Torsades de pointes

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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. Magnesium
    1. 1-2gm IV over 1-2 min; then 1-2gm/hr gtt
  2. Overdrive pacing
    1. Goal HR 90-120
  3. Isoproterenol
    1. 2-8 mcg/min

See Also


10/07 DONALDSON (adapted from Tintinalli, Lampe)