Potassium channels amiodarone

III Block of repolarizing potassium channels, prolongation of action potential Amiodarone, Dronedarone, Sotalol, Dofetilide, Ibutilide... 

The Vaughan-Williams classification of antiarrhythmic drugs has been criticized for a number of reasons. The classification is based on the effects of drugs on normal, rather than diseased, myocardium. In addition, many of the drugs may be placed into more than one class. For example, the class IA drugs prolong repolarization/refractoriness, either via the parent drug8,9 or an active metabolite,10 and therefore also maybe placed in class III. Sotalol is also a 3-blocker, and therefore fits into class II. Amiodarone inhibits sodium and potassium channels, is a non-competitive inhibitor of 3-receptors, and inhibits calcium... 

III Potassium channel blockade Slows atrioventricular conduction Amiodarone, sotolol... 

Sotalol, bretylium, and amiodarone block potassium channels. 

In contrast, amiodarone and sotalol are effective in most supraventricular and ventricular tachycardias. Amiodarone displays electrophysiologic characteristics consistent with each type of antiarrhythmic drug, ft is a sodium channel blocker with relatively fast on-off kinetics, has nonselec-tive j8-blocking actions, blocks potassium channels, and has slight calcium antagonist activity. The impressive effectiveness and low proarrhythmic potential of amiodarone have challenged the notion that selective ion channel blockade is preferable. Sotalol is a potent inhibitor of outward... 

The authors hypothesized that this patient had a silent mutation in one of the genes coding for the two major potassium channel proteins (IK, or IKg) that are involved in the mode of action of amiodarone. However, they did not present any genetic studies to support this hypothesis. 

III Potassium channel blocking Amiodarone Bretylium Resistant ventricular fibrillation... 

Class III, which is used for certain tachycardia syndromes, includes amiodarone (whose mechanism of action is not clear), potassium-channel blockers and the atypical P-blocker sotalol. 

Type III antiarrhythmics include agents that specifically prolong refractoriness in atrial and ventricular tissue. This class includes very different drugs bretylium, amiodarone, sotalol, ibutilide, and recently, dofetilide they share the common effect of delaying repolarization by blocking potassium channels. The electrophysiologic actions of bretylium are related to its multifaceted pharmacology. 

Amiodarone, a special case Amiodarone is effective in most types of arrhythmias and is considered the most efficacious of all antiarrhythmic drugs. This may be because it has a broad spectrum it blocks sodium, calcium, and potassium channels and beta adrenoceptors. Because of its toxicities, however, amiodarone is usually reserved for use in arrhythmias that are resistant to other drugs. 

Amiodarone causes microcrystalline deposits in the cornea and skin, thyroid dysfunction (hyper- or hypothyroidism), paresthesias, tremor, and pulmonary fibrosis. Amiodarone rarely causes new arrhythmias, perhaps because it blocks calcium channels and beta receptors as well as sodium and potassium channels. 

Drugs that may affect cyclosporine include allopurinol, amiodarone, androgens (eg, danazol, methyltestosterone), anticonvulsants (eg, carbamazepine, phenobarbital, phenytoin), azole antifungals (eg, fluconazole, ketoconazole), beta-blockers, bosentan, bromocriptine, calcium channel blockers, colchicine, oral contraceptives, corticosteroids, fluoroquinolones (eg, ciprofloxacin), foscarnet, HMG-CoA reductase inhibitors, imipenem-cilastatin, macrolide antibiotics, methotrexate, metoclopramide, nafcillin, nefazodone, orlistat, potassium-sparing diuretics, probucol, rifamycins (rifampin, rifabutin), serotonin reuptake inhibitors (SSRIs eg, fluoxetine, sertraline),... 

AMIODARONE POTASSIUM-SPARING DIURETICS Risk of T levels of eplerenone with amiodarone risk of hyperkalaemia directly related to serum levels Calcium channel blockers inhibit CYP3A4-mediated metabolism of eplerenone Restrict dose of eplerenone to 25mg/day. Monitor serum potassium concentrations closely watch for hyperkalaemia... 

Current concepts of resuscitation after local anesthetic cardiotoxicity have been reviewed (17). Vasopressin may be a logical vasopressor in the setting of hypotension, rather than adrenaline, in view of the dysrhythmogenic potential of the latter. Amiodarone is probably of use in the treatment of dysrhythmias. Calcium channel blockers, phenytoin, and bretyllium should be avoided. In terms of new modes of therapy targeted at the specific action of local anesthetics, lipid infusions, propofol, and insulin/ glucose/potassium infusions may all have a role, but further research is necessary. 

Increased risk of toxicity with drugs that alter serum electrolytes (potassium -depleting diuretics, corticosteroids, thiazide and loop diuretics, amphotericin B, quinidine, amiodarone). Blockers of p adrenergic receptors, calcium channels, or acetylcholinesterase increase risk of complete AV block. Drugs which alter Gl absorption may alter bioavallabillty. 

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