ZITUVIMET
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ZITUVIMET (ZITUVIMET).
ZITUVIMET (sitagliptin/metformin) combines sitagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, which increases incretin levels (GLP-1, GIP), enhancing insulin secretion and decreasing glucagon secretion; and metformin, a biguanide that decreases hepatic glucose production, decreases intestinal absorption of glucose, and improves insulin sensitivity by increasing peripheral glucose uptake and utilization.
| Metabolism | Sitagliptin: primarily excreted unchanged in urine (79%), with minor metabolism via CYP3A4 and CYP2C8; Metformin: excreted unchanged in urine, not metabolized. |
| Excretion | Renal: 90% (metformin unchanged), biliary/fecal: 10% (sitagliptin). |
| Half-life | Metformin: ~6.2 hours (prolonged in renal impairment); sitagliptin: ~12.4 hours (allows once-daily dosing). |
| Protein binding | Metformin: negligible (<5%); sitagliptin: 38% (primarily albumin). |
| Volume of Distribution | Metformin: 0.1-0.3 L/kg (low, minimal tissue binding); sitagliptin: 0.4 L/kg (moderate). |
| Bioavailability | Metformin: 50-60% (oral, active absorption); sitagliptin: 87% (oral). |
| Onset of Action | Metformin: Within 2 hours (oral); sitagliptin: Within 1-2 hours (oral). |
| Duration of Action | Metformin: 8-12 hours (glucose-lowering); sitagliptin: ~24 hours (DPP-4 inhibition). |
Zituvimet is a fixed-dose combination tablet containing sitagliptin 50 mg and metformin hydrochloride 500 mg or 1000 mg. Usual adult dose: one tablet (50 mg sitagliptin / 500 mg metformin) twice daily with meals, or one tablet (50 mg sitagliptin / 1000 mg metformin) twice daily with meals, based on patient's current metformin dose. Maximum daily dose: sitagliptin 100 mg, metformin 2000 mg. Route: oral, with meals to reduce gastrointestinal side effects.
| Dosage form | TABLET |
| Renal impairment | Contraindicated if eGFR <30 mL/min/1.73 m². No dose adjustment needed for eGFR ≥60 mL/min/1.73 m². For eGFR 45-59: maximum metformin dose 1000 mg/day; reduce Zituvimet strength accordingly (e.g., use 50/500 strength twice daily only if patient on sitagliptin 100 mg; otherwise consider separate components). For eGFR 30-44: maximum metformin dose 500 mg twice daily; do not initiate; reassess renal function regularly. Discontinue if eGFR declines persistently below 30. |
| Liver impairment | Avoid use in patients with hepatic impairment (Child-Pugh class B or C) due to metformin component. In mild hepatic impairment (Child-Pugh A), no dose adjustment for sitagliptin; use with caution and monitor lactate levels. Metformin is contraindicated in severe hepatic impairment due to risk of lactic acidosis. |
| Pediatric use | Safety and efficacy not established in pediatric patients under 18 years of age. Not recommended. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ZITUVIMET (ZITUVIMET).
| Breastfeeding | Metformin is excreted into breast milk in low amounts (M/P ratio 0.35-0.5); infant dose <0.5% maternal weight-adjusted dose. No adverse effects reported. Sitagliptin: Excreted in animal milk; unknown in humans. Caution recommended. Benefits of breastfeeding likely outweigh minimal risk. |
| Teratogenic Risk | ZITUVIMET (sitagliptin/metformin) is Pregnancy Category B. No evidence of teratogenicity in animal studies. First trimester: Limited human data, but metformin not associated with major malformations. Second and third trimesters: Metformin crosses placenta; minimal risk of neonatal hypoglycemia or adverse outcomes. Sitagliptin: No human pregnancy data; in animal studies, no teratogenicity at 30 times human exposure. Overall, risk appears low but insufficient data. |
■ FDA Black Box Warning
WARNING: LACTIC ACIDOSIS. Metformin hydrochloride can cause lactic acidosis, a rare but serious condition that can be fatal. Symptoms include malaise, myalgias, respiratory distress, increasing somnolence, and nonspecific abdominal distress. Risk factors include renal impairment, concomitant use of certain drugs, age >65 years, radiological studies with contrast, surgery, excessive alcohol intake, hepatic impairment, and hypoxic states. Discontinue metformin if lactic acidosis is suspected.
| Serious Effects |
["Severe renal impairment (eGFR <30 mL/min/1.73 m^2)","Acute or chronic metabolic acidosis (including diabetic ketoacidosis)","History of serious hypersensitivity reaction to sitagliptin or metformin (e.g., anaphylaxis, angioedema)"]
| Precautions | ["Lactic acidosis risk (see boxed warning)","Pancreatitis (postmarketing cases; discontinue if suspected)","Heart failure (cases with DPP-4 inhibitors; caution in patients with risk factors)","Renal impairment (assess renal function before initiation and periodically)","Hypoglycemia (risk increased when combined with insulin or sulfonylureas)","Vitamin B12 deficiency (monitor with long-term metformin use)"] |
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| Geriatric use |
| Use with caution in patients ≥65 years due to increased risk of metformin-associated lactic acidosis and decreased renal function. Assess renal function before initiation and regularly thereafter. Initiate with 50/500 mg twice daily and titrate slowly. Monitor for adverse effects. |
| Fetal Monitoring | Monitor maternal renal function (creatinine) and glycemic control (HbA1c, glucose). Assess fetal growth via ultrasound every 4-6 weeks in third trimester. Monitor for neonatal hypoglycemia after delivery if metformin used late in pregnancy. |
| Fertility Effects | No adverse effects on fertility reported. Metformin may improve ovulation in women with PCOS. Sitagliptin: No known effect on fertility in animal studies. |