The Heart: Anti-arrhythmic drugs, Cardiac natriuretic peptides, Anti-anginal drugs. Flashcards
Describe the classification of antidysrhythmic drugs based on their electrophysiological effects proposed by Vaughan Williams?
- Class I: drugs that block voltage-sensitive sodium channels. They are subdivided: Ia, Ib and Ic
- Class II: β-adrenoceptor antagonists.
Class III: drugs that substantially prolong the cardiac action potential. - Class IV: calcium antagonists.
What does emergency treatment of serious dysrhythmias usually involve instead of medications?
Emergency treatment of serious dysrhythmias is usually by physical means (e.g. pacing or electrical cardioversion by applying a direct current shock to the chest or via an implanted device) rather than drugs.
Describe the MOA of Class I anti-arryhthmic drugs?
Describe the MOA of Class I anti-arryhthmic drugs?
- Class I drugs block sodium channels, just as local anaesthetics do, by binding to sites on the α subunit.
- inhibits action potential propagation in excitable cells.
- The characteristic effect on the action potential is to reduce the maximum rate of depo- larisation during phase 0.
Give 2 examples of class Ia anti-arrythmic drugs?
Give 1 example of class Ib anti-arrythmic drugs?
Give 2 examples of class Ic anti-arrythmic drugs?
Class Ia = quinidine and procainamide
**Class Ib **= lidocaine, associate and dis- sociate rapidly within the timeframe of the normal heart- beat.
Class Ic = flecainide and encainide, associate and dissociate much more slowly, thus reaching a steady-state level of block that does not vary appreciably during the cardiac cycle. They markedly inhibit conduction
through the His–Purkinje system.
What are Class II ANTIDYSRHYTHMIC drugs and how do they work?
What are Class III ANTIDYSRHYTHMIC drugs and how do they work?
- 2 examples?
- Effect on cardiac action potential? Effect seen on ECG?
What are Class IV ANTIDYSRHYTHMIC drugs and how do they work?
- 2 examples?
- Which channels do they act on?
How might Lidocaine be used to treat dysrhythmias? What class is it?
- Adverse effects?
Important adverse side effects of β-Adrenoceptor antagonists (class II) drugs?
- 2 examples of β1-selective drugs?
Side effects of Amiodarone? Which class of anti-arrhythmic is it?
Class III
Side effects of Amiodarone? Which class of anti-arrhythmic is it?
Class III
2 Examples of Class IV antidysrhythmic drugs?
How do they each work? Contraindications for each?
DRUGS THAT INCREASE MYOCARDIAL CONTRACTION - CARDIAC GLYCOSIDES
- Cardiac effects?
- Clinically most important example?
- Adverse effects?
Therapeutically the most important cardiac glycoside is digoxin.
MOA of Cardiac glycosides?
What effect does extracellular potassium have on the Effects of cardiac glycosides?
Compare the effects of organic nitrates vs. an arteriolar vasodilator (dipyridamole) on the coronary circulation?
Describe the ntianginal action of nitrates? (3)
The antianginal action of nitrates involves:
* reduced cardiac oxygen consumption, because of reduced cardiac preload and afterload
* redistribution of coronary flow towards ischaemic areas via collaterals
* relief of coronary spasm.
Calcium antagonists
- MOA?
- 3 types/examples?
- Mainly affects which tissues?
- Selectivity of each?
- Vasodilator effect?
- Effects on heart?
- Clinical uses?
- Side effects?
