Torsades de pointes
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)