Anti arrhythmic drugs

Vaughan-Williams Classification of Anti-arrhythmic Drugs... 

It is customary today to classify anti arrhythmic drugs according to their mechanism of action. This is best defined by intracellular recordings that yield monophasic action potentials. In the accompanying figure, the monophasic action potentials of (A) slow response fiber (SA node) and (B) fast Purkinje fiber are shown. For each description that follows, choose the appropriate drug with which the change in character of the monophasic action potential is likely to be associated... 

I88-E89. The answers arc 188-g 189-b. (Hardman, pp 858-859, 864-865.) It is widely accepted that anti arrhythmic drugs are best classified according to their electro physio logic attributes. This is best accomplished by relating the effects of the different drugs to their actions on Na and Ca channels, which are reflected by changes in the monophasic action potential. Amiodarone blocks Na, Ca, and K currents and markedly prolongs repolarization, particularly in depolarized cells. Hecainide is related... 

It is also very important, if possible, to discontinue or lower the doses of drugs with anticholinergic effects antihistamines, antipsychotics, antidepressants, uro-logic spasmolytics, anti-arrhythmics, drugs for Parkinson s disease and more. Prophylactic treatment against Candida infection, bacteria and caries can also be useful (Mouly et al. 2007). 

De Ponti, F., Poluzzi, E., and Montanaro, N., Organising evidence on QT prolongation and occurrence of Torsades de pointes with non-anti-arrhythmic drugs a call for consensus, Eur. J. Clin. Pharmacol, 57,185-209, 2001. 

Amiodarone is an anti-arrhythmic drug indicated in supraventricular and ventricular arrhythmias. One of the main side-effects is photosensitivity and patients are advised to avoid exposure to sunlight and use sun protection factors. 

Use of a large, lipophilic nitrogenous component results in a 1idocaine like, local anesthetic type cardiac anti-arrhythmic drug, lorcainide (20). Synthesis begins with the Schiff s base (1 ) derived by reaction of p-chloro-aniline and borohydride followed by acylation with phenyl acetyl chloride produces amide 1 . Selective hydrolysis with HBr followed by alkylation with isopropyl bromide completes the synthesis of lorcainide (20). ... 

Vaughan-Wifliams EM. Classification of anti-arrhythmic drugs. In Sandoe E, Elensted-Jensen E, Olesen KH, editors. Cardiac arrhythmias. Sodertalje (Sweden) AB Astra 1970. p. 449-72. 

Procaine is a derivative of p-aminobenzoic acid, and is a one of the oldest used ester-type local anaesthetic agents [1], The compound was originally developed by Einhom [2,3], and later with and Uhlfelder [4]. This anti-arrhythmic drug itself has a short half-life, but is able to form salts with other drugs which causes an increase in the duration of action [5]. 

Lidocaine is also a class Ib anti-arrhythmic drug and is used to treat ventricular arrhythmias. Administered by intravenous infusion it has also been found to have a useful role in the management of acute pain and chronic pain syndromes. 

Harry B van Wezel and Martin Pfaffendorf Antihypertensive drugs Anti-ischaemic therapy Inotropic agents Anti-arrhythmic drugs... 

Volatile anaesthetics, calcium channel-entry blockers, and some anti-arrhythmic drugs may potentiate the negative inotropic effect of the 3-adrenoceptor antagonists. Concomitant digoxin therapy may cause AV dissociation. Potentiation of the hypoglycaemic effects of insulin and oral antidiabetic drugs may occur. 

Table 8.6 Summary of main indications for different classes of anti-arrhythmic drugs...

Figure 8.6 Changes produced by class I and III anti-arrhythmic drugs on the cardiac action potential.

Cardiac arrhythmias are a frequent problem in clinical practice, occurring in up to 25% of patients treated with digitalis, 50% of anesthetized patients, and over 80% of patients with acute myocardial infarction. Arrhythmias may require treatment because rhythms that are too rapid, too slow, or asynchronous can reduce cardiac output. Some arrhythmias can precipitate more serious or even lethal rhythm disturbances—eg, early premature ventricular depolarizations can precipitate ventricular fibrillation. In such patients, anti arrhythmic drugs may be lifesaving. On the other hand, the hazards of anti arrhythmic drugs—and in particular the fact that they can precipitate lethal arrhythmias in some patients—has led to a reevaluation of their relative risks and benefits. In general, treatment of asymptomatic or minimally symptomatic arrhythmias should be avoided for this reason. 

Many factors can precipitate or exacerbate arrhythmias ischemia, hypoxia, acidosis or alkalosis, electrolyte abnormalities, excessive catecholamine exposure, autonomic influences, drug toxicity (eg, digitalis or anti arrhythmic drugs), overstretching of cardiac fibers, and the presence of scarred or otherwise diseased tissue. However, all arrhythmias result from (1) disturbances in impulse formation, (2) disturbances in impulse conduction, or (3) both. 

Synthesis of the anti-arrhythmic drug ajmaline from Rauvolfia plants, an efficient source of several alkaloid types used in therapy, represents an even more advanced study of the total enzymatic synthesis of terpenoid indole alkaloids. Ajmaline is a class I anti-arrhythmic alkaloid because of its activity as heart muscle sodium channels antagonist [35],... 

As with some other quinolones, moxifloxadn also prolongs the QTC interval [265], although the prolongation time of 4—6 ms (i.e., 1.4—1.6% of the starting interval) is relatively minimal. For safety reasons, the treatment of patients with QT interval prolongation and certain cardiac diseases is therefore contraindicated. Other medicaments with a potential for prolonging the QT interval may not be administered simultaneously with moxifloxacin. These indude anti-arrhythmic drugs of class IA (e.g., quinidine, hydroquinidine, disopyramide) and III (e.g., amiodarone, sotalol, dofetilide, ibutilide), intravenous erythromydn, tricyclic anti-depressives, and cisapride etc. 

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