Torsades de pointes

Background

Drugs that inhibit P450

1. erythromycin
2. biaxin
3. ketoconozole
4. itraconozole

• 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.

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

Source

10/07 DONALDSON (adapted from Tintinalli, Lampe)

Authors:

Joe Carpenter, Claire, Jordan Swartz, Kevin Lu, Manpreet Singh, Neil Young, Daniel Ostermayer, Diane Hsu, robot, Ross Donaldson