Isradipine

Pronunciation

(iz RA di peen)

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Capsule, Oral:

Generic: 2.5 mg, 5 mg

Pharmacologic Category

• Antihypertensive
• Calcium Channel Blocker
• Calcium Channel Blocker, Dihydropyridine

Pharmacology

Inhibits calcium ion from entering the “slow channels” or select voltage-sensitive areas of vascular smooth muscle and myocardium during depolarization, producing relaxation of vascular smooth muscle, resulting in coronary vasodilation and reduced blood pressure; increases myocardial oxygen delivery in patients with vasospastic angina

Absorption

90% to 95%, but large first-pass effect

Distribution

V_d: 3 L/kg

Metabolism

Extensive first-pass effect; hepatically metabolized via cytochrome P450 isoenzyme CYP3A4; major metabolic pathways include oxidation and ester cleavage; six inactive metabolites have been identified

Excretion

Urine (60% to 65% as metabolites); feces (25% to 30%)

Onset of Action

2-3 hours; Note: Full hypotensive effect may not occur for 2-4 weeks

Time to Peak

Serum: 1-1.5 hours

Duration of Action

>12 hours

Half-Life Elimination

Alpha half-life: 1.5-2 hours; Terminal half-life: 8 hours

Protein Binding

95%

Special Populations: Hepatic Function Impairment

The C_max increases by 32%

Special Populations: Elderly

The AUC and C_max increases.

Use: Labeled Indications

Hypertension: Management of hypertension (may be used alone or concurrently with thiazide-type diuretics).

The 2014 guideline for the management of high blood pressure in adults (JNC 8) recommends initiation of pharmacologic treatment to lower blood pressure for the following patients (JNC8 [James, 2013]):

• Patients ≥60 years of age, with systolic blood pressure (SBP) ≥150 mm Hg or diastolic blood pressure (DBP) ≥90 mm Hg. Goal of therapy is SBP <150 mm Hg and DBP <90 mm Hg.

• Patients <60 years of age, with SBP ≥140 mm Hg or DBP ≥90 mm Hg. Goal of therapy is SBP <140 mm Hg and DBP <90 mm Hg.

• Patients ≥18 years of age with diabetes, with SBP ≥140 mm Hg or DBP ≥90 mm Hg. Goal of therapy is SBP <140 mm Hg and DBP <90 mm Hg.

• Patients ≥18 years of age with chronic kidney disease (CKD), with SBP ≥140 mm Hg or DBP ≥90 mm Hg. Goal of therapy is SBP <140 mm Hg and DBP <90 mm Hg.

In patients with chronic kidney disease (CKD), regardless of race or diabetes status, the use of an ACE inhibitor (ACEI) or angiotensin receptor blocker (ARB) as initial therapy is recommended to improve kidney outcomes. In the general nonblack population (without CKD) including those with diabetes, initial antihypertensive treatment should consist of a thiazide-type diuretic, calcium channel blocker, ACEI, or ARB. In the general black population (without CKD) including those with diabetes, initial antihypertensive treatment should consist of a thiazide-type diuretic or a calcium channel blocker instead of an ACEI or ARB.

Use: Unlabeled

Pediatric hypertension

Contraindications

Hypersensitivity to isradipine or any component of the formulation

Dosing: Adult

Hypertension: Oral: 2.5 mg twice daily; antihypertensive response occurs in 2-3 hours; maximal response in 2-4 weeks; increase dose at 2- to 4-week intervals at 2.5-5 mg increments; usual dose range (ASH/ISH [Weber, 2014]): 5-10 mg twice daily. Note: Most patients show no improvement with doses >10 mg daily except adverse reaction rate increases; therefore, maximal dose in older adults should be 10 mg daily.

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Hypertension (off-label use): Oral: Initial: 0.15-0.2 mg/kg/day in 3-4 divided doses; maximum 0.8 mg/kg/day, up to 20 mg daily (NHBPEP, 2004).

Dosing: Renal Impairment

There are no dosage adjustments provided in manufacturer's labeling; however, bioavailability is increased with mild renal impairment and decreased with severe renal impairment. Other sources recommend that no initial dosage adjustment is required (Aronoff, 2007). Isradipine is not removed by hemodialysis; therefore, supplemental doses after hemodialysis are not necessary (Schonholzer, 1992).

Dosing: Hepatic Impairment

There are no dosage adjustments provided in manufacturer's labeling; however, peak serum concentrations are increased by 32% and bioavailability is increased by 52%.

Extemporaneously Prepared

A 1 mg/mL oral suspension may be made from isradipine capsules; glycerin, USP; and Simple Syrup, N.F. Empty the contents of ten 5 mg isradipine capsules into a glass mortar. Add a small portion of glycerin, USP and mix to a fine paste; mix while adding 15 mL of simple syrup and transfer contents to a 60 mL amber glass prescription bottle. Rinse mortar with 10 mL simple syrup, NF and transfer to the prescription bottle; repeat, and add quantity of vehicle sufficient to make 50 mL. Label "protect from light", "refrigerate", and "shake well". Stable for 35 days when stored in amber glass prescription bottles in the dark and refrigerated.

MacDonald JL, Johnson CE, and Jacobson P, “Stability of Isradipine in Extemporaneously Compounded Oral Liquids,” Am J Hosp Pharm, 1994, 51(19):2409-11.7847406

Administration

May be administered without regard to meals.

Dietary Considerations

May be taken without regard to meals.

Storage

Store at 20°C to 25°C (68°F to 77°F) in a tight container, protected from moisture, humidity, and light.

Drug Interactions

Alfuzosin: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Alpha1-Blockers: May enhance the hypotensive effect of Calcium Channel Blockers. Monitor therapy

Amifostine: Blood Pressure Lowering Agents may enhance the hypotensive effect of Amifostine. Management: When amifostine is used at chemotherapy doses, blood pressure lowering medications should be withheld for 24 hours prior to amifostine administration. If blood pressure lowering therapy cannot be withheld, amifostine should not be administered. Consider therapy modification

Amphetamines: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Antifungal Agents (Azole Derivatives, Systemic): May enhance the adverse/toxic effect of Calcium Channel Blockers. Specifically, itraconazole may enhance the negative inotropic effects of verapamil or diltiazem. Antifungal Agents (Azole Derivatives, Systemic) may decrease the metabolism of Calcium Channel Blockers. Fluconazole and isavuconazonium likely exert weaker effects than other azoles and are addressed in separate monographs. Management: Concurrent use of felodipine or nisoldipine with itraconazole is specifically contraindicated. Frequent monitoring is warranted with any such combination; calcium channel blocker dose reductions may be required. Exceptions: Fluconazole; Isavuconazonium Sulfate. Consider therapy modification

Antipsychotic Agents (Second Generation [Atypical]): Blood Pressure Lowering Agents may enhance the hypotensive effect of Antipsychotic Agents (Second Generation [Atypical]). Monitor therapy

Aprepitant: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Atosiban: Calcium Channel Blockers may enhance the adverse/toxic effect of Atosiban. Specifically, there may be an increased risk for pulmonary edema and/or dyspnea. Monitor therapy

Barbiturates: May increase the metabolism of Calcium Channel Blockers. Management: Monitor for decreased therapeutic effects of calcium channel blockers with concomitant barbiturate therapy. Calcium channel blocker dose adjustments may be necessary. Nimodipine Canadian labeling contraindicates concomitant use with phenobarbital. Monitor therapy

Barbiturates: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Bosentan: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

Brimonidine (Topical): May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Calcium Channel Blockers (Nondihydropyridine): Calcium Channel Blockers (Dihydropyridine) may enhance the hypotensive effect of Calcium Channel Blockers (Nondihydropyridine). Calcium Channel Blockers (Nondihydropyridine) may increase the serum concentration of Calcium Channel Blockers (Dihydropyridine). Monitor therapy

Calcium Salts: May diminish the therapeutic effect of Calcium Channel Blockers. Monitor therapy

CarBAMazepine: May increase the metabolism of Calcium Channel Blockers (Dihydropyridine). Management: Consider calcium channel blocker (CCB) dose adjustments or alternative therapy in patients receiving concomitant carbamazepine. Nimodipine Canadian labeling contraindicates concurrent use with carbamazepine. Consider therapy modification

Cimetidine: May increase the serum concentration of Calcium Channel Blockers. Management: Consider alternatives to cimetidine. If no suitable alternative exists, monitor for increased effects of calcium channel blockers following cimetidine initiation/dose increase, and decreased effects following cimetidine discontinuation/dose decrease. Consider therapy modification

Clopidogrel: Calcium Channel Blockers may diminish the therapeutic effect of Clopidogrel. Monitor therapy

Conivaptan: May increase the serum concentration of CYP3A4 Substrates. Avoid combination

CycloSPORINE (Systemic): Calcium Channel Blockers (Dihydropyridine) may increase the serum concentration of CycloSPORINE (Systemic). CycloSPORINE (Systemic) may increase the serum concentration of Calcium Channel Blockers (Dihydropyridine). Monitor therapy

CYP3A4 Inducers (Moderate): May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

CYP3A4 Inducers (Strong): May increase the metabolism of CYP3A4 Substrates. Management: Consider an alternative for one of the interacting drugs. Some combinations may be specifically contraindicated. Consult appropriate manufacturer labeling. Consider therapy modification

CYP3A4 Inhibitors (Moderate): May decrease the metabolism of CYP3A4 Substrates. Monitor therapy

CYP3A4 Inhibitors (Strong): May decrease the metabolism of CYP3A4 Substrates. Consider therapy modification

Dabrafenib: May decrease the serum concentration of CYP3A4 Substrates. Management: Seek alternatives to the CYP3A4 substrate when possible. If concomitant therapy cannot be avoided, monitor clinical effects of the substrate closely (particularly therapeutic effects). Consider therapy modification

Dapoxetine: May enhance the orthostatic hypotensive effect of Calcium Channel Blockers. Monitor therapy

Dasatinib: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Deferasirox: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

Diazoxide: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

DULoxetine: Blood Pressure Lowering Agents may enhance the hypotensive effect of DULoxetine. Monitor therapy

Efavirenz: May decrease the serum concentration of Calcium Channel Blockers. Monitor therapy

Enzalutamide: May decrease the serum concentration of CYP3A4 Substrates. Management: Concurrent use of enzalutamide with CYP3A4 substrates that have a narrow therapeutic index should be avoided. Use of enzalutamide and any other CYP3A4 substrate should be performed with caution and close monitoring. Consider therapy modification

Fluconazole: May increase the serum concentration of Calcium Channel Blockers. Monitor therapy

Fosaprepitant: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Fosphenytoin: Calcium Channel Blockers may increase the serum concentration of Fosphenytoin. Management: Monitor for phenytoin toxicity with concomitant use of a calcium channel blocker (CCB) or decreased phenytoin effects with CCB discontinuation. Monitor for decreased CCB therapeutic effects. Nimodipine Canadian labeling contraindicates use with phenytoin. Consider therapy modification

Fusidic Acid (Systemic): May increase the serum concentration of CYP3A4 Substrates. Avoid combination

Herbs (Hypertensive Properties): May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Herbs (Hypotensive Properties): May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Highest Risk QTc-Prolonging Agents: QTc-Prolonging Agents (Indeterminate Risk and Risk Modifying) may enhance the QTc-prolonging effect of Highest Risk QTc-Prolonging Agents. Management: Avoid such combinations when possible. Use should be accompanied by close monitoring for evidence of QT prolongation or other alterations of cardiac rhythm. Consider therapy modification

Hypotension-Associated Agents: Blood Pressure Lowering Agents may enhance the hypotensive effect of Hypotension-Associated Agents. Monitor therapy

Idelalisib: May increase the serum concentration of CYP3A4 Substrates. Avoid combination

Ivacaftor: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Levodopa: Blood Pressure Lowering Agents may enhance the hypotensive effect of Levodopa. Monitor therapy

Luliconazole: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Macrolide Antibiotics: May decrease the metabolism of Calcium Channel Blockers. Management: Consider using a noninteracting macrolide. Felodipine Canadian labeling specifically recommends avoiding its use in combination with clarithromycin. Exceptions: Azithromycin (Systemic); Fidaxomicin; Roxithromycin; Spiramycin. Consider therapy modification

Magnesium Salts: Calcium Channel Blockers may enhance the adverse/toxic effect of Magnesium Salts. Magnesium Salts may enhance the hypotensive effect of Calcium Channel Blockers. Monitor therapy

Melatonin: May diminish the antihypertensive effect of Calcium Channel Blockers (Dihydropyridine). Monitor therapy

Methylphenidate: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

MiFEPRIStone: May increase the serum concentration of CYP3A4 Substrates. Management: Minimize doses of CYP3A4 substrates, and monitor for increased concentrations/toxicity, during and 2 weeks following treatment with mifepristone. Avoid cyclosporine, dihydroergotamine, ergotamine, fentanyl, pimozide, quinidine, sirolimus, and tacrolimus. Consider therapy modification

MiFEPRIStone: May enhance the QTc-prolonging effect of QTc-Prolonging Agents (Indeterminate Risk and Risk Modifying). Management: Though the drugs listed here have uncertain QT-prolonging effects, they all have some possible association with QT prolongation and should generally be avoided when possible. Consider therapy modification

Mitotane: May decrease the serum concentration of CYP3A4 Substrates. Management: Doses of CYP3A4 substrates may need to be adjusted substantially when used in patients being treated with mitotane. Consider therapy modification

Moderate Risk QTc-Prolonging Agents: QTc-Prolonging Agents (Indeterminate Risk and Risk Modifying) may enhance the QTc-prolonging effect of Moderate Risk QTc-Prolonging Agents. Monitor therapy

Molsidomine: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Nafcillin: May increase the metabolism of Calcium Channel Blockers. Consider therapy modification

Naftopidil: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Netupitant: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Neuromuscular-Blocking Agents (Nondepolarizing): Calcium Channel Blockers may enhance the neuromuscular-blocking effect of Neuromuscular-Blocking Agents (Nondepolarizing). Monitor therapy

Nicergoline: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Nicorandil: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Nitroprusside: Blood Pressure Lowering Agents may enhance the hypotensive effect of Nitroprusside. Monitor therapy

Obinutuzumab: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Management: Consider temporarily withholding blood pressure lowering medications beginning 12 hours prior to obinutuzumab infusion and continuing until 1 hour after the end of the infusion. Consider therapy modification

Palbociclib: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

Pentoxifylline: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Phenytoin: Calcium Channel Blockers may increase the serum concentration of Phenytoin. Phenytoin may decrease the serum concentration of Calcium Channel Blockers. Management: Avoid use of nimodipine or nifedipine with phenytoin. Monitor for phenytoin toxicity and/or decreased calcium channel blocker effects with any concurrent use. Consider therapy modification

Phosphodiesterase 5 Inhibitors: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Prostacyclin Analogues: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Quinagolide: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Rifamycin Derivatives: May decrease the serum concentration of Calcium Channel Blockers. This primarily affects oral forms of calcium channel blockers. Management: The labeling for some US and Canadian calcium channel blockers contraindicate use with rifampin, however recommendations vary. Consult appropriate labeling. Consider therapy modification

Siltuximab: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

Simeprevir: May increase the serum concentration of CYP3A4 Substrates. Monitor therapy

St John's Wort: May decrease the serum concentration of CYP3A4 Substrates. Management: Consider an alternative for one of the interacting drugs. Some combinations may be specifically contraindicated. Consult appropriate manufacturer labeling. Consider therapy modification

Stiripentol: May increase the serum concentration of CYP3A4 Substrates. Management: Use of stiripentol with CYP3A4 substrates that are considered to have a narrow therapeutic index should be avoided due to the increased risk for adverse effects and toxicity. Any CYP3A4 substrate used with stiripentol requires closer monitoring. Consider therapy modification

Tacrolimus (Systemic): Calcium Channel Blockers (Dihydropyridine) may increase the serum concentration of Tacrolimus (Systemic). Monitor therapy

Tocilizumab: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

Yohimbine: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Adverse Reactions

>10%: Central nervous system: Headache (dose related 2% to 22%)

1% to 10%:

Cardiovascular: Edema (dose related 1% to 9%), flushing (dose related 1% to 5%), palpitations (dose related 1% to 5%), chest pain (3%), tachycardia (1% to 3%)

Central nervous system: Fatigue (dose related ≤9%), dizziness (2% to 8%)

Dermatologic: Skin rash (2%)

Gastrointestinal: Nausea (3% to 5%), abdominal distress (≤3%), diarrhea (≤3%), vomiting (≤1%)

Neuromuscular & skeletal: Weakness (≤1%)

Renal: Urinary frequency (1% to 3%)

Respiratory: Dyspnea (3%)

<1% (Limited to important or life-threatening): Atrial fibrillation, cardiac failure, cerebrovascular accident, cough, decreased libido, depression, foot cramps, hyperhidrosis, hypotension, impotence, increased liver enzymes, insomnia, leg cramps, leukopenia, myocardial infarction, nocturia, numbness, paresthesia, pruritus, sore throat, syncope, transient ischemic attacks, urticaria, ventricular fibrillation, visual disturbance

Warnings/Precautions

Concerns related to adverse effects:

• Angina/MI: Increased angina and/or MI has occurred with initiation or dosage titration of dihydropyridine calcium channel blockers. Reflex tachycardia may occur resulting in angina and/or MI in patients with obstructive coronary disease, especially in the absence of concurrent beta-blockade.

• Hypotension/syncope: Symptomatic hypotension with or without syncope can rarely occur; blood pressure must be lowered at a rate appropriate for the patient's clinical condition.

• Peripheral edema: A common side effect is peripheral edema (dose-dependent); may begin within 2-3 weeks of starting therapy.

Disease-related concerns:

• Aortic stenosis: Use with extreme caution in patients with severe aortic stenosis; may reduce coronary perfusion resulting in ischemia.

• Heart failure (HF): The ACCF/AHA heart failure guidelines recommend to avoid use in patients with heart failure due to lack of benefit and/or worse outcomes with calcium channel blockers in general (ACCF/AHA [Yancy, 2013]).

• Hepatic impairment: Use with caution in patients with hepatic impairment; may require lower starting dose.

• Hypertrophic cardiomyopathy (HCM) with outflow tract obstruction: Use with caution in patients with HCM and outflow tract obstruction since reduction in afterload may worsen symptoms associated with this condition.

Monitoring Parameters

Blood pressure, heart rate

Pregnancy Risk Factor

C

Pregnancy Considerations

Adverse events were not observed in animal reproduction studies when using doses that were not maternally toxic. Isradipine crosses the human placenta (Lunell, 1993). Untreated chronic maternal hypertension is associated with adverse events in the fetus, infant, and mother. If treatment for hypertension during pregnancy is needed, other agents are preferred (ACOG, 2013).

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience loss of strength and energy or headache. Have patient report immediately to prescriber arrhythmia, severe dizziness, passing out, or swelling of arms or legs (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.