Torsades de pointes

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Background

Drugs that inhibit P450

- erythromycin

- biaxin

- ketoconozole

- itraconozole

Treatment

1) Mg (1-2gm over 1-2 minutes; then, 1-2gm/hr gtt)

2) Overdrive pacing (hr = 90-120)

3) Isoproterenol (if no pacing, 2-8 mcg/min)

4) lidocaine

- certain antihistamines like terfandadine or astemizole, inhibit the delayed rectifier potassium channel

- terfenadine is completely metabolized in liver. Once metabolized, has no cardiac activity

- unmetabolized terfenadine has quinidine- like activity- gives torsades

- if P450 enz inhibited by other drug, then will have increase in concentration of unmetabolized terfanadine.



Source

10/07 DONALDSON (adapted from Tintinalli, Lampe)