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Calan®
verapamil hydrochloride tablets
DESCRIPTION
Calan (verapamil HCl) is a calcium ion influx inhibitor (slow-channel blocker or calcium ion antagonist) available for oral administration in film-coated tablets containing 40 mg, 80 mg, or 120 mg of verapamil hydrochloride.
The structural formula of verapamil HCl is
Benzeneacetonitrile, α-[3-[[2-(3,4-dimethoxyphenyl)ethyl] methylamino]propyl]-3,4-dimethoxy-α-(1-methylethyl) hydrochloride
Verapamil HCl is an almost white, crystalline powder, practically free of odor, with a bitter taste. It is soluble in water, chloroform, and methanol. Verapamil HCl is not chemically related to other cardioactive drugs.
Inactive ingredients include microcrystalline cellulose, corn starch, gelatin, hydroxypropyl cellulose, hypromellose, iron oxide colorant, lactose, magnesium stearate, polyethylene glycol, talc, and titanium dioxide.
CLINICAL PHARMACOLOGY
Calan is a calcium ion influx inhibitor (slow-channel blocker or calcium ion antagonist) that exerts its pharmacologic effects by modulating the influx of ionic calcium across the cell membrane of the arterial smooth muscle as well as in conductile and contractile myocardial cells.
Mechanism of action
Pharmacokinetics and metabolism
More than 90% of the orally administered dose of Calan is absorbed. Because of rapid biotransformation of verapamil during its first pass through the portal circulation, bioavailability ranges from 20% to 35%. Peak plasma concentrations are reached between 1 and 2 hours after oral administration. Chronic oral administration of 120 mg of verapamil HCl every 6 hours resulted in plasma levels of verapamil ranging from 125 to 400 ng/ml, with higher values reported occasionally. A nonlinear correlation between the verapamil dose administered and verapamil plasma levels does exist. No relationship has been established between the plasma concentration of verapamil and a reduction in blood pressure. In early dose titration with verapamil a relationship exists between verapamil plasma concentration and prolongation of the PR interval. However, during chronic administration this relationship may disappear. The mean elimination half-life in single-dose studies ranged from 2.8 to 7.4 hours. In these same studies, after repetitive dosing, the half-life increased to a range from 4.5 to 12.0 hours (after less than 10 consecutive doses given 6 hours apart). Half-life of verapamil may increase during titration. Aging may affect the pharmacokinetics of verapamil. Elimination half-life may be prolonged in the elderly. In healthy men, orally administered Calan undergoes extensive metabolism in the liver. Twelve metabolites have been identified in plasma; all except norverapamil are present in trace amounts only. Norverapamil can reach steady-state plasma concentrations approximately equal to those of verapamil itself. The cardiovascular activity of norverapamil appears to be approximately 20% that of verapamil. Approximately 70% of an administered dose is excreted as metabolites in the urine and 16% or more in the feces within 5 days. About 3% to 4% is excreted in the urine as unchanged drug. Approximately 90% is bound to plasma proteins. In patients with hepatic insufficiency, metabolism is delayed and elimination half-life prolonged up to 14 to 16 hours (see Precautions); the volume of distribution is increased and plasma clearance reduced to about 30% of normal. Verapamil clearance values suggest that patients with liver dysfunction may attain therapeutic verapamil plasma concentrations with one third of the oral daily dose required for patients with normal liver function.
After four weeks of oral dosing (120 mg q.i.d.), verapamil and norverapamil levels were noted in the cerebrospinal fluid with estimated partition coefficient of 0.06 for verapamil and 0.04 for norverapamil.
Hemodynamics and myocardial metabolism
Calan reduces afterload and myocardial contractility. Improved left ventricular diastolic function in patients with IHSS and those with coronary heart disease has also been observed with Calan therapy. In most patients, including those with organic cardiac disease, the negative inotropic action of Calan is countered by reduction of afterload, and cardiac index is usually not reduced. However in patients with severe left ventricular dysfunction (eg, pulmonary wedge pressure above 20 mm Hg or ejection fraction less than 30%), or in patients taking beta-adrenergic blocking agents or other cardiodepressant drugs, deterioration of ventricular function may occur (see Drug interactions).
Pulmonary function
Calan does not induce bronchoconstriction and, hence, does not impair ventilatory function.
INDICATIONS AND USAGE
Calan tablets are indicated for the treatment of the following:
Angina
- Angina at rest including:
— Vasospastic (Prinzmetal's variant) angina— Unstable (crescendo, pre-infarction) angina
- Chronic stable angina (classic effort-associated angina)
Arrhythmias
- In association with digitalis for the control of ventricular rate at rest and during stress in patients with chronic atrial flutter and/or atrial fibrillation (see Warnings: Accessory bypass tract)
- Prophylaxis of repetitive paroxysmal supraventricular tachycardia
Essential hypertension
CONTRAINDICATIONS
Verapamil HCl tablets are contraindicated in:
- Severe left ventricular dysfunction (see Warnings)
- Hypotension (systolic pressure less than 90 mm Hg) or cardiogenic shock
- Sick sinus syndrome (except in patients with a functioning artificial ventricular pacemaker)
- Second- or third-degree AV block (except in patients with a functioning artificial ventricular pacemaker)
- Patients with atrial flutter or atrial fibrillation and an accessory bypass tract (eg, Wolff-Parkinson-White, Lown-Ganong-Levine syndromes). (See Warnings.)
- Patients with known hypersensitivity to verapamil hydrochloride.
WARNINGS
Heart failure
Verapamil has a negative inotropic effect, which in most patients is compensated by its afterload reduction (decreased systemic vascular resistance) properties without a net impairment of ventricular performance. In clinical experience with 4,954 patients, 87 (1.8%) developed congestive heart failure or pulmonary edema. Verapamil should be avoided in patients with severe left ventricular dysfunction (eg, ejection fraction less than 30%) or moderate to severe symptoms of cardiac failure and in patients with any degree of ventricular dysfunction if they are receiving a beta-adrenergic blocker (see Drug interactions). Patients with milder ventricular dysfunction should, if possible, be controlled with optimum doses of digitalis and/or diuretics before verapamil treatment. (Note interactions with digoxin under Precautions.)
Hypotension
Occasionally, the pharmacologic action of verapamil may produce a decrease in blood pressure below normal levels, which may result in dizziness or symptomatic hypotension. The incidence of hypotension observed in 4,954 patients enrolled in clinical trials was 2.5%. In hypertensive patients, decreases in blood pressure below normal are unusual. Tilt-table testing (60 degrees) was not able to induce orthostatic hypotension.
Elevated liver enzymes
Elevations of transaminases with and without concomitant elevations in alkaline phosphatase and bilirubin have been reported. Such elevations have sometimes been transient and may disappear even with continued verapamil treatment. Several cases of hepatocellular injury related to verapamil have been proven by rechallenge; half of these had clinical symptoms (malaise, fever, and/or right upper quadrant pain), in addition to elevation of SGOT, SGPT, and alkaline phosphatase. Periodic monitoring of liver function in patients receiving verapamil is therefore prudent.
Accessory bypass tract (Wolff-Parkinson-White or Lown-Ganong-Levine)
Some patients with paroxysmal and/or chronic atrial fibrillation or atrial flutter and a coexisting accessory AV pathway have developed increased antegrade conduction across the accessory pathway bypassing the AV node, producing a very rapid ventricular response or ventricular fibrillation after receiving intravenous verapamil (or digitalis). Although a risk of this occurring with oral verapamil has not been established, such patients receiving oral verapamil may be at risk and its use in these patients is contraindicated (see Contraindications). Treatment is usually DC-cardioversion. Cardioversion has been used safely and effectively after oral Calan.
Atrioventricular block
The effect of verapamil on AV conduction and the SA node may cause asymptomatic first-degree AV block and transient bradycardia, sometimes accompanied by nodal escape rhythms. PR-interval prolongation is correlated with verapamil plasma concentrations especially during the early titration phase of therapy. Higher degrees of AV block, however, were infrequently (0.8%) observed. Marked first-degree block or progressive development to second- or third-degree AV block requires a reduction in dosage or, in rare instances, discontinuation of verapamil HCl and institution of appropriate therapy, depending on the clinical situation.
Patients with hypertrophic cardiomyopathy (IHSS)
In 120 patients with hypertrophic cardiomyopathy (most of them refractory or intolerant to propranolol) who received therapy with verapamil at doses up to 720 mg/day, a variety of serious adverse effects were seen. Three patients died in pulmonary edema; all had severe left ventricular outflow obstruction and a past history of left ventricular dysfunction. Eight other patients had pulmonary edema and/or severe hypotension; abnormally high (greater than 20 mm Hg) pulmonary wedge pressure and a marked left ventricular outflow obstruction were present in most of these patients. Concomitant administration of quinidine (see Drug interactions) preceded the severe hypotension in 3 of the 8 patients (2 of whom developed pulmonary edema). Sinus bradycardia occurred in 11% of the patients, second-degree AV block in 4%, and sinus arrest in 2%. It must be appreciated that this group of patients had a serious disease with a high mortality rate. Most adverse effects responded well to dose reduction, and only rarely did verapamil use have to be discontinued.
PRECAUTIONS
General
Drug interactions
Antiarrhythmic agents
Other
Carcinogenesis, mutagenesis, impairment of fertility
An 18-month toxicity study in rats, at a low multiple (6-fold) of the maximum recommended human dose, and not the maximum tolerated dose, did not suggest a tumorigenic potential. There was no evidence of a carcinogenic potential of verapamil administered in the diet of rats for two years at doses of 10, 35, and 120 mg/kg/day or approximately 1, 3.5, and 12 times, respectively, the maximum recommended human daily dose (480 mg/day or 9.6 mg/kg/day).
Verapamil was not mutagenic in the Ames test in 5 test strains at 3 mg per plate with or without metabolic activation.
Studies in female rats at daily dietary doses up to 5.5 times (55 mg/kg/day) the maximum recommended human dose did not show impaired fertility. Effects on male fertility have not been determined.
Pregnancy
Labor and delivery
It is not known whether the use of verapamil during labor or delivery has immediate or delayed adverse effects on the fetus, or whether it prolongs the duration of labor or increases the need for forceps delivery or other obstetric intervention. Such adverse experiences have not been reported in the literature, despite a long history of use of verapamil in Europe in the treatment of cardiac side effects of beta-adrenergic agonist agents used to treat premature labor.
Nursing mothers
Verapamil is excreted in human milk. Because of the potential for adverse reactions in nursing infants from verapamil, nursing should be discontinued while verapamil is administered.
Pediatric use
Safety and effectiveness in pediatric patients have not been established.
Animal pharmacology and/or animal toxicology
In chronic animal toxicology studies verapamil caused lenticular and/or suture line changes at 30 mg/kg/day or greater, and frank cataracts at 62.5 mg/kg/day or greater in the beagle dog but not in the rat. Development of cataracts due to verapamil has not been reported in man.
ADVERSE REACTIONS
Serious adverse reactions are uncommon when Calan therapy is initiated with upward dose titration within the recommended single and total daily dose. See Warnings for discussion of heart failure, hypotension, elevated liver enzymes, AV block, and rapid ventricular response. Reversible (upon discontinuation of verapamil) non-obstructive, paralytic ileus has been infrequently reported in association with the use of verapamil. The following reactions to orally administered verapamil occurred at rates greater than 1.0% or occurred at lower rates but appeared clearly drug-related in clinical trials in 4,954 patients:
| Constipation | 7.3% | Dyspnea | 1.4% |
| Dizziness | 3.3% | Bradycardia (HR <50/min) | 1.4% |
| Nausea | 2.7% | AV block total (1°, 2°, 3°) | 1.2% |
| Hypotension | 2.5% | 2° and 3° | 0.8% |
| Headache | 2.2% | Rash | 1.2% |
| Edema | 1.9% | Flushing | 0.6% |
| CHF, Pulmonary edema | 1.8% | ||
| Fatigue | 1.7% | ||
| Elevated liver enzymes (see Warnings) | |||
In clinical trials related to the control of ventricular response in digitalized patients who had atrial fibrillation or flutter, ventricular rates below 50 at rest occurred in 15% of patients and asymptomatic hypotension occurred in 5% of patients.
The following reactions, reported in 1.0% or less of patients, occurred under conditions (open trials, marketing experience) where a causal relationship is uncertain; they are uled to alert the physician to a possible relationship:
Cardiovascular: angina pectoris, atrioventricular dissociation, chest pain, claudication, myocardial infarction, palpitations, purpura (vasculitis), syncope.
Digestive system: diarrhea, dry mouth, gastrointestinal distress, gingival hyperplasia.
Hemic and lymphatic: ecchymosis or bruising.
Nervous system: cerebrovascular accident, confusion, equilibrium disorders, insomnia, muscle cramps, paresthesia, psychotic symptoms, shakiness, somnolence.
Skin: arthralgia and rash, exanthema, hair loss, hyperkeratosis, macules, sweating, urticaria, Stevens-Johnson syndrome, erythema multiforme.
Special senses: blurred vision, tinnitus.
Urogenital: gynecomastia, galactorrhea/hyperprolactinemia, increased urination, spotty menstruation, impotence.
Treatment of acute cardiovascular adverse reactions
The frequency of cardiovascular adverse reactions that require therapy is rare; hence, experience with their treatment is limited. Whenever severe hypotension or complete AV block occurs following oral administration of verapamil, the appropriate emergency measures should be applied immediately; eg, intravenously administered norepinephrine bitartrate, atropine sulfate, isoproterenol HCl (all in the usual doses), or calcium gluconate (10% solution). In patients with hypertrophic cardiomyopathy (IHSS), alpha-adrenergic agents (phenylephrine HCl, metaraminol bitartrate, or methoxamine HCl) should be used to maintain blood pressure, and isoproterenol and norepinephrine should be avoided. If further support is necessary, dopamine HCl or dobutamine HCl may be administered. Actual treatment and dosage should depend on the severity of the clinical situation and the judgment and experience of the treating physician.
OVERDOSAGE
Treat all verapamil overdoses as serious and maintain observation for at least 48 hours (especially Calan SR), preferably under continuous hospital care. Delayed pharmacodynamic consequences may occur with the sustained-release formulation. Verapamil is known to decrease gastrointestinal transit time.
Treatment of overdosage should be supportive. Beta-adrenergic stimulation or parenteral administration of calcium solutions may increase calcium ion flux across the slow channel and have been used effectively in treatment of deliberate overdosage with verapamil. In a few reported cases, overdose with calcium channel blockers has been associated with hypotension and bradycardia, initially refractory to atropine but becoming more responsive to this treatment when the patients received large doses (close to 1 gram/hour for more than 24 hours) of calcium chloride. Verapamil cannot be removed by hemodialysis. Clinically significant hypotensive reactions or high degree AV block should be treated with vasopressor agents or cardiac pacing, respectively. Asystole should be handled by the usual measures including cardiopulmonary resuscitation.
DOSAGE AND ADMINISTRATION
The dose of verapamil must be individualized by titration. The usefulness and safety of dosages exceeding 480 mg/day have not been established; therefore, this daily dosage should not be exceeded. Since the half-life of verapamil increases during chronic dosing, maximum response may be delayed.
Angina
Clinical trials show that the usual dose is 80 mg to 120 mg three times a day. However, 40 mg three times a day may be warranted in patients who may have an increased response to verapamil (eg, decreased hepatic function, elderly, etc). Upward titration should be based on therapeutic efficacy and safety evaluated approximately eight hours after dosing. Dosage may be increased at daily (eg, patients with unstable angina) or weekly intervals until optimum clinical response is obtained.
Arrhythmias
The dosage in digitalized patients with chronic atrial fibrillation (see Precautions) ranges from 240 to 320 mg/day in divided (t.i.d. or q.i.d.) doses. The dosage for prophylaxis of PSVT (non-digitalized patients) ranges from 240 to 480 mg/day in divided (t.i.d. or q.i.d.) doses. In general, maximum effects for any given dosage will be apparent during the first 48 hours of therapy.
Essential hypertension
Dose should be individualized by titration. The usual initial monotherapy dose in clinical trials was 80 mg three times a day (240 mg/day). Daily dosages of 360 and 480 mg have been used but there is no evidence that dosages beyond 360 mg provided added effect. Consideration should be given to beginning titration at 40 mg three times per day in patients who might respond to lower doses, such as the elderly or people of small stature. The antihypertensive effects of Calan are evident within the first week of therapy. Upward titration should be based on therapeutic efficacy, assessed at the end of the dosing interval.
HOW SUPPLIED
Calan 40-mg tablets are round, pink, film coated, with CALAN debossed on one side and 40 on the other, supplied as:
| NDC Number | Size |
|---|---|
| 0025-1771-31 | bottle of 100 |
Calan 80-mg tablets are oval, peach colored, scored, film coated, with CALAN debossed on one side and 80 on the other, supplied as:
| NDC Number | Size |
|---|---|
| 0025-1851-31 | bottle of 100 |
| 0025-1851-51 | bottle of 500 |
| 0025-1851-52 | bottle of 1,000 |
Calan 120-mg tablets are oval, brown, scored, film coated, with CALAN 120 debossed on one side, supplied as:
| NDC Number | Size |
|---|---|
| 0025-1861-31 | bottle of 100 |
| 0025-1861-52 | bottle of 1,000 |
Store at 59° to 77°F (15° to 25°C) and protect from light. Dispense in tight, light-resistant containers.
Rx only
LAB-0269-3.0