Torsades de pointes

Revision as of 17:59, 12 March 2011 by Rossdonaldson1 (talk | contribs)


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.


  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


10/07 DONALDSON (adapted from Tintinalli, Lampe)