Channel Blocking Drugs

Calcium channel blocking drug s—for example, amlodipine (Norvasc) and diltiazem (Cardizem)... 

Today, this group is represented by a single calcium channel-blocking drug, verapamil, which is primarily used as an antianginal drug as well as for controlling hypertension. 

Certain drugs tend to produce hyperglycemia and may lead to loss of blood glucose control. These drugs include the thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blocking drugs, and isoniazid. 

The effects of the prototypical calcium channel blockers are seen most prominently in the cardiovascular system (Table 19.1), although calcium channels are widely distributed among excitable cells. The following calcium channel-blocking drugs are clinically the most widely used compounds in this very extensive class of pharmacological agents amlodipine, diltiazem, isradipine, nifedipine, nicardipine, nimodipine, and verapamil. 

Table 12-5 Clinical Pharmacology of Some Calcium Channel-Blocking Drugs. ...

Treatment of atrial fibrillation is initiated to relieve patient symptoms and prevent the complications of thromboembolism and tachycardia-induced heart failure, the result of prolonged uncontrolled heart rates. The initial treatment objective is control of the ventricular response. This is usually achieved by use of a calcium channel-blocking drug alone or in combination with a 13-adrenergic blocker. Digoxin may be of value in the presence of heart failure. A second objective is a restoration and maintenance of normal sinus rhythm. Several studies show that rate control (maintenance of ventricular rate in the range of 60-80 bpm) has a better benefit-to-risk outcome than rhythm control (conversion to normal sinus rhythm) in the long-term health of patients with atrial fibrillation. If rhythm control is deemed desirable, sinus rhythm is usually restored by DC cardioversion in the USA in... 

Several isoforms of the sodium channel have been identified, and they have differing sensitivities to channel-blocking drugs such as tetrodotoxin. There is also evidence that some sodium channels are much more sensitive to local anesthetics than the classic channels associated with axonal transmission. 

Lidocaine is chemically similar to cocaine it is also a sodium channel-blocking drug, which is why it is an effective topical pain reliever that is commonly sold over the counter in drug stores. However, in contrast to cocaine, it has no reinforcing, euphoric effect at all, and animals, including humans, will not self-administer it. This confirms the validity of the finding that... 

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