Cardiosel Drug Interactions

Catecholamine-depleting drugs (e.g., reserpine): Additive effect when given with beta-blockers. Patients given these drugs should be observed for evidence of hypotension or marked bradycardia, which may produce vertigo, syncope, or postural hypotension.
Calcium channel blockers (e.g., verapamil, diltiazem): May potentiate the depressant effects of beta-blockers on blood pressure, heart rate, cardiac contractility and AV conduction. A calcium channel blocker of the verapamil (phenylalkylamine) type should not be given intravenously to patients taking metoprolol due to the risk of cardiac arrest in this situation. Closely monitor patients taking an oral calcium channel blocker of the verapamil type in combination with metoprolol.
Class I Anti-arrhythmic drugs and Amiodarone: Amiodarone, propafenone and other class I anti-arrhythmic agents (e.g., quinidine, disopyramide) may potentiate the effects of beta-blockers on heart rate and AV conduction.
Clonidine: If a patient is treated concurrently with clonidine and metoprolol, and clonidine is to be discontinued, metoprolol should be withdrawn several days before clonidine. This is because the hypertension that can follow withdrawal of clonidine may be increased in patients receiving concurrent beta-blocker treatment.
CYP2D6 inhibitors: Potent inhibitors of CYP2D6 may increase plasma metoprolol concentration. Strong inhibition of CYP2D6 would result in the change of phenotype into poor metabolizer. Thus, use with caution when coadministering potent CYP2D6 inhibitors with metoprolol. Known clinically significant potent inhibitors of CYP2D6 are antidepressants (e.g., fluoxetine, paroxetine, bupropion), antipsychotics (e.g., thioridazine), antiarrhythmics (e.g., quinidine, propafenone), antiretrovirals (e.g., ritonavir), antihistamines (e.g., diphenhydramine), antimalarials (e.g., hydroxychloroquine, quinidine), antifungals (e.g., terbinafine), and medications for stomach ulcers (e.g., cimetidine).
Digitalis glycosides: Concomitant use may result in excessive bradycardia and/or increase in AV conduction time.
General anesthetics: Some inhalation anesthetics may enhance the cardio depressant effect of beta-blockers.
Hepatic enzyme inducers: Enzyme inducing agents (e.g., rifampicin) may reduce plasma concentrations of metoprolol.
Insulin and oral hypoglycemic drugs: Beta-blockers may be associated with increased or prolonged hypoglycemia in diabetic patients who use insulin. Beta-blockers may also antagonize the hypoglycemic effects of sulfonylureas. The risk of either effect is less with a beta₁-selective drug such as metoprolol than with a non-selective beta-blocker. However, diabetic patients receiving metoprolol should be monitored to ensure that diabetes control is maintained.
Lidocaine (xylocaine): Metoprolol may reduce the clearance of lidocaine, leading to increased lidocaine effects.
Nitroglycerin: May enhance metoprolol's hypotensive effect.
Nonsteroidal anti-inflammatory drugs (NSAIDs) (e.g., indomethacin): May decrease metoprolol's antihypertensive effect.
Prazosin: The acute postural hypotension that can follow the first dose of prazosin may be increased in patients already taking a beta-blocker.
Sympathomimetics: Metoprolol will antagonize the beta₁ effects of sympathomimetic agents but should have little influence on the bronchodilator effects of beta₂-agonists at normal therapeutic doses.
Alcohol: During concomitant ingestion of alcohol and metoprolol the concentration of blood alcohol may reach higher levels and may decrease more slowly.
Other drugs: Other antihypertensive drugs: Additive effect; care should be taken to avoid hypotension. However, combinations of antihypertensive drugs may often be used with benefit to improve control of hypertension.
As beta-blockers may affect the peripheral circulation, exercise caution when drugs with similar activity (e.g., ergotamine) are given concurrently.
Use with caution when beta-blockers are coadministered with sympathetic ganglion blocking agents, other beta blockers (including eye drops), or monoamine oxidase (MAO) inhibitors.