SITAGLIPTIN PHOSPHATE; METFORMIN HYDROCHLORIDE
Clinical safety rating: safe
No significant drug interactions May cause hypersensitivity reactions including anaphylaxis.
Sitagliptin is a dipeptidyl peptidase-4 (DPP-4) inhibitor that increases incretin levels (GLP-1, GIP), enhancing glucose-dependent insulin secretion and decreasing glucagon secretion. Metformin is a biguanide that reduces hepatic glucose production, decreases intestinal glucose absorption, and improves insulin sensitivity.
| Metabolism | Sitagliptin: primarily excreted unchanged in urine via renal tubular secretion; minimal hepatic metabolism via CYP3A4 and CYP2C8. Metformin: not metabolized; excreted unchanged in urine. |
| Excretion | Renal: sitagliptin ~87% unchanged in urine; metformin ~90% unchanged in urine. Biliary/fecal: minimal. |
| Half-life | Sitagliptin: 12.4 h; metformin: 6.2 h (prolonged in renal impairment). |
| Protein binding | Sitagliptin: 38% (albumin); metformin: negligible (<1%). |
| Volume of Distribution | Sitagliptin: ~198 L (2.8 L/kg); metformin: 654±358 L (9.3 L/kg) – extensive tissue distribution. |
| Bioavailability | Sitagliptin: 87% oral; metformin: 50-60% oral (decreased with food). |
| Onset of Action | Sitagliptin: 1-2 h (DPP-4 inhibition peak); metformin: <2 h (reduction in hepatic glucose production). |
| Duration of Action | Sitagliptin: >24 h (once-daily dosing); metformin: 8-12 h (extended release: up to 24 h). |
Oral, 50 mg sitagliptin/500 mg metformin twice daily or 50 mg sitagliptin/1000 mg metformin twice daily, individually titrated based on glycemic response and tolerability. Maximum daily dose: sitagliptin 100 mg, metformin 2000 mg.
| Dosage form | TABLET |
| Renal impairment | eGFR ≥45 mL/min/1.73m²: no adjustment. eGFR 30-44 mL/min/1.73m²: maximum dose 50 mg sitagliptin/500 mg metformin twice daily. eGFR <30 mL/min/1.73m²: contraindicated. |
| Liver impairment | Child-Pugh Class A: no adjustment. Child-Pugh Class B: no data; use with caution. Child-Pugh Class C: contraindicated due to metformin component. |
| Pediatric use | Not approved for pediatric patients under 18 years of age; safety and efficacy not established. |
| Geriatric use | Start at lower end of dosing range due to age-related renal impairment; monitor renal function regularly; avoid in patients with eGFR <30 mL/min/1.73m². |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
No significant drug interactions May cause hypersensitivity reactions including anaphylaxis.
| FDA category | Animal |
| Breastfeeding | Metformin is excreted into breast milk in low amounts (M/P ratio ~0.35); sitagliptin is excreted in animal milk, human data unknown. Caution advised; consider infant monitoring for hypoglycemia. |
| Teratogenic Risk | Pregnancy category X. First trimester: Metformin is not associated with major malformations; sitagliptin animal studies show fetal toxicity at high doses but human data insufficient. Second and third trimesters: Metformin may reduce risk of preeclampsia and macrosomia in gestational diabetes; sitagliptin no adequate human data; combination should be avoided due to lack of safety data. |
■ FDA Black Box Warning
Lactic acidosis associated with metformin accumulation, particularly in patients with renal impairment, acute conditions, or concomitant hepatorenal disease; risk increased with contrast dye studies.
| Common Effects | Nasopharyngitis |
| Serious Effects |
["Severe renal impairment (eGFR < 30 mL/min/1.73 m²)","Acute or chronic metabolic acidosis, including diabetic ketoacidosis","History of hypersensitivity to sitagliptin or metformin","Acute illness or dehydration predisposing to lactic acidosis","Use of iodinated contrast agents (temporary discontinuation)"]
| Precautions | ["Lactic acidosis (metformin)","Pancreatitis (sitagliptin)","Renal impairment: assess renal function before and during therapy","Heart failure risk (sitagliptin)","Hypoglycemia when used with sulfonylureas or insulin","Vitamin B12 deficiency (metformin)"] |
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| Fetal Monitoring | Monitor blood glucose, HbA1c, renal function, liver function, and fetal growth via ultrasound. In pregnancy, monitor for signs of lactic acidosis (unlikely without renal impairment) and neonatal hypoglycemia if used near term. |
| Fertility Effects | Metformin may improve ovulation in women with polycystic ovary syndrome (PCOS); sitagliptin has no known effect on fertility. No data on male fertility effects for the combination. |