Med Chem Antiarrhythmics
Terms
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Class 1A
-MOA
-Effect on primarily which ion
-Effect on phase of AP -
*Na+ channel blocker
*Na+ inward
*Phase 0, Lengthens AP - Class 1B
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*Na+ channel blocker
*Na+ inward
*Phase 0, little change in AP length - Class 1C
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Na+ channel blocker
Na+ inward
Phase 0, slows conduction - Class 1 with regards to dissociation rate
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1A= intermediate
1B= Fast (least potent)
1C= slow (most potent) - Class II
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Beta-antagonists (block Beta-receptor on Ca++ channels causing decreased Ca++ influx and increased time required for repolarization in phase II.
Na+ inward, K+ outward
Phases I,II,IV, slows conduction - Class III
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K+ channel blocker
K+ outward
Phase III, lengthens AP - Class IV
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Ca++ channel blockers
Ca++ inward
Phase II, slows conduction - SAR of Na+ channel blockers (Class 1A)
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1. Functional group that mimics Na+ (able to be ionized)
2.Hydrophobic bulk to physically block the Na+ channel - If a class 1A agent is acetylated, what effect does it have on the drug?
- NAPA (N-acetyl procainamide): 25% activity of parent
- SAR of Na+ channel blockers (Class 1B)
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1. Reverse amide
2. Ortho bulk
3. Functional gp that mimics Na+ (able to be ionized=amine,+, Nitrogen,-,)