DYNACIRC
Clinical safety rating
cautionComprehensive clinical and safety monograph for DYNACIRC (DYNACIRC).
Dynacirc (isradipine) is a dihydropyridine calcium channel blocker that inhibits the influx of calcium ions through L-type calcium channels in vascular smooth muscle and cardiac muscle, leading to vasodilation and reduced peripheral vascular resistance, thereby lowering blood pressure.
| Metabolism | Primarily hepatic via CYP3A4 isoenzyme; undergoes extensive first-pass metabolism. |
| Excretion | Primarily hepatic metabolism (CYP3A4) with <1% excreted unchanged in urine; approximately 60% of metabolites are excreted in feces via bile, and 35% in urine. |
| Half-life | Terminal elimination half-life is 7-8 hours. In elderly patients or those with hepatic impairment, half-life may be prolonged up to 14 hours, necessitating dose adjustment. |
| Protein binding | Approximately 95% bound to plasma proteins, primarily albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Volume of distribution is 3-5 L/kg, indicating extensive tissue distribution beyond the vascular compartment. |
| Bioavailability | Oral bioavailability is approximately 30-40% due to extensive first-pass metabolism by CYP3A4 in the liver and gut wall. |
| Onset of Action | Oral administration: onset of antihypertensive effect occurs within 1-2 hours with peak effect at 2-4 hours. |
| Duration of Action | Duration of antihypertensive effect is approximately 24 hours with once-daily dosing, allowing sustained blood pressure control over the dosing interval. |
| Molecular Weight | 371.5 |
2.5-10 mg orally once daily; titrate based on response. Maximum 20 mg/day.
| Dosage form | CAPSULE |
| Renal impairment | CrCl <30 mL/min: 2.5 mg once daily; increase cautiously. CrCl ≥30 mL/min: no adjustment needed. |
| Liver impairment | Child-Pugh A: use with caution, start at 2.5 mg daily. Child-Pugh B or C: not recommended due to extensive hepatic metabolism. |
| Pediatric use | Safety and efficacy not established; no standard pediatric dosing. |
| Geriatric use | Initiate at 2.5 mg once daily; increase slowly due to increased systemic exposure and risk of hypotension. |
| 1st trimester | Isradipine is pregnancy category C. There are no adequate and well-controlled studies in pregnant women. Animal studies have shown embryotoxicity and teratogenicity at high doses. Use only if potential benefit justifies potential risk to fetus. |
| 2nd trimester | Isradipine may cause fetal harm when administered to pregnant women. Use during second trimester only if clearly needed and no alternative therapy is available. |
| 3rd trimester | Isradipine may inhibit labor and cause maternal hypotension and fetal hypoxia. Avoid use during third trimester, especially near term. |
Clinical note
Comprehensive clinical and safety monograph for DYNACIRC (DYNACIRC).
| Placental transfer | Isradipine crosses the placenta. Peak maternal serum concentrations result in similar fetal concentrations. |
| Breastfeeding | Isradipine is excreted into human milk in small amounts. The American Academy of Pediatrics considers isradipine compatible with breastfeeding. However, caution is advised due to potential for cardiovascular effects in the infant. Monitor the infant for hypotension and bradycardia. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | First trimester: No adequate studies; animal reproduction studies not available. Second trimester: Possible fetal bradycardia, hypotension, hypoxia if used after 20 weeks due to calcium channel blocker effects. Third trimester: Increased risk of fetal hypoxia, oligohydramnios, and neonatal complications. Avoid use in pregnancy unless benefit outweighs risk. |
| Fetal Monitoring | Maternal: Blood pressure, heart rate, renal function, electrolytes. Fetal: Heart rate, amniotic fluid volume (for oligohydramnios), growth ultrasound. |
| Fertility Effects | Animal studies show no impairment of fertility; human data limited. Temporary reversible sperm maturation abnormalities reported in some calcium channel blockers. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to isradipine or any component of the formulationSevere aortic stenosisCardiogenic shockUnstable angina
| Precautions | Use with caution in patients with heart failure, aortic stenosis, or severe left ventricular dysfunction., May cause hypotension, especially with concurrent beta-blocker use., Avoid abrupt withdrawal; taper gradually., Monitor for peripheral edema, particularly in the lower extremities. |
| Food/Dietary | Grapefruit juice increases isradipine bioavailability; avoid concurrent use. No other significant food interactions. Maintain consistent salt intake to avoid blood pressure fluctuations. |
| Clinical Pearls | Dynacirc (isradipine) is a dihydropyridine calcium channel blocker used for hypertension. It has high vascular selectivity and minimal negative inotropic effects. Avoid use in patients with advanced aortic stenosis. Dose adjustment may be needed in elderly or hepatic impairment. Can cause gingival hyperplasia; maintain good oral hygiene. |
| Patient Advice | Take exactly as prescribed, usually twice daily. · Do not stop suddenly without consulting your doctor. · May cause dizziness or lightheadedness; avoid driving if affected. · Report any swelling of gums, ankles, or feet. · Avoid grapefruit juice as it can increase drug levels. |
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