JANUMET
Clinical safety rating: caution
Comprehensive clinical and safety monograph for JANUMET (JANUMET).
Janumet is a combination of sitagliptin, a DPP-4 inhibitor, and metformin, a biguanide. Sitagliptin increases incretin levels (GLP-1, GIP), enhancing insulin secretion and decreasing glucagon secretion in a glucose-dependent manner. Metformin decreases hepatic glucose production, decreases intestinal absorption of glucose, and improves insulin sensitivity by increasing peripheral glucose uptake and utilization.
| Metabolism | Sitagliptin is primarily excreted unchanged in urine via active tubular secretion, with minor metabolism via CYP3A4 and CYP2C8. Metformin is not metabolized and is excreted unchanged in urine by tubular secretion. |
| Excretion | Sitagliptin: 87% renal (unchanged), 13% fecal (metabolites). Metformin: 90-100% renal (unchanged), <5% fecal. |
| Half-life | Sitagliptin: 12.4 hours (terminal). Clinical context: supports once-daily dosing, but half-life increases in renal impairment. Metformin: 6.2 hours (terminal). Shorter half-life requires multiple daily dosing; prolonged in renal impairment. |
| Protein binding | Sitagliptin: 38% (albumin). Metformin: negligible (<5%). |
| Volume of Distribution | Sitagliptin: 198 L (≈2.8 L/kg for 70 kg). Metformin: 654 L (≈9.3 L/kg for 70 kg). Clinical meaning: Metformin Vd indicates extensive tissue distribution, predominantly in gastrointestinal tissues and red blood cells. |
| Bioavailability | Sitagliptin: 87% (oral). Metformin: 50-60% (oral), variable with food. |
| Onset of Action | Sitagliptin: 1-3 hours (time to peak inhibition of DPP-4). Metformin: 2-3 hours (peak effect on glucose lowering). Oral route. |
| Duration of Action | Sitagliptin: >24 hours (DPP-4 inhibition sustained). Metformin: 8-12 hours (glucose-lowering effect). Clinical note: Metformin duration shorter, but combination product administered twice daily. |
Initial dose: 50 mg sitagliptin/500 mg metformin hydrochloride twice daily orally with meals. Dose may be increased up to 50 mg sitagliptin/1000 mg metformin twice daily based on glycemic response and tolerability.
| Dosage form | TABLET |
| Renal impairment | Contraindicated if eGFR <30 mL/min/1.73 m2. eGFR 30-45: do not initiate; if already on therapy, reduce dose to 25 mg sitagliptin/500 mg metformin once daily. eGFR 45-60: maximum dose 50 mg sitagliptin/1000 mg metformin twice daily. Monitor renal function. |
| Liver impairment | Contraindicated in patients with hepatic impairment (Child-Pugh class A, B, or C) due to metformin component risk of lactic acidosis. |
| Pediatric use | Not approved for use in pediatric patients (<18 years). Safety and efficacy not established. |
| Geriatric use | Use with caution; monitor renal function closely. Initiate at lowest dose (25 mg sitagliptin/500 mg metformin) and titrate slowly. Avoid in patients aged ≥80 years unless normal renal function confirmed. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for JANUMET (JANUMET).
| Breastfeeding | Sitagliptin is excreted in rat milk; unknown in humans. Metformin is excreted into human milk at low levels with an estimated infant dose of 0.18-0.4 mg/kg/day (M/P ratio ~0.35-0.65). Due to potential for hypoglycemia and uncertain long-term effects, breastfeeding is not recommended during Janumet therapy. |
| Teratogenic Risk | Janumet (sitagliptin/metformin) is classified as FDA Pregnancy Category B for sitagliptin and Category B for metformin. Animal studies show no evidence of teratogenicity, but there are no adequate well-controlled studies in pregnant women. Risk cannot be ruled out. Metformin crosses the placenta and may cause fetal lactic acidosis in third trimester. Generally, insulin is preferred for gestational diabetes management. |
■ FDA Black Box Warning
Lactic acidosis: Metformin hydrochloride can cause lactic acidosis, a rare but serious condition. If suspected, discontinue Janumet and treat promptly.
| Common Effects | Hypoglycemia low blood glucose level Nausea Vomiting Diarrhea Decreased appetite Abdominal bloating Upper respiratory tract infection |
| Serious Effects |
["Severe renal impairment (eGFR <30 mL/min/1.73 m²)","Acute or chronic metabolic acidosis (including diabetic ketoacidosis)","History of serious hypersensitivity reaction to Janumet or its components","Use of iodinated contrast agents with eGFR <60 mL/min/1.73 m² or liver disease, alcohol abuse, or conditions altering renal function"]
| Precautions | ["Lactic acidosis risk (sepsis, dehydration, hepatic impairment, alcohol abuse, unstable CHF, radiologic contrast studies)","Pancreatitis (discontinue if suspected)","Hypoglycemia (especially with sulfonylurea or insulin coadministration)","Renal impairment (assess renal function before initiation and periodically; contraindicated if eGFR <30 mL/min/1.73 m²)","Vitamin B12 deficiency (monitor levels with long-term metformin use)","Hypersensitivity reactions (e.g., anaphylaxis, angioedema, Stevens-Johnson syndrome)","Heart failure (monitor for signs; cardiovascular outcome trials showed no increased risk with saxagliptin, but caution with DPP-4 inhibitors)"] |
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| Fetal Monitoring | Monitor maternal blood glucose, renal function (serum creatinine), and lactic acidosis signs. Fetal monitoring includes ultrasound for growth, and fetal heart rate monitoring in third trimester if glycemic control is suboptimal. Assess for neonatal hypoglycemia after delivery. |
| Fertility Effects | Metformin may improve fertility in women with PCOS by restoring ovulation. No negative effects on male or female fertility reported. No specific fertility studies with sitagliptin component; animal studies show no impairment. |