Diltiazem arrhythmia with

Concomitant use of calcium channel blockers (atenolol) Bradycardia and heart block can occur and the left ventricular end diastolic pressure can rise when beta-blockers are administered with verapamil or diltiazem. Patients with preexisting conduction abnormalities or left ventricular dysfunction are particularly susceptible. Recent acute Ml (sotalol) Sotalol can be used safely and effectively in the long-term treatment of life-threatening ventricular arrhythmias following an Ml. However, experience in the use of sotalol to treat cardiac arrhythmias in the early phase of recovery from acute Ml is limited and at least at high initial doses is not reassuring. 

Dihydropyridine channel blockers (e.g., nifedipine) have little benefit on clinical outcomes beyond symptom relief. The role of verapamil and diltiazem appears to be limited to symptom relief or control of heart rate in patients with supraventricular arrhythmias in whom /l-blockers are contraindicated or ineffective. 

The prominent depressant action of verapamil and diltiazem at the SA and A-V nodes finds use in specific arrhythmias. They are of proven efficacy in acute control and long-term management of paroxysmal supraventricular tachycardia (see Chapter 16).Their ability to inhibit conduction at the A-V node is employed in protecting ventricles from atrial tachyarrhythmias, often in combination with digitalis or propranolol. 

Verapamil and diltiazem are prototypic calcium channel blockers. As indicated previously, these drugs influence cardiac function by blocking inward calcium movement through L channels. In so doing they block conduction velocity in SA and AV node cells. They are used therapeutically to treat reentry arrhythmias through the AV node as well as paroxysmal supraventricular tachycardias. In fact, verapamil has been reported to terminate 60-80 percent of paroxysmal supraventricular tachycardias within several minutes. However, because of their potent effect on AV conduction, these drugs are contraindicated in patients with preexisting conduction problems since they may produce complete AV block. 

CALCIUM CHANNEL BLOCKERS SERTINDOLE Plasma concentrations of sertindole are t by diltiazem and verapamil Diltiazem and verapamil inhibit CYP3A4-mediated metabolism of sertindole Avoid co-administration raised sertindole concentrations are associated with an t risk of prolonged Q-T interval and therefore ventricular arrhythmias, particularly torsades de pointes... 

CALCIUM CHANNEL BLOCKERS DANTROLENE Risk of arrhythmias when diltiazem is given with intravenous dantrolene. Risk of 1 BP, myocardial depression and hyperkalaemia when verapamil is given with intravenous dantrolene Uncertain at present Extreme caution must be exercised when administering parenteral dantrolene to patients on diltiazem or verapamil. Monitor BP and cardiac rhythm closely watch for hyperkalaemia... 

Interactions. Several types of drug interfere with lithium excretion by the renal tubules, causing the plasma concentration to rise. These include diuretics (thiazides more than loop type), ACE inhibitors and angiotensin-11 antagonists, and nonsteroidal anti-inflammatory analgesics. Theophylline and sodium-containing antacids reduce plasma lithium concentration. The effects can be important because lithium has such a low therapeutic ratio. Diltiazem, verapamil, carbamazepine and pheny-toin may cause neurotoxicity without affecting the plasma lithium. Concomitant use of thioridazine should be avoided as ventricular arrhythmias may result. 

Four categories of calcium channel blockers can be defined based on their chemical structures and actions diphenylalkylamines, benzothiazepines, dihydropyridines, and bepridil. Both diphenylalkylamines (verapamil) and benzothiazepines (diltiazem) exhibit effects on both cardiac and vascular tissue. With specificity for the heart tissue, these two types of calcium channel blockers can slow conduction through the AV node and are useful in treating arrhythmias. The dihydropyridines (nifedipine is the prototypical agent) are more potent peripheral and coronary artery vasodilators. They do not affect cardiac conduction, but can dilate coronary arteries. They are particularly useful as antianginal agents. Bepridil is unique in that it blocks both fast sodium channels and calcium channels in the heart. All calcium channel blockers, except nimodipine and bepridil, are effective in treating HTN. 

Although earlier trials suggested that verapamil and diltiazem may provide improved benefit in selected patients, the large Incomplete Infarction Trial of European Research Collaborators Evaluating Prognosis post-Thrombolysis (INTERCEPT) has dampened the interest for the use of diltiazem in patients receiving fibrinolytics. In this trial, the use of extended-release diltiazem had no effect on the 6-month risk of cardiac death, MI, or recurrent ischemia. Therefore, the role of verapamil or diltiazem appears to be limited to relief of ischemia-related symptoms or control of heart rate in patients with supraventricular arrhythmias for whom /8-blockers are contraindicated or ineffective. ... 

It is noteworthy that calcium inhibitory compounds with the ability to inhibit %a+ possess the most potent antiarrhythmic activity against both experimental and clinical arrhythmias (126). For example, nifedipine exerts minimal, if any, antiarrhythmic effect against ischemic induced arrhythmias in intact animals (6, 87, 131). Diltiazem and perhexiline, on the other hand, demonstrate variable antiarrhythmic effects dependent upon their dose and the mechanism responsible for arrhythmia production (ischemia, hypoxia, digitalis, aconitine) (102, 126, 151, 152). Only verapamil, which has been investigated in the largest number of experimental and clinical trials, has demonstrated consistent antiarrhythmic activity against cardiac arrhythmias regardless of cause (155) ... 

The manufacturers of sertindole contraindicate the concurrent use of cimetidine, diltiazem, erythromycin, itraconazole, ketoco-nazole, terfenadine and verapamil because of an increased risk of cardiac arrhythmias. Carbamazepine and phenytoin reduce plasma sertindole levels whereas fluoxetine and paroxetine increase them. No clinically relevant interactions occur with alprazolam, antacids, food or tobacco smoking. 

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