Calcium channel blockers contraindications

In randomized, controlled, clinical trials, calcium channel blockers were as effective as p-blockers at preventing ischemic symptoms. Calcium channel blockers are recommended as initial treatment in IHD when /3-blockers are contraindicated or not tolerated. In addition, CCBs may be used in combination with /3-blockers when initial treatment is unsuccessful. However, the combination of a (1-blocker with either verapamil or diltiazem should be used with extreme caution since all of these drugs decrease AV nodal conduction, increasing the risk for severe bradycardia or AV block when used together. If combination therapy is warranted, a long-acting dihydropyridine CCB is preferred. (3-Blockers will prevent reflex increases in sympathetic tone and heart rate with the use of calcium channel blockers with potent vasodilatory effects. 

Current data suggest little benefit on clinical outcomes beyond symptom relief for calcium channel blockers in the setting of ACS.43 Moreover, the use of first-generation shortacting dihydropyridines, such as nifedipine, should be avoided because they appear to worsen outcomes through their negative inotropic effects, induction of reflex sympathetic activation, tachycardia, and increased myocardial ischemia.43 Therefore, calcium channel blockers should be avoided in the acute management of MI unless there is a clear symptomatic need or a contraindication to p-blockers. 

Adverse effects and contraindications of calcium channel blockers are described in Table 5-2. Verapamil, diltiazem, and first-generation dihydropyridines should also be avoided in patients with acute decompensated heart failure or left... 

As described in the previous section, calcium channel blockers should not be administered to most patients with ACS. Their role is a second-line treatment for patients with certain contraindications to P-blockers and those with continued ischemia despite P-blocker and nitrate therapy. Administration of either amlodipine, diltiazem, or verapamil is preferred.2 Agent selection is based on heart rate and left ventricular dysfunction (diltiazem and verapamil are contraindicated in patients with bradycardia, heart block, or systolic heart failure). Dosing and contraindications are described in Table 5-2. 

Although P-blockers should be avoided in patients with decompensated heart failure from left ventricular systolic dysfunction complicating an MI, clinical trial data suggest that it is safe to initiate P-blockers prior to hospital discharge in these patients once heart failure symptoms have resolved.64 These patients may actually benefit more than those without left ventricular dysfunction.65 In patients who cannot tolerate or have a contraindication to a P-blocker, a calcium channel blocker can be used to prevent anginal symptoms, but should not be used routinely in the absence of such symptoms.2,3,62... 

In the setting of STE ACS, calcium channel blockers are reserved for patients who have contraindications to //-blockers. They are used for relief of ischemic symptoms only. 

Patients who had been prescribed calcium channel blockers for hypertension who are not receiving //-blockers and who do not have a contraindication should have the calcium channel blocker discontinued and a //-blocker initiated. 

A calcium channel blocker can be used to prevent anginal symptoms in patients who cannot tolerate or have a contraindication to a /1-blocker but should not be used routinely in the absence of such symptoms. 

In patients with unstable angina, immediate-release short-acting calcium channel blockers can increase the risk of adverse cardiac events and therefore are contraindicated (see Toxicity, above). However, in patients with non-Q-wave myocardial infarction, diltiazem can decrease the frequency of postinfarction angina and may be used. 

During the acute phase of thyrotoxicosis, B-adrenoceptor blocking agents without intrinsic sympathomimetic activity are extremely helpful. Propranolol, 20-40 mg orally every 6 hours, will control tachycardia, hypertension, and atrial fibrillation. Propranolol is gradually withdrawn as serum thyroxine levels return to normal. Diltiazem, 90-120 mg three or four times daily, can be used to control tachycardia in patients in whom blockers are contraindicated, eg, those with asthma. Other calcium channel blockers may not be as effective as diltiazem. Adequate nutrition and vitamin supplements are essential. Barbiturates accelerate T4 breakdown (by hepatic enzyme induction) and may be helpful both as sedatives and to lower T4... 

Calcium channel blockers can also be given to treat stable angina, especially if beta blockers are not tolerated or are contraindicated in specific patients.13 These drugs decrease cardiac workload directly by limiting calcium entry into myocardial cells and indirectly by producing peripheral vasodilation, thus decreasing cardiac preload and afterload.47 Hence, cal-... 

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. 

B Because this patient has asthma and is wheezing, calcium channel blockers are the drug class of choice. Unlike beta-blockers and adenosine, they do not cause bronchospasm. Beta-blockers and adenosine should be used cautiously in patients with obstructive lung disease, and use should be avoided in patients with asthma. Digoxin is not contraindicated, but it is not the drug of choice due to its slow onset. Amiodarone is indicated for ventricular arrhythmias, but not PSVT. 

Good candidates for calcium channel blockers in angina include patients with contraindications to or intolerance of /3-blockers, those with coexisting conduction system disease (except for verapamil and diltiazem), those with Prinzmetal s angina (vasospastic or variable-threshold angina), those with peripheral vascular disease, those with severe ventricular dysfunction (amlopidine is probably the calcium channel blocker of choice, and others need to be used with caution if the ejection fraction is less than 40%), and those with concurrent hypertension. 

Adverse effects and contraindications of calcium channel blockers are described in Table 16. Verapamil, diltiazem, and first-generation dihydropyridines also should be avoided in patients with acute decompensated heart failure or LV dysfunction because they can worsen heart failure and potentially increase mortality secondary to their negative inotropic effects. In patients with heart failure requiring treatment with a calcium channel blocker, amlodipine is the preferred agent. ... 

The calcium channel blockers generally are considered seconder third-line options for preventive treatment when other drugs with established clinical benefit are ineffective or contraindicated. Verapamil is the most widely used calcium chaimel blocker for preventive treatment, but it provided only modest benefit in decreasing the frequency of attacks in two placebo-controlled studies." The therapeutic effect of verapamil may not be noted for up to 8 weeks after initiation of therapy. Side effects of verapamil may include constipation, hypotension, bradycardia, atrioventricular block, and exacerbation of congestive heart failure. Evaluations of nifedipine, nimodipine, diltiazem, and nicardipine have yielded equivocal results. ... 

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