Asthma, calcium channel blockers

Patients having high plasma renin activity (PRA) (>8 ng/(mLh)) respond best to an ACE inhibitor or a -adrenoceptor blocker those having low PRA (<1 ng/(mLh)) usually elderly and black, respond best to a calcium channel blocker or a diuretic (184). -Adrenoceptor blockers should not be used in patients who have diabetes, asthma, bradycardia, or peripheral vascular diseases. The thiazide-type diuretics (qv) should be used with caution in patients having diabetes. Likewise, -adrenoceptor blockers should not be combined with verapamil or diltiazem because these dmgs slow the atrioventricular nodal conduction in the heart. Calcium channel blockers are preferred in patients having coronary insufficiency diseases because of the cardioprotective effects of these dmgs. 

Their antihypertensive efficacy is comparable to that of (3-adrenergic blockers and angiotensin-converting enzyme (ACE) inhibitors. The choice of a calcium channel blocker, especially for combination therapy, is largely influenced by the effect of the drug on cardiac pacemakers and contractility and coexisting diseases, such as angina, asthma, and peripheral vascular disease. 

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 Propranolol is gradually withdrawn as serum thyroxine levels return to normal.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... 

Each of the cell functions that may become abnormal in patients with asthma depends to some degree on the movement of calcium into cells. The calcium channel blockers have no effect on baseline airway diameter but do significantly inhibit the airway narrowing that is induced by various stimuli. In patients, both nifedipine and verapamil given by inhalation significantly inhibited the bronchoconstriction induced by a variety of stimuli. However, both drugs were much less effective than inhaled albuterol. 

Calcium channel blockers have an intrinsic natriuretic effect therefore, they do not usually require the addition of a diuretic. These agents are useful in the treatment of hypertensive patients who also have asthma, diabetes, angina, and/or peripheral vascular disease. 

Adverse respiratory effects are uncommon with calcium channel blockers. However, three cases of acute broncho-spasm accompanied by urticaria and pruritus have been reported in patients taking verapamil (51), and a patient with Duchenne-type muscular dystrophy developed respiratory failure during intravenous verapamil therapy for supraventricular tachycardia (52). Recurrent exarcer-bations of asthma occurred in a 66-year-old lady with hypertension and bronchial asthma given modified-release verapamil (53). 

Case Conclusion Diuretics and beta-blockers are first-line agents for treating HTN. Because this patient has asthma, beta-blockers should be avoided. Calcium channel blockers are favorable therapeutic options in patients with both angina and HTN. Because her heart rate is low, diltiazem and verapamil are not optimal choices because they can slow down AV nodal conduction. A long-acting dihydrof ridine, amlodipine, was started. 

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. 

Calcium Channel Blockers - The therapeutic value of calcium channel blockers for the treatment of asthma remains unclear however, they are Important invest atlve tools for the study of airway smooth muscle and cell secretion. Nifedipine inhibited calcium lonophore-induced... 

Giving calcium-channel blockers to patients taking theophylline normally has no adverse effect on the control of asthma, despite the small or modest alteration that may occur in serum theophylline levels with diltiazem, felodipine, nifedipine and verapamil. However, there are isolated case reports of unexplained theophylline toxicity in two patients given nifedipine and two patients given verapamiL Isradipine appears not to interact... 

The evidence for this interaction is adequately documented but the results are not entirely consistent. However, the overall picture is that the concurrent use of theophylline and these calcium-channel blockers is normally safe. Despite the small or modest decreases in the clearance or absorption of theophylline seen with diltiazem, felodipine and verapamil, and the quite large reductions in serum levels seen in one study with nifedipine, no adverse changes in the control of the asthma were seen in any of the studies. However, very occasionally and unpredictably theophylline levels have risen enough to cause toxicity in patients given nifedipine (2 case reports) or verapamil (2 case reports), so that it would be prudent to be aware of the possibility of an interaction when these drugs are given. 

Dmgs that help control asthma and act as good maintenance therapy generally reduced the allergen-induced responses, including the late asthmatic response, while agents with minimal effect on these last, such as calcium channel blockers and antihistamines, were not found useful for this purpose (111,112). 

Hoppe M, Harman E, Hendeles L. The effect of inhaled gallopamil, a potent calcium channel blocker, on the late-phase response in subjects with allergic asthma. J Allergy Clin Immunol 1992 89 688-695. 

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