Isradipine

INDICATIONS AND USAGE Hypertension Isradipine capsules are indicated in the management of hypertension. It may be used alone or concurrently with thiazide-type diuretics.

DOSAGE AND ADMINISTRATION The dosage of isradipine should be individualized. The recommended initial dose of isradipine is 2.5 mg b.i.d. alone or in combination with a thiazide diuretic. An antihypertensive response usually occurs within 2 to 3 hours. Maximal response may require 2 to 4 weeks. If a satisfactory reduction in blood pressure does not occur after this period, the dose may be adjusted in increments of 5 mg/day at 2 to 4 week intervals up to a maximum of 20 mg/day. Most patients, however, show no additional response to doses above 10 mg/day, and adverse effects are increased in frequency above 10 mg/day. The bioavailability of isradipine (increased AUC) is increased in elderly patients (above 65 years of age), patients with hepatic functional impairment, and patients with mild renal impairment. Ordinarily, the starting dose should still be 2.5 mg b.i.d. in these patients.

CONTRAINDICATIONS Isradipine is contraindicated in individuals who have shown hypersensitivity to any of the ingredients in the formulation.

ADVERSE REACTIONS In multiple dose U.S. studies in hypertension, 1228 patients received isradipine alone or in combination with other agents, principally a thiazide diuretic, 934 of them in controlled comparisons with placebo or active agents. An additional 652 patients (which includes 374 normal volunteers) received isradipine in U.S. studies of conditions other than hypertension, and 1321 patients received isradipine in non-U.S. studies. About 500 patients received isradipine in long-term hypertension studies, 410 of them for at least 6 months. The adverse reaction rates given below are principally based on controlled hypertension studies, but rarer serious events are derived from all exposures to isradipine, including foreign marketing experience. Most adverse reactions were mild and related to the vasodilatory effects of isradipine (dizziness, edema, palpitations, flushing, tachycardia), and many were transient. About 5% of isradipine patients left studies prematurely because of adverse reactions (vs. 3% of placebo patients and 6% of active control patients), principally due to headache, edema, dizziness, palpitations, and gastrointestinal disturbances. The following table shows the most common adverse reactions, volunteered or elicited, considered by the investigator to be at least possibly drug related. The results for the isradipine treated patients are presented for all doses pooled together (reported by 1% or greater of patients receiving any dose of isradipine), and also for the two treatment regimens most applicable to the treatment of hypertension with isradipine: (1) initial and maintenance dose of 2.5 mg b.i.d., and (2) initial dose of 2.5 mg b.i.d. followed by maintenance dose of 5 mg b.i.d. Isradipine Adverse Experience All Doses N=934 % 2.5 mg b.i.d. 199 % 5 mg b.i.d.† 150 % 10 mg b.i.d.†† 59 % Placebo % Active Controls* 414 % Headache Dizziness Edema Palpitations 13.7 7.3 7.2 4.0 12.6 8.0 3.5 1.0 10.7 5.3 8.7 4.7 22.0 3.4 8.5 5.1 14.1 4.4 3.0 1.4 9.4 8.2 2.9 1.5 Fatigue Flushing Chest Pain Nausea 3.9 2.6 2.4 1.8 2.5 3.0 2.5 1.0 2.0 2.0 2.7 2.7 8.5 5.1 1.7 5.1 0.3 0.0 2.4 1.7 6.3 1.2 2.9 3.1 Dyspnea Abdominal Discomfort Tachycardia Rash 1.8 1.7 1.5 1.5 0.5 0.0 1.0 1.5 2.7 3.3 1.3 2.0 3.4 1.7 3.4 1.7 1.0 1.7 0.3 0.3 2.2 3.9 0.5 0.7 Pollakiuria Weakness Vomiting Diarrhea 1.5 1.2 1.1 1.1 2.0 0.0 1.0 0.0 1.3 0.7 1.3 2.7 3.4 0.0 0.0 3.4 0.0 0.0 0.3 2.0 <1.0 1.2 0.2 1.9 †Initial dose of 2.5 mg b.i.d. followed by maintenance dose of 5 mg b.i.d. †† Initial dose of 2.5 mg b.i.d. followed by sequential titration to 5 mg b.i.d., 7.5 mg b.i.d., and maintenance dose of 10 mg b.i.d. *Propranolol, prazosin, hydrochlorothiazide, enalapril, captopril. Except for headache, which is not clearly drug-related (see previous table), the more frequent adverse reactions listed show little change, or increase slightly, in frequency over time, as shown in the following table: Incidence Rates for Isradipine (All Doses) by Week (%) Week N 1 694 2 906 3 649 4 847 5 432 6 494 Adverse Reaction Headache Dizziness Edema Palpitations Fatigue Flushing 6.5 1.6 1.2 1.2 0.4 1.2 6.1 1.9 2.5 1.3 1.0 1.3 5.2 1.7 3.2 1.4 1.4 2.0 5.2 2.2 3.2 1.9 1.2 1.4 5.8 2.3 5.3 2.1 1.2 2.1 4.5 2.0 5.5 1.4 1.6 1.4 Week N 7 153 8 377 9 261 10 362 11 107 12 105 Adverse Reaction Headache Dizziness Edema Palpitations Fatigue Flushing 2.0 2.0 5.9 1.3 2.0 3.3 2.7 1.9 5.0 0.8 2.7 1.3 1.9 2.3 4.6 0.8 1.5 1.1 2.8 3.9 4.7 1.7 1.4 0.8 2.8 4.7 3.8 1.9 0.9 0.0 3.8 3.8 3.8 2.9 1.9 0.0 Edema, palpitations, fatigue, and flushing appear to be dose-related, especially at the higher doses of 15 to 20 mg/day. In open-label, long-term studies of up to two years in duration, the adverse events reported were generally the same as those reported in the short-term controlled trials. The overall frequencies of these adverse events were slightly higher in the long-term than in the controlled studies, but as in the controlled trials most adverse reactions were mild and transient. The following …

Drug Interactions Nitroglycerin: Isradipine has been safely coadministered with nitroglycerin. Hydrochlorothiazide: A study in normal healthy volunteers has shown that concomitant administration of isradipine and hydrochlorothiazide does not result in altered pharmacokinetics of either drug. In a study in hypertensive patients, addition of isradipine to existing hydrochlorothiazide therapy did not result in any unexpected adverse effects, and isradipine had an additional antihypertensive effect. Propranolol: In a single dose study in normal volunteers, co-administration of propranolol had a small effect on the rate but no effect on the extent of isradipine bioavailability. Significant increases in AUC (27%) and C max (58%) and decreases in t max (23%) of propranolol were noted in this study. However, concomitant administration of 5 mg b.i.d. isradipine and 40 mg b.i.d. propranolol to healthy volunteers under steady-state conditions had no relevant effect on either drug's bioavailability. AUC and C max differences were <20% between isradipine given singly and in combination with propranolol, and between propranolol given singly and in combination with isradipine. Cimetidine: In a study in healthy volunteers, a one-week course of cimetidine at 400 mg b.i.d. with a single 5 mg dose of isradipine on the sixth day showed an increase in isradipine mean peak plasma concentrations (36%) and significant increase in area under the curve (50%). If isradipine therapy is initiated in a patient currently receiving cimetidine, careful monitoring for adverse reactions is advised and downward dose adjustment may be required. Rifampicin: In a study in healthy volunteers, a six-day course of rifampicin at 600 mg/day followed by a single 5 mg dose of isradipine resulted in a reduction in isradipine levels to below detectable limits. If rifampicin therapy is required, isradipine concentrations and therapeutic effects are likely to be markedly reduced or abolished as a consequence of increased metabolism and higher clearance of isradipine. Warfarin: In a study in healthy volunteers, no clinically relevant pharmacokinetic or pharmacodynamic interaction between isradipine and racemic warfarin was seen when two single oral doses of warfarin (0.7 mg/kg body weight) were administered during 11 days of multiple-dose treatment with 5 mg b.i.d. isradipine. Neither racemic warfarin nor isradipine binding to plasma proteins in vitro was altered by the addition of the other drug. Digoxin: The concomitant administration of isradipine and digoxin in a single-dose pharmacokinetic study did not affect renal, nonrenal and total body clearance of digoxin. Fentanyl Anesthesia: Severe hypotension has been reported during fentanyl anesthesia with concomitant use of a beta blocker and a calcium channel blocker. Even though such interactions have not been seen in clinical studies with isradipine, an increased volume of circulating fluids might be required if such an interaction were to occur.

Mechanism of Action Isradipine is a dihydropyridine calcium channel blocker. It binds to calcium channels with high affinity and specificity and inhibits calcium flux into cardiac and smooth muscle. The effects observed in mechanistic experiments in vitro and studied in intact animals and man are compatible with this mechanism of action and are typical of the class. Except for diuretic activity, the mechanism of which is not clearly understood, the pharmacodynamic effects of isradipine observed in whole animals can also be explained by calcium channel blocking activity, especially dilating effects in arterioles which reduce systemic resistance and lower blood pressure, with a small increase in resting heart rate. Although like other dihydropyridine calcium channel blockers, isradipine has negative inotropic effects in vitro, studies conducted in intact anesthetized animals have shown that the vasodilating effect occurs at doses lower than those which affect contractility. In patients with normal ventricular function, isradipine’s afterload reducing properties lead to some increase in cardiac output. Effects in patients with impaired ventricular function have not been fully studied.

DESCRIPTION Isradipine is a calcium antagonist available for oral administration in capsules containing 2.5 mg or 5 mg. The structural formula of isradipine is: Chemically, isradipine is 3,5-Pyridinedicarboxylic acid, 4-(4-benzofurazanyl)-1,4-dihydro-2,6-dimethyl-,methyl 1-methylethyl ester. Isradipine is a yellow, fine crystalline powder which is odorless or has a faint characteristic odor. Isradipine is practically insoluble in water (<10 mg/L at 37°C), but is soluble in ethanol and freely soluble in acetone, chloroform and methylene chloride. Active Ingredient: isradipine Inactive Ingredients: colloidal silicon dioxide, corn starch, gelatin, lactose monohydrate, microcrystalline cellulose, polyethylene glycol, red iron oxide (5 mg), sodium lauryl sulfate, and titanium dioxide. Black ink contains the following ingredients: Black Iron Oxide, D&C Yellow #10 Aluminum Lake, FD&C Blue #1 Aluminum Lake, FD&C Blue #2 Aluminum Lake, FD&C Red #40 Aluminum Lake, n-Butyl Alcohol, Propylene Glycol, and Shellac Glaze in SD-45 Alcohol. Structural formula of Isradipine

OVERDOSAGE Minimal empirical data are available on isradipine overdosage. Three individual suicide attempts with dosages of isradipine reported to be from 20 mg up to 100 mg resulted in lethargy, sinus tachycardia and, in the case of the person ingesting 100 mg, transient hypotension which responded to fluid therapy. A foreign report of the ingestion of 200 mg of isradipine with ethanol resulted only in flushing, tachycardia with ST depression on ECG, and hypotension, all of which were reversible. The ingestion of 5 mg of isradipine by a 22-month old child and the accidental ingestion of 100 mg of isradipine by a 58-year old female did not result in any sequelae. Available data suggest that, as with other dihydropyridines, overdosage with isradipine might result in excessive peripheral vasodilatation with subsequent marked and probably prolonged systemic hypotension, and tachycardia. Emesis, gastric lavage, administration of activated charcoal followed in 30 minutes by a saline cathartic would be reasonable therapy. Isradipine is highly protein-bound and not removed by hemodialysis. Overdosage characterized by clinically significant hypotension should be treated with active cardiovascular support including monitoring of cardiac and respiratory function, elevation of lower extremities, and attention to circulating fluid volume and urine output. A vasoconstrictor (such as epinephrine, norepinephrine, or levarterenol) may be helpful in restoring a normotensive state, provided that there is no contraindication to its use. Refractory hypotension or AV conduction disturbances may be treated with intravenous calcium salts, or glucagon. Cimetidine should be withheld in such instances due to the risk of further increasing plasma isradipine levels. Significant lethality was observed in mice given oral doses of over 200 mg/kg and rabbits given about 50 mg/kg of isradipine. Rats tolerated doses of over 2000 mg/kg without effects on survival.

HOW SUPPLIED Isradipine Capsules, USP 2.5 mg are Filled Gelatin Capsules Size #3, Cap: White Opaque/Body: White Opaque with Imprint "A-263" on cap and body. Available in bottles of 100's and 500's. Isradipine Capsules, USP 5 mg are Filled Gelatin Capsules Size #3, Cap: Flesh Opaque/Body: Flesh Opaque with Imprint "A-264" on cap and body. Available in bottles of 100's and 500's. Store 20°- 25°C (68°- 77°F) [see USP Controlled Room Temperature]. Dispense contents in a tight, light-resistant container as defined in the USP, with a child-resistant closure as required. Manufactured By: Elite Laboratories, Inc. Northvale, NJ 07647 Rev. 12-2022 IN0548