THE CONTENTS OF THE Verelan CAPSULE SHOULD NOT
BE CRUSHED OR CHEWED. Verelan CAPSULES ARE TO BE SWALLOWED WHOLE OR THE ENTIRE
CONTENTS OF THE CAPSULE SPRINKLED ONTO APPLESAUCE (See DOSAGE AND ADMINISTRATION).
GeneralUse in Patients with Impaired Hepatic Function
Since verapamil is highly metabolized by the liver, it should be
administered cautiously to patients with impaired hepatic function. Severe liver
dysfunction prolongs the elimination half-life of immediate-release verapamil to
about 14 to 16 hours; hence, approximately 30% of the dose given to patients
with normal liver function should be administered to these patients. Careful
monitoring for abnormal prolongation of the PR interval or other signs of
excessive pharmacologic effects (see OVERDOSAGE) should be carried out.
Use in Patients with Attenuated (Decreased)
Neuromuscular Transmission
It has been reported that verapamil decreases neuromuscular
transmission in patients with Duchenne's muscular dystrophy, and that verapamil
prolongs recovery from the neuromuscular blocking agent vecuronium and causes a
worsening of myasthenia gravis. It may be necessary to decrease the dosage of
verapamil when it is administered to patients with attenuated neuromuscular
transmission.
Use in Patients with Impaired Renal Function
About 70% of an administered dose of verapamil is excreted as
metabolites in the urine. Until further data are available, verapamil should be
administered cautiously to patients with impaired renal function. These patients
should be carefully monitored for abnormal prolongation of the PR interval or
other signs of overdosage. (See OVERDOSAGE.)
Information for Patients
When the sprinkle method of administration is prescribed, details
of the proper technique should be explained to the patient. (See DOSAGE AND ADMINISTRATION.)
Drug-Drug InteractionsDrug Interactions: Effects of other drugs on
verapamil pharmacokinetics
In vitro metabolic studies indicate
that verapamil is metabolized by cytochrome P450, CYP3A4, CYP1A2, and CYP2C.
Clinically significant interactions have been reported with inhibitors of CYP3A4
(eg, erythromycin, ritonavir) causing elevation of plasma levels of verapamil
while inducers of CYP3A4 (eg, rifampin) have caused a lowering of plasma levels
of verapamil. Hypotension, bradyarrhythmias, and lactic acidosis have been
observed in patients receiving concurrent telithromycin , an antibiotic in the
ketolide class of antibiotics.
Beta Blockers
Concomitant therapy with beta-adrenergic blockers and verapamil
may result in additive negative effects on heart rate, atrioventricular
conduction, and/or cardiac contractility. The combination of sustained-release
verapamil and beta-adrenergic blocking agents has not been studied. However,
there have been reports of excess bradycardia and AV block, including complete
heart block, when the combination has been used for the treatment of
hypertension.
For hypertensive patients, the risk of combined therapy may outweigh the
potential benefits. The combination should be used only with caution and close
monitoring.
Asymptomatic bradycardia (36 beats/min) with a wandering atrial pacemaker has
been observed in a patient receiving concomitant timolol (a beta-adrenergic
blocker) eyedrops and oral verapamil.
A decrease in metoprolol clearance has been reported when verapamil and
metoprolol were administered together. A similar effect has not been observed
when verapamil and atenolol are given together.
Clonidine
Sinus bradycardia resulting in hospitalization and pacemaker
insertion has been reported in association with the use of clonidine
concurrently with verapamil. Monitor heart rate in patients receiving
concomitant verapamil and clonidine.
Digitalis
Consider reducing digoxin dose when verapamil and digoxin are to
be given together. Monitor digoxin level periodically during therapy. Chronic
verapamil treatment can increase serum digoxin levels by 50% to 75% during the
first week of therapy, and this can result in digitalis toxicity. In patients
with hepatic cirrhosis the influence of verapamil on digoxin pharmacokinetics is
magnified. Verapamil may reduce total body clearance and extrarenal clearance of
digoxin by 27% and 29%, respectively. If digoxin toxicity is suspected, suspend
or discontinue digoxin therapy.
In previous clinical trials with other verapamil formulations related to the
control of ventricular response in patients taking digoxin who had atrial
fibrillation or atrial flutter, ventricular rates below 50/min at rest occurred
in 15% of patients, and asymptomatic hypotension occurred in 5% of
patients.
Antihypertensive Agents
Verapamil administered concomitantly with oral antihypertensive
agents (e.g., vasodilators, angiotensin-converting enzyme inhibitors, diuretics,
beta blockers) will usually have an additive effect on lowering blood pressure.
Patients receiving these combinations should be appropriately monitored.
Concomitant use of agents that attenuate alpha-adrenergic function with
verapamil may result in reduction in blood pressure that is excessive in some
patients. Such an effect was observed in one study following the concomitant
administration of verapamil and prazosin.
Antiarrhythmic AgentsDisopyramide
Until data on possible interactions between verapamil and
disopyramide phosphate are obtained, disopyramide should not be administered
within 48 hours before or 24 hours after verapamil administration.
Flecainide
A study in healthy volunteers showed that the concomitant
administration of flecainide and verapamil may have additive effects on
myocardial contractility, AV conduction, and repolarization. Concomitant therapy
with flecainide and verapamil may result in additive negative inotropic effect
and prolongation of atrioventricular conduction.
Quinidine
In a small number of patients with hypertrophic cardiomyopathy
(IHSS), concomitant use of verapamil and quinidine resulted in significant
hypotension. Until further data are obtained, combined therapy of verapamil and
quinidine in patients with hypertrophic cardiomyopathy should probably be
avoided.
The electrophysiological effects of quinidine and verapamil on AV conduction
were studied in 8 patients. Verapamil significantly counteracted the effects of
quinidine on AV conduction. There has been a report of increased quinidine
levels during verapamil therapy.
Nitrates
Verapamil has been given concomitantly with short- and
long-acting nitrates without any undesirable drug interactions. The
pharmacologic profile of both drugs and the clinical experience suggest
beneficial interactions.
Alcohol
Verapamil has been found to significantly inhibit ethanol
elimination resulting in elevated blood ethanol concentrations that may prolong
the intoxicating effects of alcohol. (See CLINICAL PHARMACOLOGY-Pharmacokinetics and Metabolism.)
OtherAspirin
In a few reported cases, coadministration of verapamil with
aspirin has led to increased bleeding times greater than observed with aspirin
alone.
Cimetidine
The interaction between cimetidine and chronically administered
verapamil has not been studied. Variable results on clearance have been obtained
in acute studies of healthy volunteers; clearance of verapamil was either
reduced or unchanged.
Grapefruit juice
Grapefruit juice may significantly increase concentrations of
verapamil. Grapefruit juice given to nine healthy volunteers increased S- and R-
verapamil AUC0-12 by 36% and 28%, respectively. Steady
state Cmax and Cmin of S-verapamil
increased by 57% and 16.7%, respectively with grapefruit juice compared to
control. Similarly, Cmax and Cmin
of R-verapamil increased by 40% and 13%, respectively. Grapefruit juice did not
affect half-life, nor was there a significant change in AUC0-12 ratio R/S compared to control. Grapefruit juice did not
cause a significant difference in the PK of norverapamil. This increase in
verapamil plasma concentration is not expected to have any clinical
consequences.
Lithium
Pharmacokinetic and pharmacodynamic interactions between oral
verapamil and lithium have been reported. The former may result in a lowering of
serum lithium levels in patients receiving chronic stable oral lithium therapy.
The latter may result in an increased sensitivity to the effects of lithium.
Patients receiving both drugs must be monitored carefully.
Carbamazepine
Verapamil therapy may increase carbamazepine concentrations
during combined therapy. This may produce carbamazepine side effects such as
diplopia, headache, ataxia, or dizziness.
Rifampin
Therapy with rifampin may markedly reduce oral verapamil
bioavailability.
Phenobarbital
Phenobarbital therapy may increase verapamil clearance.
Cyclosporine
Verapamil therapy may increase serum levels of
cyclosporine.
Inhalation Anesthetics
Animal experiments have shown that inhalation anesthetics depress
cardiovascular activity by decreasing the inward movement of calcium ions. When
used concomitantly, inhalation anesthetics and calcium antagonists, such as
verapamil, should be titrated carefully to avoid excessive cardiovascular
depression.
Neuromuscular Blocking Agents
Clinical data and animal studies suggest that verapamil may
potentiate the activity of neuromuscular blocking agents (curare-like and
depolarizing). It may be necessary to decrease the dose of verapamil and/or the
dose of the neuromuscular blocking agent when the drugs are used
concomitantly.
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 per day or approximately 1x, 3.5x and 12x, respectively,
the maximum recommended human daily dose (480 mg per 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.
PregnancyPregnancy Category C
Reproduction studies have been performed in rabbits and rats at
oral doses up to 1.5 (15 mg/kg/day) and 6 (60 mg/kg/day) times the maximum
recommended human daily dose, respectively, and have revealed no evidence of
teratogenicity. In the rat, however, this multiple of the human dose was
embryocidal and retarded fetal growth and development, probably because of
adverse maternal effects reflected in reduced weight gains of the dams. This
oral dose has also been shown to cause hypotension in rats. There are no
adequate and well-controlled studies in pregnant women. Because animal
reproduction studies are not always predictive of human response, this drug
should be used during pregnancy only if clearly needed. Verapamil crosses the
placental barrier and can be detected in umbilical vein blood at delivery.
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 HCl 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 efficacy of verapamil in children below the age of 18
years have not been established.
Geriatric Use
Clinical studies of verapamil did not include sufficient numbers
of subjects aged 65 and over to determine whether they respond differently from
younger subjects. Other reported clinical experience has not identified
differences in responses between the elderly and younger patients. In general,
dose selection for an elderly patient should be cautious, usually starting at
the low end of the dosing range, reflecting the greater frequency of decreased
hepatic, renal, or cardiac function, and of concomitant disease or other drug
therapy.
Aging may affect the pharmacokinetics of verapamil. Elimination half-life may
be prolonged in the elderly (see CLINICAL
PHARMACOLOGY, Pharmacokinetics and Metabolism).
Verapamil is highly metabolized by the liver, and about 70% of the
administered dose is excreted as metabolites in the urine. Clinical
circumstances, some of which may be more common in the elderly, such as hepatic
or renal impairment, should be considered (see PRECAUTIONS, General). In general, lower initial doses of
Verelan may be warranted in the elderly (see DOSAGE AND ADMINISTRATION).
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 the rat. Development of
cataracts due to verapamil has not been reported in man.