SITAGLIPTIN AND METFORMIN HCL
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 and GIP), leading to glucose-dependent insulin secretion and decreased 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; minimal hepatic metabolism via CYP3A4 and CYP2C8. Metformin: Not metabolized; excreted unchanged in urine via tubular secretion. |
| Excretion | Sitagliptin: 79% excreted unchanged in urine via active tubular secretion and glomerular filtration; 13% metabolized with minimal biliary/fecal elimination (1% unchanged in feces). Metformin: 90% excreted unchanged in urine via active tubular secretion; 0% biliary/fecal. |
| Half-life | Sitagliptin: terminal t1/2 12.4 hours; Metformin: terminal t1/2 6.2 hours (prolonged to 17.6 hours in renal impairment). Combination: effective t1/2 ~7-12 hours, dosing adjusted for CrCl <45 mL/min. |
| Protein binding | Sitagliptin: 38% bound (albumin). Metformin: negligible (<5% bound) to plasma proteins. |
| Volume of Distribution | Sitagliptin: Vd 198 L (2.5 L/kg for 80 kg) indicating extensive tissue distribution. Metformin: Vd 654±358 L (8.2 L/kg) indicating high tissue uptake, primarily erythrocytes and gastrointestinal tract. |
| Bioavailability | Sitagliptin: 87% oral bioavailability. Metformin: 50-60% oral bioavailability (immediate-release). Extended-release: 50-60% with food reducing Cmax. |
| Onset of Action | Oral: Sitagliptin onset ~1-2 hours (DPP-4 inhibition); Metformin onset ~2-3 hours (decreased hepatic glucose production). Peak effect at 1-2 weeks for glycemic control. |
| Duration of Action | Sitagliptin: >24 hours, once-daily dosing; Metformin: 12-24 hours, immediate-release twice daily or extended-release once daily. Clinical glucose-lowering persists for 24 hours with combination. |
Initial: 50 mg sitagliptin/500 mg metformin twice daily or 50 mg/1000 mg twice daily (max 100 mg/2000 mg per day). Dose adjusted gradually based on glycemic response and tolerability.
| Dosage form | TABLET |
| Renal impairment | eGFR ≥45 mL/min/1.73 m²: no adjustment. eGFR 30-44: maximum 50 mg sitagliptin/1000 mg metformin daily (use low-dose combination). eGFR <30: contraindicated. |
| Liver impairment | Child-Pugh Class C: contraindicated due to metformin. Child-Pugh A or B: possible limited data, avoid in severe hepatic impairment. |
| Pediatric use | Not recommended for use in pediatric patients (<18 years) due to lack of safety and efficacy data. |
| Geriatric use | Start at lower doses (e.g., 25 mg/500 mg twice daily) and titrate slowly. Monitor renal function (eGFR) frequently, as elderly are more prone to renal impairment and lactic acidosis. |
| 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 | Sitagliptin: Unknown if excreted in human breast milk; limited data suggest low levels. Metformin: Excreted in breast milk with M/P ratio approximately 0.35 (range 0.11-1.0). Infant exposure is estimated at about 0.5% of maternal weight-adjusted dose. Considered compatible with breastfeeding; monitor infant for hypoglycemia and gastrointestinal effects. |
| Teratogenic Risk |
■ FDA Black Box Warning
Lactic acidosis: Metformin accumulation can cause lactic acidosis, a rare but serious complication; risk factors include renal impairment, sepsis, dehydration, and alcohol abuse.
| Common Effects | Nasopharyngitis |
| Serious Effects |
Severe renal impairment (eGFR < 30 mL/min/1.73 m²); acute or chronic metabolic acidosis; diabetic ketoacidosis; history of hypersensitivity to sitagliptin, metformin, or any component of the product; use in patients with type 1 diabetes.
| Precautions | Lactic acidosis risk; acute kidney injury; pancreatitis (acute or worsening); severe and disabling arthralgia; hypoglycemia when used with insulin or sulfonylureas; vitamin B12 deficiency (long-term metformin use); heart failure (if history); hypersensitivity reactions including anaphylaxis, angioedema, and Stevens-Johnson syndrome. |
Loading safety data…
| Sitagliptin: FDA Pregnancy Category B. Animal studies show no evidence of teratogenicity at exposures up to 30 times human exposure. No adequate human studies; risk cannot be excluded. Metformin: FDA Pregnancy Category B. Available human data do not show increased risk of major birth defects or miscarriage. However, third trimester use may be associated with increased risk of neonatal hypoglycemia and transient metabolic acidosis. |
| Fetal Monitoring | Monitor maternal blood glucose, HbA1c, renal function (serum creatinine, BUN), and liver function tests. Assess for lactic acidosis (rare) with metformin especially in renal impairment. Fetal monitoring: Ultrasound for growth and development, consider nonstress test or biophysical profile in third trimester for gestational diabetes or preexisting diabetes. Monitor newborn for hypoglycemia and acidosis after delivery. |
| Fertility Effects | Metformin may improve fertility in women with polycystic ovary syndrome (PCOS) by reducing hyperinsulinemia and improving ovulatory function. No known negative effects on fertility from sitagliptin or metformin in males or females. No human data on sitagliptin specifically; animal studies show no impairment of fertility. |