When used simultaneously with carbamazepine in patients with persistent partial epilepsy due to inhibition of the metabolism of carbamazepine in the liver verapamil strengthens its effect (risk of side effects from the central nervous system, such as diplopia, headache, ataxia and dizziness).
With simultaneous application verapamil inhibits the metabolism of cyclosporine in the liver, which leads to a decrease in its excretion and an increase in the concentration in the blood plasma. This is accompanied by increased immunosuppressive action.
With simultaneous application verapamil increases the concentration of theophylline (due to lower clearance).
With the simultaneous use of verapamil with quinidine, the concentration of quinidine in the blood plasma increases(the risk of a marked decrease in blood pressure especially in patients with hypertrophic obstructive cardiomyopathy).
With simultaneous application verapamil increases the concentration of ethanol in blood plasma and lengthens its effect.
Because the verapamil inhibits the isoenzyme of supSa4, which is involved in the metabolism of atorvastatin, lovastatin and simvastatin, there may be manifestations of drug interaction caused by an increase in the concentrations of statins in the blood plasma (rhabdomyolysis).
With simultaneous application verapamil increases the concentration in the blood plasma of almotriptan, glibenclamide.
With simultaneous application verapamil increases the concentration in blood plasma of sirolimus and tacrolimus.
With simultaneous application verapamil increases the concentration of cardiac glycosides (requires careful monitoring and reduction of the dose of glycosides). With simultaneous application verapamil increases the concentration of metoprolol and propranolol in patients with angina.
With simultaneous application verapamil increases the plasma concentration of colchicine (a substrate for the isoenzyme of syrPa and p-glycoprotein).
With the simultaneous use of verapamil with doxorubicin, the concentration of doxorubicin in the blood plasma increases and its effectiveness increases.
With the simultaneous use of verapamil with imipramine, the concentration of imipramine in the blood plasma increases (the risk of unwanted changes caused by additive inhibitory action, verapamil and imipramine on AVconductivity). Does not affect the concentration of the active metabolite, desipramine.
Verapamil increases the concentration of prazosin and terazosin with simultaneous use (risk of development of severe arterial hypotension).
With the simultaneous use of verapamil with buspirone or midazolam, their concentration in the blood plasma increases (the risk of side effects). Inhibitors of supSa4 (including erythromycin, human immunodeficiency virus protease inhibitors), telithromycin increase plasma concentrations of verapamil.
Grapefruit juice increases the concentration in the blood plasma r- and s-isomer of verapamil.
Cimetidine either does not alter, or reduces the clearance of verapamil (possibly enhancing the effects of verapamil).
Rifampicin can significantly reduce bioavailability (up to 92%), as well as the concentration of verapamil in blood plasma, which leads to a decrease in its clinical effectiveness.
Phenobarbital increases the clearance of verapamil 5 times.
Sulfinpyrazone increases the clearance of verapamil by about 3 times and reduces bioavailability to 60%.
Preparations of St. John's wort penetrate reduce the concentration r- and sisomer of verapamil in blood plasma.
With the simultaneous use of verapamil with inhalational anesthetics, the risk of developing bradycardia, atrioventricular blockade, and heart failure is increased. The combination of verapamil with beta-blockers can lead to an increase in the negative inotropic effect, an increased risk of developing atrioventricular conduction disorders, bradycardia (verapamil and beta-blockers should be used at intervals of several hours).
Prazosin and other alpha-blockers, as well as other antihypertensive drugs (angiotensin-converting enzyme inhibitors, vasodilators, diuretics, beta-adrenoblockers) increase the antihypertensive effect of verapamil.
With the simultaneous use of verapamil with disopyramide and flecainide, severe arterial hypotension and collapse are possible, up to a lethal outcome.The risk of developing severe manifestations of drug interaction is associated with an increase in the negative inotropic effect. Do not administer dysopyramide and flecainide for 48 hours before or 24 hours after the use of verapamil, Verapamil increases the risk of neurotoxic effect of lithium preparations.
Verapamil enhances the effect of peripheral muscle relaxants (may require a change in the dosage regimen).
With the simultaneous use of verapamil with acetylsalicylic acid, cases of increased bleeding time are described.