Interactions : אינטראקציות

4.5 Interaction with other medicinal products and other forms of interaction

In rare instances, including when patients with severe cardiomyopathy, congestive heart failure or recent myocardial infarction were given intravenous beta-adrenergic blocking agents or disopyramide concomitantly with intravenous verapamil hydrochloride, serious adverse effects have occurred. Concomitant use of verapamil hydrochloride injection with agents that decrease adrenergic function may result in an exaggerated hypotensive response.

In vitro metabolic studies indicate that verapamil hydrochloride is metabolized by cytochrome P450 CYP3A4, CYP1A2, CYP2C8, CYP2C9 and CYP2C18. Verapamil has been shown to be an inhibitor of CYP3A4 enzymes and P-glycoprotein (P-gp). Clinically significant interactions have been reported with inhibitors of CYP3A4 causing elevation of plasma levels of verapamil hydrochloride while inducers of CYP3A4 have caused a lowering of plasma levels of verapamil hydrochloride, therefore, patients should be monitored for drug interactions.
The following are potential drug interactions associated due to pharmacokinetic reasons: Acetylsalicylic acid
Concomitant use of verapamil with aspirin may increase the risk of bleeding Alcohol
Increase in blood alcohol has been reported.
Alpha blockers
Verapamil may increase the plasma concentrations of prazosin and terazosin which may have an additive hypotensive effect.
Antiarrhythmics
Verapamil may slightly decrease the plasma clearance of flecainide whereas flecainide has no effect on the verapamil plasma clearance.
Verapamil may increase the plasma concentrations of quinidine. Pulmonary oedema may occur in patients with hypertrophic cardiomyopathy
The combination of verapamil and antiarrhythmic agents may lead to additive cardiovascular effects (e.g. AV block, bradycardia, hypotension, heart failure).
Anticonvulsants
Verapamil may increase the plasma concentrations of carbamazepine. This may produce side effects such as diplopia, headache, ataxia or dizziness. Phenytoin may decrease the plasma concentrations of verapamil.
Antidepressants
Verapamil may increase the plasma concentrations of imipramine.
Antidiabetics
Verapamil may increase the plasma concentrations of glibenclamide (glyburide). Co-administration of verapamil with metformin may reduce the efficacy of metformin.
Antihypertensives, diuretics, vasodilators
Potentiation of the hypotensive effect.
Anti-infectives
Rifampicin may reduce the plasma concentrations of verapamil which may produce a reduced blood pressure lowering effect. Erythromycin, clarithromycin and telithromycin may increase the plasma concentrations of verapamil.
Antineoplastics
Verapamil may increase the plasma concentrations of doxorubicin.
Barbiturates
Phenobarbital may reduce the plasma concentrations of verapamil.
Benzodiazepines and other anxiolytics
Verapamil may increase the plasma concentrations of buspirone and midazolam.
Beta blockers
Verapamil may increase the plasma concentrations of metoprolol and propranolol which may lead to additive cardiovascular effects (e.g. AV block, bradycardia, hypotension, heart failure).
Intravenous beta-blockers should not be given to patients under treatment with verapamil.
Cardiac glycosides
Verapamil may increase the plasma concentrations of digitoxin and digoxin. Verapamil has been shown to increase the serum concentration of digoxin and caution should be exercised with regard to digitalis toxicity. The digitalis level should be determined and the glycoside dose reduced, if required.
Colchicine
Colchicine is a substrate for both CYP3A and the efflux transporter, P-glycoprotein (P-gp). Verapamil is known to inhibit CYP3A and P-gp. When verapamil and colchicine are administered together, inhibition of P-gp and/or CYP3A by verapamil may lead to increased exposure to colchicine. Combined use is not recommended.
H2 Receptor antagonists
Cimetidine may increase the plasma concentrations of verapamil.
HIV antiviral agents
Due to the metabolic inhibitory potential of some of the HIV antiviral agents, such as ritonavir, plasma concentrations of verapamil may increase. Caution should be used or dose of verapamil may be decreased.
Immunosuppressants
Verapamil may increase the plasma concentrations of ciclosporin, everolimus, sirolimus and tacrolimus.
Concentration determinations and dose adjustments of everolimus and sirolimus may be necessary.
Lipid lowering agents
Verapamil may increase the plasma concentrations atorvastatin, lovastatin and simvastatin.
Treatment with HMG CoA reductase inhibitors (e.g., simvastatin, atorvastatin or lovastatin) in a patient taking verapamil should be started at the lowest possible dose and titrated upwards. If verapamil treatment is to be added to patients already taking an HMG CoA reductase inhibitor (e.g., simvastatin, atorvastatin or lovastatin), consider a reduction in the statin dose and re-titrate against serum cholesterol concentrations.
Atorvastatin has been shown to increase verapamil levels. Although there is no direct in vivo clinical evidence, there is strong potential for verapamil to significantly affect atorvastatin pharmacokinetics in a similar manner to simvastatin or lovastatin. Consider using caution when atorvastatin and verapamil are concomitantly administered.
Fluvastatin, pravastatin and rosuvastatin are not metabolized by CYP3A4 and are less likely to interact with verapamil.
Lithium
Serum levels of lithium may be reduced. However, there may be increased sensitivity to lithium causing enhanced neurotoxicity. Patients receiving both drugs should be monitored carefully.
Neuromuscular blocking agents employed in anaesthesia
The effects may be potentiated.
Serotonin receptor agonists
Verapamil may increase the plasma concentrations of almotriptan.
Theophylline
Verapamil may increase the plasma concentrations of theophylline.
Uricosurics
Sulfinpyrazone may reduce the plasma concentrations of verapamil which may produce a reduced blood pressure lowering effect. When verapamil and sulfinpyrazone are administrated together, there is no change in PK.
Anticoagulants
When oral verapamil was co-administered with dabigatran etexilate (150 mg), a P-gp substrate, the Cmax and AUC of dabigatran were increased but magnitude of this change differs depending on time between administration and the formulation of verapamil. Co-administration of verapamil 240 mg extended-release at the same time as dabigatran etexilate resulted in increased dabigatran exposure (increase of Cmax by about 90% and AUC by about 70%).
Close clinical surveillance is recommended when verapamil is combined with dabigatran etexilate and particularly in the occurrence of bleeding, notably in patients having a mild to moderate renal impairment.
Other Cardiac therapy
Concomitant use with ivabradine is contraindicated due to the additional heart rate lowering effect of verapamil to ivabradine (see section 4.3).
Other
St. John's Wort may reduce the plasma concentrations of verapamil, whereas grapefruit juice may increase the plasma concentrations of verapamil.