JANUMET XR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for JANUMET XR (JANUMET XR).
JANUMET XR is a combination of sitagliptin, a DPP-4 inhibitor, and metformin, a biguanide. Sitagliptin increases active incretin levels (GLP-1, GIP), enhancing glucose-dependent insulin secretion and reducing glucagon secretion. Metformin decreases hepatic glucose production, reduces intestinal glucose absorption, and improves insulin sensitivity.
| Metabolism | Sitagliptin: primarily renal excretion (70-80% unchanged), minimal hepatic metabolism via CYP3A4 and CYP2C8. Metformin: excreted unchanged in urine; no hepatic metabolism. |
| Excretion | Sitagliptin: ~79% excreted unchanged in urine via renal tubular secretion (active secretion) and glomerular filtration; ~13% undergoes hepatic metabolism; ~1% excreted in feces. Metformin: ~90% excreted unchanged in urine via active tubular secretion. |
| Half-life | Sitagliptin: terminal half-life ~12.4 hours, allowing once-daily dosing. Metformin: terminal half-life ~6.2 hours in plasma, increased to ~17.6 hours in renal impairment. |
| Protein binding | Sitagliptin: ~38% bound to plasma proteins. Metformin: negligible (<5%) protein binding. |
| Volume of Distribution | Sitagliptin: Vd ~198 L (approximately 2.8 L/kg for a 70 kg individual), indicating extensive tissue distribution. Metformin: Vd 654 ± 358 L (9.3 L/kg), widely distributed into erythrocytes and tissues. |
| Bioavailability | Sitagliptin: oral bioavailability ~87%. Metformin: oral absolute bioavailability ~50-60% for immediate-release, reduced under fed conditions; Janumet XR provides extended-release profile. |
| Onset of Action | Sitagliptin: DPP-4 inhibition reaches near-maximum within 1-2 hours. Metformin: reduction in fasting plasma glucose begins within 1-2 days; full effect by 1-2 weeks. |
| Duration of Action | Sitagliptin: DPP-4 inhibition >80% at 24 hours. Metformin: glucose-lowering effect persists for 24 hours with extended-release formulation. |
| Molecular Weight | Metformin: 129.16 Da; Sitagliptin: 407.31 Da |
| Brand Substitutes | Sitawok M 500 Tablet, Istamet 50mg/500mg Tablet, Sitanorm M 50mg/500mg Tablet, Ignalis-M IR 50/500 Tablet, Sitaglyn M IR 50/500 Tablet, Sitamax M 50mg/1000mg Tablet, SitaOD Met 50/1000 Tablet, Siglyn M IR 50/1000 Tablet, Lupisit M 50mg/1000mg Tablet, Sitenali M 50mg/1000mg Tablet |
One tablet orally once daily, with evening meal; initial dose based on patient's current sitagliptin and metformin doses, or new patients: starting dose 50 mg sitagliptin/500 mg metformin XR; maximum dose 100 mg sitagliptin/2000 mg metformin XR per day.
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | eGFR ≥45 mL/min/1.73m²: no adjustment. eGFR 30-44 mL/min/1.73m²: maximum dose 50 mg sitagliptin/1000 mg metformin XR daily. eGFR <30 mL/min/1.73m² or ESRD: contraindicated (metformin component). |
| Liver impairment | Contraindicated in patients with hepatic impairment (Child-Pugh score not specified; avoid due to metformin component risk of lactic acidosis). |
| Pediatric use | Not recommended for pediatric patients under 18 years of age due to lack of data. |
| Geriatric use | Cautious dose titration; renal function should be assessed before initiation and monitored regularly. Avoid initiation if eGFR <45 mL/min/1.73m². |
| 1st trimester | Limited data; metformin and sitagliptin cross placenta. Avoid unless clearly needed. |
| 2nd trimester | Use only if benefit outweighs risk; monitor fetal growth and amniotic fluid. |
| 3rd trimester | Avoid prolonged use; may cause neonatal hypoglycemia. |
Clinical note
Comprehensive clinical and safety monograph for JANUMET XR (JANUMET XR).
| Placental transfer | Metformin and sitagliptin cross the placenta. Metformin shows dose-dependent transfer; sitagliptin transfer is limited but present. |
| Breastfeeding | Metformin and sitagliptin are excreted in human milk. Limited data; caution advised. Monitor infant for hypoglycemia and gastrointestinal effects. |
| Lactation Rating |
■ FDA Black Box Warning
Lactic acidosis: Rare but serious risk due to metformin accumulation; risk increases with renal impairment, sepsis, dehydration, hepatic impairment, acute heart failure, and alcohol use. Discontinue if acidosis suspected.
| Serious Effects |
Renal impairment (eGFR <30 mL/min/1.73 m²)Acute or chronic metabolic acidosis (including diabetic ketoacidosis)Hypersensitivity to metformin, sitagliptin, or components
| Precautions | Lactic acidosis risk: monitor renal function, avoid in eGFR <30 mL/min/1.73m2, hold prior to iodinated contrast procedures, Pancreatitis (sitagliptin): monitor for signs; discontinue if suspected, Acute kidney injury: monitor renal function, Hypoglycemia: may occur when combined with insulin or sulfonylureas, Vitamin B12 deficiency: metformin may reduce absorption; monitor periodically, Hypersensitivity reactions: angioedema, Stevens-Johnson syndrome reported with sitagliptin |
| Food/Dietary | Take with evening meal to reduce metformin GI effects. Avoid excessive alcohol intake (acute or chronic) due to increased risk of lactic acidosis. No specific food restrictions; maintain a diabetes-appropriate diet. |
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| Teratogenic Risk | Janumet XR contains sitagliptin and metformin. Metformin is associated with fetal hypoxia and acidosis risk due to lactic acidosis in third trimester; limited human data show no increased major malformations. Sitagliptin: animal studies show fetal toxicity at high doses; no adequate human studies. First trimester: risk cannot be excluded; second/third trimester: avoid if possible due to metformin's effects on fetal glucose metabolism. |
| Fetal Monitoring | Monitor renal function, serum creatinine, and liver function tests before and during therapy. Monitor blood glucose and HbA1c. Fetal monitoring: ultrasound for growth and anomalies as per standard obstetric care. Watch for signs of lactic acidosis (maternal) and neonatal hypoglycemia. |
| Fertility Effects | Metformin may improve ovulation in women with polycystic ovary syndrome due to insulin sensitization. No known negative effects on spermatogenesis in males; sitagliptin no known adverse effects on fertility in animal studies. |
| Clinical Pearls | Janumet XR combines sitagliptin (DPP-4 inhibitor) and extended-release metformin. Extended-release formulation reduces GI side effects compared to immediate-release metformin. Contraindicated in eGFR <30 mL/min/1.73m²; check renal function before initiation and annually. Discontinue for iodinated contrast procedures; hold metformin at time of or before procedure and restart after 48 hours if renal function stable. May cause acute pancreatitis; monitor for abdominal pain. Risk of lactic acidosis with metformin; avoid in hypoxic states, hepatic impairment, alcohol abuse. VIP: Elderly patients or those on diuretics/ACEi/ARB at risk for renal impairment; monitor vitamin B12 levels long-term. |
| Patient Advice | Take once daily with the evening meal to reduce GI upset from metformin. Swallow tablet whole; do not crush, chew, or cut. · Do not exceed 2 tablets per day. Missed dose: skip if almost time for next dose; do not double. · Stop taking and contact doctor immediately if signs of pancreatitis: severe abdominal pain that may radiate to back, nausea/vomiting. · Report symptoms of lactic acidosis: muscle pain, weakness, trouble breathing, unusual sleepiness, abdominal pain, nausea/vomiting,dizziness, low body temperature, slow heart rate. · Monitor blood sugar regularly as directed. Maintain adequate hydration. Inform all providers you are taking this medication, especially before surgery or contrast dye procedures. · Limited alcohol intake: excessive alcohol may increase risk of lactic acidosis; avoid binge drinking or chronic heavy use. |