E4031

19 Almokalant

19 Almokalant

Figure 9 Examples of class 3 antiarrhythmics (methanesulfonanilide IKr blockers).

• Toxicity: These drugs all induce torsades, the polymorphic ventricular tachycardia related to QT prolongation. Females have longer QT intervals than males, and are more prone to torsades. The mechanism responsible for torsades may be after-depolarizations acting as ectopic foci, or heterogeneity in repolarization causing re-entry. Since the therapeutic value of IKr blockers is limited by proarrhythmic tendencies, they are used only for acute treatment of atrial tachyarrhythmias.

IKr blockade also occurs with other drugs that are not methanesulfonanilde drugs. Such drugs include quinidine (Figure 4), cisapride, sulfamethoxazole, terfenadine, erythromycin, astemizole, ketoconazole, bepridil, and even antimalarials such as halofantrine (Figure 10). Currently such drugs are being withdrawn if an alternative is available that is equally effective, but does not block IKr. Furthermore, current regulations do not allow the introduction of new drugs that block IKr unless there are no alternatives, or they provide overwhelming benefit and save lives.

20 Cisapride

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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