Short answer: Both tablets pair metformin with a second diabetes drug.12 Janumet adds sitagliptin, a DPP-4 inhibitor; Synjardy adds empagliflozin, an SGLT2 inhibitor. Synjardy also carries heart and kidney uses from empagliflozin and is approved from age 10; Janumet is for adults. Both have a boxed warning for lactic acidosis from metformin. Neither label reports a trial against the other.
| Janumet | Synjardy | |
|---|---|---|
| Paired with metformin | Sitagliptin, a DPP-4 inhibitor1 | Empagliflozin, an SGLT2 inhibitor2 |
| Approved for | Blood sugar control in adults with type 2 diabetes1 | Blood sugar control in adults and children 10 and older with type 2 diabetes; the empagliflozin part also lowers heart death, heart failure hospital stays and kidney decline in certain adults2 |
| How taken | Twice daily with meals1 | Synjardy twice daily with meals; Synjardy XR once daily with a morning meal2 |
| Maximum daily dose | Sitagliptin 100 mg and metformin 2,000 mg1 | Empagliflozin 25 mg and metformin 2,000 mg2 |
| Kidney limits | Not used with an eGFR below 30; not recommended at 30 to under 451 | Not used with an eGFR below 30; starting not recommended below 452 |
| Side effects in label trials | Started with metformin vs placebo: diarrhea 7.5% vs 4.0%, headache 5.9% vs 2.8%1 | Added to metformin and a sulfonylurea: low blood sugar 15.6% on 10 mg vs 9.8% on placebo, urinary tract infection 9.4% vs 6.7%2 |
| Boxed warning | Lactic acidosis1 | Lactic acidosis2 |
The metformin warnings are the same in both: lactic acidosis, and lower vitamin B12, with blood counts checked yearly and B12 every 2 to 3 years.12 The other warnings follow the second drug. Janumet lists pancreatitis, heart failure seen with two other DPP-4 inhibitors, severe joint pain and a blistering skin condition called bullous pemphigoid.1 Synjardy lists ketoacidosis even with blood sugar below 250 mg/dL, fluid loss and low blood pressure, urinary and genital infections including Fournier's gangrene, and lower limb amputation.2 These numbers come from separate trials with different people, lengths and methods, so they are not a head-to-head comparison.
Which, if either, fits is for your prescriber. More detail: Janumet side effects, Synjardy side effects, and the Janumet and Synjardy dosing schedules.