DYNACIRC CR
Clinical safety rating
cautionComprehensive clinical and safety monograph for DYNACIRC CR (DYNACIRC CR).
Dihydropyridine calcium channel blocker that selectively inhibits calcium ion influx across cardiac and vascular smooth muscle cell membranes, leading to vasodilation and reduced peripheral vascular resistance.
| Metabolism | Hepatic via CYP3A4; undergoes extensive first-pass metabolism. |
| Excretion | Primarily hepatic metabolism with biliary excretion; 20% renal, 80% fecal. |
| Half-life | Terminal half-life approximately 7-8 hours; sustained due to controlled-release formulation. |
| Protein binding | >95%, primarily to albumin and alpha-1 acid glycoprotein. |
| Volume of Distribution | 2.8 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral (CR): 20-30% due to first-pass metabolism. |
| Onset of Action | Oral (CR): 2-4 hours for peak plasma concentration. |
| Duration of Action | 24 hours once-daily dosing with sustained antihypertensive effect. |
| Molecular Weight | 371.5 |
Isradipine extended-release (DynaCirc CR) is indicated for hypertension. Initial dose: 5 mg orally once daily. Titrate based on blood pressure response; maximum dose 10 mg once daily.
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | For GFR <30 mL/min, start at 2.5 mg orally once daily; titrate cautiously. No adjustment necessary for GFR >=30 mL/min. |
| Liver impairment | For Child-Pugh Class A or B: start at 2.5 mg orally once daily. For Child-Pugh Class C: avoid use due to lack of data. |
| Pediatric use | Safety and effectiveness in pediatric patients have not been established. |
| Geriatric use | Initial dose: 2.5 mg orally once daily. Titrate slowly due to increased sensitivity and risk of hypotension. |
| 1st trimester | Isradipine crosses the placenta. Limited human data; animal studies show no teratogenicity at therapeutic doses. Consider use if benefit outweighs risk. |
| 2nd trimester | Can cause fetal hypotension and hypoxia. Use only if clearly needed and no safer alternative. |
| 3rd trimester | May cause uterine relaxation and delay labor. Avoid use near term; consider alternative antihypertensives. |
Clinical note
Comprehensive clinical and safety monograph for DYNACIRC CR (DYNACIRC CR).
| Placental transfer | Isradipine crosses the placenta; fetal plasma levels are approximately 50% of maternal levels. |
| Breastfeeding | Isradipine is excreted into breast milk in small amounts (estimated infant dose <1% of maternal weight-adjusted dose). No adverse effects reported in breastfed infants. Use with caution in preterm or low birth weight infants due to potential risk of hypotension. |
| Lactation Rating | L2 (Limited data - probably compatible) |
| Teratogenic Risk | Isradipine (DynaCirc CR) is a pregnancy category C drug. In animal studies, isradipine was not teratogenic in rats or rabbits at doses up to 150 mg/kg/day (approximately 100 times the maximum recommended human dose). However, embryotoxicity and fetotoxicity (increased resorptions, reduced fetal weight, delayed ossification) were observed at high doses. There are no adequate and well-controlled studies in pregnant women. Due to the potential risk of fetal harm, use only if the potential benefit justifies the risk. In the first trimester, avoid use if possible. In second and third trimesters, use with caution; may cause maternal hypotension and reduced uteroplacental perfusion. |
| Fetal Monitoring | Monitor maternal blood pressure regularly, especially after dose changes. Assess for signs of hypotension, dizziness, and reflex tachycardia. In pregnancy, monitor fetal heart rate and growth via ultrasound; watch for signs of uteroplacental insufficiency. In labor and delivery, monitor maternal blood pressure closely to avoid hypotension that could compromise placental perfusion. |
| Fertility Effects | In animal studies, isradipine did not impair fertility in rats at doses up to 100 mg/kg/day. There are no adequate human data on fertility effects. However, calcium channel blockers have been associated with reversible sperm dysfunction in some studies. Clinical significance is unknown. Consider potential effects on male and female fertility when counseling patients. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to isradipine or any dihydropyridine calcium channel blockerSevere aortic stenosisCardiogenic shockUnstable anginaAcute myocardial infarction (within 4 weeks)Second or third degree AV block (unless pacemaker in place)Sick sinus syndrome (unless pacemaker in place)
| Precautions | May cause hypotension, especially in volume-depleted patients, Peripheral edema, Hepatic impairment may require dose adjustment, May increase angina or myocardial infarction in patients with obstructive coronary disease upon initiation or dose escalation |
| Food/Dietary | Grapefruit juice increases isradipine plasma concentrations; avoid concurrent use. High-fat meals may slightly delay absorption but no significant clinical effect. |
| Clinical Pearls | - DYNACIRC CR (isradipine controlled release) is a dihydropyridine calcium channel blocker used for hypertension. - The CR formulation allows once-daily dosing; avoid crushing or chewing tablets. - May cause dose-related peripheral edema, especially in higher doses or in elderly. - Use with caution in patients with aortic stenosis or in those with heart failure due to negative inotropic effects (though less than verapamil). - Grapefruit juice increases bioavailability; consider avoidance or dose adjustment. - Common side effects: headache, dizziness, flushing, and palpitations. |
| Patient Advice | Take exactly as prescribed once daily, preferably in the morning. · Swallow tablet whole; do not crush, chew, or split. · Avoid grapefruit juice while taking this medication. · Do not stop abruptly; may cause rebound hypertension. · Report persistent swelling in ankles/feet, palpitations, or severe dizziness. · May cause dizziness; avoid driving until you know how it affects you. |
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