1. Clinical Overview
A fixed-dose combination (FDC) oral antidiabetic agent containing sitagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, and metformin, a biguanide. This combination provides complementary mechanisms of action to improve glycemic control in type 2 diabetes mellitus (T2DM) by enhancing incretin activity and reducing hepatic glucose production while improving insulin sensitivity. It is indicated when metformin monotherapy is insufficient.
| Onset | Duration | Bioavailability |
|---|---|---|
| Sitagliptin: Plasma DPP-4 inhibition occurs within 15-30 minutes. Metformin: Glucose-lowering effect begins within hours. | Sitagliptin: ~24 hours (allows once-daily dosing). Metformin: 12-24 hours (dose-dependent). | Sitagliptin: ~87%. Metformin: 50-60%. |
2. Mechanism of Action
Sitagliptin selectively inhibits the enzyme dipeptidyl peptidase-4 (DPP-4), which degrades the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). This inhibition increases active incretin levels, stimulating glucose-dependent insulin release from pancreatic beta cells and suppressing glucagon secretion from alpha cells. Metformin decreases hepatic gluconeogenesis, reduces intestinal glucose absorption, and improves peripheral glucose uptake and utilization by increasing insulin sensitivity.
3. Indications & Uses
- Type 2 Diabetes Mellitus as an adjunct to diet and exercise to improve glycemic control in adults inadequately controlled on metformin monotherapy.
- Type 2 Diabetes Mellitus as an adjunct to diet and exercise in patients already treated with the combination of sitagliptin and metformin as separate tablets.
4. Dosage & Administration
Adult Dosage: One tablet twice daily with meals. The maximum recommended daily dose of sitagliptin is 100 mg and of metformin is 2000 mg. This FDC provides 100 mg sitagliptin and 2000 mg metformin per day when taken as prescribed.
Administration: Take with meals to reduce gastrointestinal side effects from metformin. Swallow whole with a glass of water. Do not crush or chew.
5. Side Effects
Common side effects may include:
- Nausea
- Diarrhea
- Abdominal discomfort
- Flatulence
- Headache
- Upper respiratory tract infection
- Hypoglycemia (when used with sulfonylureas/insulin)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Cimetidine | Increases metformin plasma concentration by reduced renal tubular secretion. | Moderate |
| Furosemide | May increase metformin concentration; monitor glucose control. | Moderate |
| Iodinated Contrast Media | Risk of lactic acidosis and acute renal failure. Discontinue metformin before procedure. | High |
| Alcohol | Potentiates metformin's effect on lactate metabolism; increases risk of lactic acidosis. | High |
| Sulfonylureas (e.g., Glimepiride) or Insulin | Increased risk of hypoglycemia. May require dose reduction of sulfonylurea/insulin. | Moderate |
| Digoxin | Slight increase in digoxin AUC reported with sitagliptin; monitor digoxin levels. | Low |
| Carbonic Anhydrase Inhibitors (e.g., Topiramate) | May increase risk of lactic acidosis; monitor. | Moderate |
7. Patient Counselling
- DO take the tablet twice daily with meals to reduce stomach upset.
- DO continue your diet and exercise plan as advised by your doctor.
- DO monitor your blood glucose levels regularly as instructed.
- DO inform all your doctors and the radiologist that you are taking this medicine before any surgery or scan with contrast dye.
- DO report any unexplained muscle pain, breathing difficulty, stomach pain, or feeling cold.
- DO NOT take this medicine if you have severe kidney problems.
- DO NOT consume excessive alcohol.
- DO NOT stop taking this medicine without consulting your doctor, even if you feel well.
8. Toxicology & Storage
Overdose: Sitagliptin: In clinical studies, doses up to 800 mg produced no adverse effects. Expected: hypoglycemia (if combined with other agents), headache, GI disturbance. Metformin: Overdose has been associated with lactic acidosis, which is a medical emergency. Symptoms include vomiting, diarrhea, abdominal pain, hypothermia, hypotension, and bradycardia.
Storage: Store below 30°C. Protect from light and moisture. Keep in the original blister pack or container. Keep out of reach of children.