Data on possible interactions between verapamil and disopyramide phosphate are not available. Therefore, disopyramide should not be administered within 48 hours before or 24 hours after verapamil administration.
A study of 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.
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.
Concomitant use of trandolapril and verapamil hydrochloride extended-release tablets with other antihypertensive agents including diuretics, vasodilators, beta-adrenergic blockers, and alpha-antagonists may result in additive hypotensive effects. There are reports that verapamil may result in higher concentrations of the alpha-agonists prazosin and terazosin.
Dual blockade of the RAS with angiotensin receptor blockers, ACE inhibitors, or aliskiren is associated with increased risks of hypotension, hyperkalemia, and changes in renal function (including acute renal failure) compared to monotherapy. Most patients receiving the combination of two RAS inhibitors do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of RAS inhibitors. Closely monitor blood pressure, renal function and electrolytes in patients on trandolapril and verapamil hydrochloride extended-release tablets and other agents that affect the RAS.
Do not co-administer aliskiren with trandolapril and verapamil hydrochloride extended-release tablets in patients with diabetes. Avoid use of aliskiren with trandolapril and verapamil hydrochloride extended-release tablets in patients with renal impairment (GFR <60 ml/min).
Concomitant therapy with beta-adrenergic blockers and verapamil may result in additive negative effects on heart rate, atrioventricular conduction, and/or cardiac contractility. Drug interaction studies have indicated that the maximum concentrations of metoprolol and propanolol are increased after the administration of verapamil. The use of verapamil in combination with a beta-adrenergic blocker 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.
As with other ACE inhibitors, patients on diuretics, especially those on recently instituted diuretic therapy, may occasionally experience an excessive reduction of blood pressure after initiation of therapy with trandolapril and verapamil hydrochloride extended-release tablets. The possibility of exacerbation of hypotensive effects with trandolapril and verapamil hydrochloride extended-release tablets may be minimized by either discontinuing the diuretic or cautiously increasing salt intake prior to initiation of treatment with trandolapril and verapamil hydrochloride extended-release tablets. If it is not possible to discontinue the diuretic, the starting dose of trandolapril and verapamil hydrochloride extended-release tablets should be reduced (see DOSAGE AND ADMINISTRATION). No clinically significant pharmacokinetic interaction has been found between trandolapril (or its metabolites) and furosemide.
Trandolapril can attenuate potassium loss caused by thiazide diuretics and increase serum potassium when used alone. Use of potassium-sparing diuretics (spironolactone, triamterene, or amiloride), potassium supplements, or potassium-containing salt substitutes concomitantly with ACE inhibitors can increase the risk of hyperkalemia. If concomitant use of such agents is indicated, they should be used with caution and with appropriate monitoring of serum potassium (see PRECAUTIONS).
The 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.
Non-Steroidal Anti-Inflammatory Agents including Selective Cyclooxygenase-2 Inhibitors (COX-2 Inhibitors)
In patients who are elderly, volume-depleted (including those on diuretic therapy), or with compromised renal function, co-administration of NSAIDs, including selective COX-2 inhibitors, with ACE inhibitors, including trandolapril, may result in deterioration of renal function, including possible acute renal failure. These effects are usually reversible. Monitor renal function periodically in patients receiving trandolapril and NSAID therapy.
The antihypertensive effect of ACE inhibitors, including trandolapril may be attenuated by NSAIDs.
Patients taking concomitant neprilysin inhibitors (e.g., sacubitril) may be at increased risk for angioedema (see WARNINGS).
Use of a moderate CYP3A4 inhibitor such as verapamil with flibanserin significantly increases flibanserin concentrations, which can lead to severe hypotension and syncope. Concomitant use is contraindicated (see CONTRAINDICATIONS). Discontinue trandolapril and verapamil hydrochloride extended-release tablets at least 2 weeks prior to starting flibanserin. Do not administer trandolapril and verapamil hydrochloride extended-release tablets within 2 days of discontinuing flibanserin.
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.
Verapamil may increase carbamazepine concentrations during combined therapy. This may produce carbamazepine side effects such as diplopia, headache, ataxia, or dizziness.
Therapy with rifampin may markedly reduce oral verapamil bioavailability. There have been reports that erythromycin and telithromycin may increase concentrations of verapamil.
Phenobarbital therapy may increase verapamil clearance.
Verapamil therapy may increase serum levels of cyclosporin, sirolimus and tacrolimus.
Verapamil therapy may inhibit the clearance and increase the plasma levels of theophylline.
Due to metabolism via the CYP enzyme system, there have been reports that verapamil may increase the concentrations of buspirone, midazolam, almotriptan and imipramine.
Colchicine is a substrate for both CYP3A and the efflux transporter, P-gp. Verapamil is known to inhibit CYP3A and P-gp. When verapamil and colchicine are administered together, the potential inhibition of P-gp and/or CYP3A by verapamil may lead to increased exposure to colchicine (see PRECAUTIONS — Drug Interactions).
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