REZIPRES
Clinical safety rating: caution
Comprehensive clinical and safety monograph for REZIPRES (REZIPRES).
REZIPRES is a combination of irbesartan, an angiotensin II receptor blocker (ARB), and amlodipine, a calcium channel blocker. Irbesartan inhibits the vasoconstrictor and aldosterone-secreting effects of angiotensin II by selectively blocking the AT1 receptor. Amlodipine inhibits the influx of calcium ions into vascular smooth muscle and cardiac muscle, leading to vasodilation and reduced peripheral vascular resistance.
| Metabolism | Irbesartan is metabolized via glucuronidation and oxidation by CYP2C9. Amlodipine is extensively metabolized in the liver via CYP3A4. |
| Excretion | Primarily hepatic metabolism via CYP3A4 and CYP2C9, with 60% eliminated in feces and 25% in urine as metabolites; <5% excreted unchanged in urine. |
| Half-life | Terminal elimination half-life is approximately 40-50 hours, supporting once-daily dosing; steady-state achieved in 7-10 days. |
| Protein binding | >99% bound, primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 30-50 L (0.43-0.71 L/kg for a 70 kg adult), indicating extensive extravascular distribution. |
| Bioavailability | Oral bioavailability 50-60% due to first-pass metabolism; food decreases absorption by 20%. |
| Onset of Action | Oral: 2-4 hours after first dose for detectable blood pressure reduction; maximal effect in 2-4 weeks. |
| Duration of Action | 24 hours with once-daily dosing; blood pressure reduction sustained over 24 hours without loss at trough. |
Adults: 2 mg orally twice daily.
| Dosage form | SOLUTION |
| Renal impairment | GFR ≥30 mL/min: No adjustment. GFR <30 mL/min: 1 mg orally twice daily. ESRD (dialysis): 1 mg orally once daily. |
| Liver impairment | Child-Pugh A: No adjustment. Child-Pugh B: 1 mg orally twice daily. Child-Pugh C: 0.5 mg orally twice daily. |
| Pediatric use | Children <12 years: Not established. Children ≥12 years: Same as adult dosing. |
| Geriatric use | No specific dose adjustment; monitor renal function and use lowest effective dose. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for REZIPRES (REZIPRES).
| Breastfeeding | Contraindicated during breastfeeding. M/P ratio unknown; drug is excreted in animal milk. Risk of infant exposure and potential adverse effects similar to those in adults. |
| Teratogenic Risk | Pregnancy Category X. First trimester: high risk of major congenital malformations including craniofacial, cardiac, and neural tube defects based on animal studies and human case reports. Second and third trimesters: fetal growth restriction, oligohydramnios, and neonatal renal failure. Contraindicated in pregnancy. |
■ FDA Black Box Warning
WARNING: FETAL TOXICITY. Drugs acting directly on the renin-angiotensin system can cause injury and death to the developing fetus. Discontinue as soon as possible once pregnancy is detected.
| Serious Effects |
["Pregnancy (Category D)","Hypersensitivity to irbesartan, amlodipine, or any component of the formulation","Concomitant use with aliskiren in patients with diabetes"]
| Precautions | ["Hypotension in volume- or salt-depleted patients","Increased angina or myocardial infarction with calcium channel blockers, especially in patients with severe obstructive coronary artery disease","Monitor renal function and potassium levels","Avoid use in patients with severe renal impairment (GFR <30 mL/min)"] |
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| Fetal Monitoring |
| Pregnancy test before initiation and monthly thereafter; fetal ultrasound for anomalies and amniotic fluid volume assessment; maternal renal and hepatic function tests every 4 weeks; consult maternal-fetal medicine specialist if pregnancy occurs. |
| Fertility Effects | May impair female fertility due to hormonal disruption observed in animal studies. Reversible upon discontinuation. Male fertility effects include reduced spermatogenesis and sperm motility. |