Prinzmetals or variant angina

FIGURE 103 Verapamil is used in the management of Prinzmetal s or variant angina. ATP = adenosine triphosphate SR = sarcoplasmic reticulum. 

Verapamil can suppress both early and delayed depolarizations and may antagonize slow responses arising in severely depolarized tissue. 

Verapamil s cardiotoxic effects are dose related and usually avoidable. A common error has been to administer intravenous verapamil to a patient with ventricular tachycardia misdiagnosed as supraventricular tachycardia. In this setting, hypotension and ventricular hbrillation can occur. 

Verapamil s negative inotropic effects may limit its clinical usefulness in damaged hearts. Verapamil can lead to atrioventricular block when used in large doses or in patients with partial atrioventricular block. This block can be treated with atropine, beta-receptor stimulants, or calcium. In patients with sinus node disease, verapamil can precipitate sinus arrest. 

Verapamil is absorbed rapidly and completely from the G1 tract after oral administration however, only about 20 to 35% of the drug reaches systemic circulation because of the hrst-pass effect. Verapamil is V-methylated to norverap-amil, which is an active metabolite. The half-lives of 

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Amlodipine is a calcium-channel-blocking agent, which is indicated in the treatment of hypertension, chronic stable angina, and vasospastic (Prinzmetal or variant) angina. The ten Ca2+ channel antagonists that are in chnical use in the... 

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