The benefits of empagliflozin in combination with metformin have been shown in 3 main studies involving 1,679 patients with type 2 diabetes whose blood sugar was not adequately controlled by metformin, alone or combined with other diabetes medicines (such as pioglitazone or a type of diabetes medicine called a sulphonylurea). The studies compared the effect of empagliflozin plus metformin versus placebo (a dummy treatment) with metformin. The main measure of effectiveness was the reduction in the level of a substance in the blood called glycosylated haemoglobin (HbA1c) after 24 weeks of treatment. HbA1c gives an indication of how well the blood glucose is controlled.

The studies showed a greater reduction in HbA1c when empagliflozin plus metformin was given, compared with placebo plus metformin. Overall, the additional reduction was 0.58 percentage points with a combination providing 5 mg of empagliflozin twice daily, and 0.62 percentage points with the 12.5 mg dose, and these reductions were considered clinically relevant. Similar benefits were seen in the studies regardless of the other diabetes medicines being taken. In addition, the results indicated that the combination was associated with a beneficial decrease in body weight and blood pressure.

Supportive evidence was provided from several further studies. Some of these were continuations of the main studies that suggested the benefits of the combination continued with longer therapy. Studies also indicated Synjardy was as effective as empagliflozin and metformin taken separately, and that the combination helped reduce HbA1c when added to treatment including insulin.

Another main study showed that adding empagliflozin (one of the active substances of Synjardy) to usual treatment reduced adverse cardiovascular (heart and blood vessels) effects. The study involved patients with type 2 diabetes who already had cardiovascular disease (such as angina, heart attack and stroke). The main measure of effectiveness was the occurrence of one of three major cardiovascular events: stroke, heart attack or death caused by cardiovascular disease. On average, patients in the study were followed up for 3.1 years. In those receiving empagliflozin, cardiovascular events occurred in 10.5% (490 out of 4,687) of patients compared with 12.1% (282 out of 2,333) of patients receiving placebo. Among these, in patients who were also taking metformin (the other active substance in Synjardy), the three major cardiovascular events occurred in 9.9% (344 out of 3,459) of patients receiving empagliflozin and in 10.9% (189 out of 1,734) of patients receiving placebo.