Treat all verapamil overdoses as serious and maintain observation for at least 48 hours (especially sustained-release verapamil products), preferably under continuous hospital care. Delayed pharmacodynamic consequences may occur with the sustained-release formulations. 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.
COVERA-HS is contraindicated in:
Serious adverse reactions are uncommon when verapamil 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 COVERA-HS occurred at rates greater than 2.0% or occurred at lower rates but appeared drug-related in clinical trials in hypertension and angina:
Placebo n=261 % |
All doses studied n=572 % |
|
Constipation | 2.7 | 11.7* |
Headache | 7.3 | 6.6 |
Upper respiratory infection | 4.6 | 5.4 |
Dizziness | 2.7 | 4.7 |
Fatigue | 3.8 | 4.5 |
Edema | 3.1 | 3.0 |
Nausea | 1.9 | 2.1 |
AV block (1°) | 0.0 | 1.7 |
Elevated liver enzymes (see WARNINGS) | 0.8 | 1.4 |
Bradycardia | 0.4 | 1.4 |
Paresthesia | 0.0 | 1.0 |
Flushing | 0.3 | 0.8 |
Hypotension | 0.0 | 0.7 |
Postural hypotension | 0.3 | 0.4 |
* Constipation was typically mild, easily manageable, and
the incidence usually diminished within about one week. At a typical once-daily
dose of 240 mg, the observed incidence was 7.2%. In previous experience with other formulations of verapamil, the following reactions occurred at rates greater than 1.0% or occurred at lower rates but appeared clearly drug related in clinical trials in 4,954 patients. |
In previous experience with other formulations of verapamil, the following reactions 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% | ||
Hypotension | 2.5% | AV Block total (1°,2°,3°) | 1.2% |
Headache | 2.2% | ||
Edema | 1.9% | AV Block 2° and 3° | 0.8% |
CHF/Pulmonary | |||
Edema | 1.8% | Rash | 1.2% |
Fatigue | 1.7% | Flushing | 0.6% |
Elevated liver enzymes (see WARNINGS) |
The following reactions, reported with orally administered verapamil in 2% or less of patients, occurred under conditions (open trials, marketing experience) where a causal relationship is uncertain; they are listed to alert the physician to a possible relationship:
Cardiovascular: angina pectoris, AV block (2° & 3°), atrioventricular dissociation, CHF, pulmonary edema, 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, psychotic symptoms, shakiness, somnolence, extrapyramidal symptoms.
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.
Other :allergy aggravated, dyspnea.
Treatment Of Acute Cardiovascular Adverse ReactionsThe 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; e.g., intravenously administered norepinephrine bitartrate, atropine sulfate, isoproterenol HCl (all in 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 judgement and experience of the treating physician.
COVERA-HS is indicated for the management of hypertension and angina.
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 human oral 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.
COVERA-HS 180 mg tablets are lavender, round, film coated, with COVERA–HS 2011 printed on one side, supplied as:
NDC Number | Size |
0025-2011-31 | bottle of 100 |
COVERA-HS 240 mg tablets are pale yellow, round, film coated with COVERA–HS 2021 printed on one side, supplied as:
NDC Number | Size | 0025-2021-31 | bottle of 100 |
Store at controlled room temperature 20°–25°C (68°–77°F) . Dispense in tight, light-resistant containers.
Distributed by: G.D. Searle LLC, Division of Pfizer Inc., NY, NY 10017. Revised: Sep 2017
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 previous clinical experience with 4,954 patients primarily with immediate-release verapamil, 1.8% developed congestive heart failure or pulmonary edema. Verapamil should be avoided in patients with severe left ventricular dysfunction (e.g., 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 is started. (Note interactions with digoxin under PRECAUTIONS.)
HypotensionOccasionally, the pharmacologic action of verapamil may produce a decrease in blood pressure below normal levels, which may result in dizziness or symptomatic hypotension. In previous verapamil clinical trials, the incidence observed in 4,954 patients was 2.5%. In clinical studies of COVERA-HS, 0.4% of hypertensive patients and 1.0% of angina patients developed significant hypotension. 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 EnzymesElevations 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 in the face of 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 verapamil.
Atrioventricular BlockThe 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 in previous verapamil clinical trials. 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 upon 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 Formulation SpecificAs with any other non-deformable dosage form caution should be used when administering COVERA-HS in patients with preexisting severe gastrointestinal narrowing (pathologic or iatrogenic). In patients with extremely short GI transit time (<7 hrs), pharmacokinetic data are not available and dosage adjustment may be required.
Use In Patients With Impaired Hepatic FunctionSince 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 TransmissionIt has been reported that verapamil decreases neuromuscular transmission in patients with Duchenne's muscular dystrophy, 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 FunctionAbout 70% of an administered dose of verapamil is excreted as metabolites in the urine. Verapamil is not removed by hemodialysis. 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).
Carcinogenesis, Mutagenesis, Impairment Of FertilityAn 18-month toxicity study in rats, at a low multiple (6-fold) of the maximum recommended human dose, 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.
PregnancyReproduction 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 human oral 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 DeliveryIt 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 MothersVerapamil 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 UseSafety and effectiveness in pediatric patients have not been established.
Geriatric UseClinical studies of COVERA-HS did not include sufficient numbers of subjects under age 65 to determine whether they responded differently from older 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.
COVERA-HS should be administered once daily at bedtime. Clinical trials explored dose ranges between 180 mg and 540 mg given at bedtime and found effects to persist throughout the dosing interval.
COVERA-HS tablets should be swallowed whole and not chewed, broken, or crushed.
For both hypertension and angina, the dose of COVERA-HS should be individualized by titration. Initiate therapy with 180 mg of COVERA-HS.
If an adequate response is not obtained with 180 mg of COVERA-HS, the dose may be titrated upward in the following manner:
When COVERA-HS is administered at bedtime, office evaluation of blood pressure during morning and early afternoon hours is essentially a measure of peak effect. The usual evaluation of trough effect, which sometimes might be needed to evaluate the appropriateness of any given dose of COVERA-HS, would be just prior to bedtime.
Serious adverse reactions are uncommon when verapamil 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 COVERA-HS occurred at rates greater than 2.0% or occurred at lower rates but appeared drug-related in clinical trials in hypertension and angina:
Placebo n=261 % |
All doses studied n=572 % |
|
Constipation | 2.7 | 11.7* |
Headache | 7.3 | 6.6 |
Upper respiratory infection | 4.6 | 5.4 |
Dizziness | 2.7 | 4.7 |
Fatigue | 3.8 | 4.5 |
Edema | 3.1 | 3.0 |
Nausea | 1.9 | 2.1 |
AV block (1°) | 0.0 | 1.7 |
Elevated liver enzymes (see WARNINGS) | 0.8 | 1.4 |
Bradycardia | 0.4 | 1.4 |
Paresthesia | 0.0 | 1.0 |
Flushing | 0.3 | 0.8 |
Hypotension | 0.0 | 0.7 |
Postural hypotension | 0.3 | 0.4 |
* Constipation was typically mild, easily manageable, and
the incidence usually diminished within about one week. At a typical once-daily
dose of 240 mg, the observed incidence was 7.2%. In previous experience with other formulations of verapamil, the following reactions occurred at rates greater than 1.0% or occurred at lower rates but appeared clearly drug related in clinical trials in 4,954 patients. |
In previous experience with other formulations of verapamil, the following reactions 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% | ||
Hypotension | 2.5% | AV Block total (1°,2°,3°) | 1.2% |
Headache | 2.2% | ||
Edema | 1.9% | AV Block 2° and 3° | 0.8% |
CHF/Pulmonary | |||
Edema | 1.8% | Rash | 1.2% |
Fatigue | 1.7% | Flushing | 0.6% |
Elevated liver enzymes (see WARNINGS) |
The following reactions, reported with orally administered verapamil in 2% or less of patients, occurred under conditions (open trials, marketing experience) where a causal relationship is uncertain; they are listed to alert the physician to a possible relationship:
Cardiovascular: angina pectoris, AV block (2° & 3°), atrioventricular dissociation, CHF, pulmonary edema, 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, psychotic symptoms, shakiness, somnolence, extrapyramidal symptoms.
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.
Other :allergy aggravated, dyspnea.
Treatment Of Acute Cardiovascular Adverse ReactionsThe 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; e.g., intravenously administered norepinephrine bitartrate, atropine sulfate, isoproterenol HCl (all in 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 judgement and experience of the treating physician.
DRUG INTERACTIONS Drug- Drug Interactions Effects Of Other Drugs On Verapamil PharmacokineticsIn 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 (e.g., erythromycin, ritonavir) causing elevation of plasma levels of verapamil while inducers of CYP3A4 (e.g., rifampin) have caused a lowering of plasma levels of verapamil.
HMG-CoA Reductase InhibitorsThe use of HMG-CoA reductase inhibitors that are CYP3A4 substrates in combination with verapamil has been associated with reports of myopathy/rhabdomyolysis.
Co-administration of multiple doses of 10 mg of verapamil with 80 mg simvastatin resulted in exposure to simvastatin 2.5-fold that following simvastatin alone. Limit the dose of simvastatin in patients on verapamil to 10 mg daily. Limit the daily dose of lovastatin to 40 mg. Lower starting and maintenance doses of other CYP3A4 substrates (e.g., atorvastatin) may be required as verapamil may increase the plasma concentration of these drugs.
IvabradineConcurrent use of verapamil increases exposure to ivabradine and may exacerbate bradycardia and conduction disturbances. Avoid co-administration of verapamil and ivabradine.
AlcoholVerapamil may increase blood alcohol concentrations and prolong its effects.
AspirinIn a few reported cases, co-administration of verapamil with aspirin has led to increased bleeding times greater than observed with aspirin alone.
Grapefruit JuiceGrapefruit juice may significantly increase concentrations of verapamil. Grapefruit juice given to nine healthy volunteers increased S- and Rverapamil AUC0-12 by 36% and 28%, respectively. Steady state Cmax and Cmin of Sverapamil 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.
Beta-BlockersConcomitant 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 excessive bradycardia and AV block, including complete heart block, when the combination has been used for the treatment of hypertension. For hypertensive patients, the risks 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 and propranolol clearance has been observed when either drug is administered concomitantly with verapamil. A variable effect has been seen when verapamil and atenolol were given together.
DigitalisClinical use of verapamil in digitalized patients has shown the combination to be well tolerated if digoxin doses are properly adjusted. However, 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 kinetics is magnified. Verapamil may reduce total body clearance and extrarenal clearance of digitoxin by 27% and 29%, respectively.
Maintenance and digitalization doses should be reduced when verapamil is administered, and the patient should be reassessed to avoid over- to under-digitalization. Whenever over-digitalization is suspected, the daily dose of digitalis should be reduced or temporarily discontinued. On discontinuation of verapamil use, the patient should be reassessed to avoid under-digitalization. In previous clinical trials with other verapamil formulations related to the control of ventricular response in digitalized patients 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 AgentsVerapamil 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 a 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 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 electrophysiologic 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.
Other AgentsNitrates
Verapamil has been given concomitantly with short- and long-acting nitrates without any undesirable drug interactions. The pharmacologic profile of both drugs and clinical experience suggest beneficial interactions.
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.
Lithium
Increased sensitivity to the effects of lithium (neurotoxicity) has been reported during concomitant verapamil-lithium therapy; lithium levels have been observed sometimes to increase, sometimes to decrease, and sometimes to be unchanged. 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.
Theophylline
Verapamil may inhibit the clearance and increase the plasma levels of theophylline.
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 channel blocking agents, such as verapamil, should each 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.
Telithromycin
Hypotension and bradyarrhythmias have been observed in patients receiving concurrent telithromycin, an antibiotic in the ketolide class.
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.
Mammalian Target Of Rapamycin (mTOR) Inhibitors
In a study of 25 healthy volunteers with co-administration of verapamil with sirolimus, whole blood sirolimus Cmax and AUC were increased 130% and 120%, respectively. Plasma S-(-) verapamil Cmax and AUC were both increased 50%. Co-administration of verapamil with everolimus in 16 healthy volunteers increased the Cmax and AUC of everolimus by 130% and 250%, respectively. With concomitant use of mTOR inhibitors (e.g., sirolimus, temsirolimus, and everolimus) and verapamil, consider appropriate dose reductions of both medications.