blood glucose control than either agent alone. This fixed-dose combination is appropriate for patients who are already stabilised on both components separately.

How to Take Janumet

Take Janumet twice daily with meals to reduce gastrointestinal side effects from the metformin component. Swallow tablets whole with water, do not crush or split them. Take at the same times each day for consistent blood glucose control.

Common regimens include Janumet 50 mg/850 mg or 50 mg/1000 mg twice daily. The total daily sitagliptin dose should not exceed 100 mg (50 mg twice daily). The metformin dose is adjusted according to kidney function and tolerability, up to a maximum of 2550 mg daily. Your prescriber will determine the most suitable combination for you.

Janumet tablets are available in three strengths: sitagliptin 50 mg/metformin 850 mg, sitagliptin 50 mg/metformin 1,000 mg, and Janumet XR (extended-release) formulations. Take twice daily with meals. Renal function must be checked before starting and regularly thereafter; dose adjustment or discontinuation is required if eGFR falls below 45 mL/min/1.73m².

Common Side Effects

The most frequently reported side effects from the metformin component are gastrointestinal: nausea, diarrhoea, abdominal pain, and a metallic taste. These are most common at the start of treatment and with dose increases, and usually improve over time. Taking Janumet with food reduces these effects.

Sitagliptin-Related Effects

Upper respiratory tract infections, nasopharyngitis, and headache are associated with sitagliptin. Rare but serious side effects include pancreatitis (reported with DPP-4 inhibitors; symptoms include persistent severe abdominal pain radiating to the back) and joint pain (arthralgia), which may be severe. Report persistent joint pain to your prescriber. Bullous pemphigoid, a blistering skin condition, has been reported rarely with sitagliptin; seek medical attention for any unusual skin blistering.

Janumet should be temporarily stopped before and after procedures using iodinated contrast media. It should be withheld during acute illness causing vomiting, diarrhoea, or dehydration. Monitor renal function regularly; contraindicated if eGFR < 30 mL/min. Stop immediately and seek urgent medical advice if pancreatitis is suspected. Caution in patients with a history of pancreatitis. Lactic acidosis risk is the same as for metformin alone (see metformin warnings).

Contraindicated in patients with eGFR below 30 mL/min/1.73m², metabolic acidosis, diabetic ketoacidosis, severe hepatic impairment, severe renal impairment, and known hypersensitivity to sitagliptin, metformin, or any excipient. Not for use in type 1 diabetes. Caution in patients with a history of pancreatitis.