Figure 10 Examples of non-methanesulfonanilide IKr blockers.
188.8.131.52.1.4 Class 4: Calcium channel blockers
Verapamil and diltiazem (Figure 11) are not specific for the calcium channels in cardiac tissue. In fact they are more potent on vasculature tissue.
• Effectiveness: Although verapamil has been replaced by adenosine in the treatment of paroxysmal supraventricular nodal tachycardia, it is still useful in controlling ventricular rate in chronic atrial flutter and fibrillation. Verapamil has been used to slow ventricular rate in atrial fibrillation.
• Toxicity: Since the calcium current is important in mediating cardiac contraction and vasoconstriction, calcium channel blockers are associated with negative effects on cardiac contractility and with hypotension.
184.108.40.206.1.5 Class 5: pace maker current (If) blockers: alinidine, falipamil, zatebradine, ZD7288 These drugs, which currently have almost no clinical utility, are classified as Class 5 antiarrhythmics with the prototypical drug being alinidine (Figure 12). Others are zatebradine, falipamil, and ZD7288. They inhibit the pacemaker currents in the SA node and thereby induce bradycardia. However, little is known about their clinical utility.
Figure 11 Examples of class 4 antiarrhythmics (ICa blockers).
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