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Questions and Answers
What effect do Class I antiarrhythmic drugs have on myocardial membranes?
What effect do Class I antiarrhythmic drugs have on myocardial membranes?
- Block fast Na+ channels (correct)
- Decrease the threshold of excitability
- Enhance conduction velocity
- Increase spontaneous diastolic depolarization
What happens to the blockade of Na+ channels when Class I drugs are used in alkaline blood pH?
What happens to the blockade of Na+ channels when Class I drugs are used in alkaline blood pH?
- There is no effect on blockade
- Blockade is enhanced
- Blockade is decreased (correct)
- Blockade is converted to activated state
What can prolonged procainamide therapy cause?
What can prolonged procainamide therapy cause?
- Atrial fibrillation
- Drug induced Lupus (correct)
- Myocardial infarction
- Ventricular tachycardia
Which statement is true regarding the effective refractory period when Class I drugs are applied?
Which statement is true regarding the effective refractory period when Class I drugs are applied?
What side effect is associated with disopyramide?
What side effect is associated with disopyramide?
What is the effect of Class I drugs on pacemaker cells?
What is the effect of Class I drugs on pacemaker cells?
Which condition exacerbates the rate and frequency of lupus syndrome during procainamide therapy?
Which condition exacerbates the rate and frequency of lupus syndrome during procainamide therapy?
What physiological change occurs when Class I drugs are administered in an acidic blood pH?
What physiological change occurs when Class I drugs are administered in an acidic blood pH?
What type of symptoms may be observed with the use of disopyramide?
What type of symptoms may be observed with the use of disopyramide?
What happens to the conduction velocity when Class I antiarrhythmic drugs act on the myocardial membranes?
What happens to the conduction velocity when Class I antiarrhythmic drugs act on the myocardial membranes?
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Study Notes
Class I Antiarrhythmic Drugs
- All are weak bases
- Bind and block sodium channels in their ionized form
- Acidic blood pH enhances the blockade of Na+ channels
- Alkaline blood pH decreases the blockade of Na+ channels
- Class IA Antiarrhythmic Drugs act on nerve and myocardial membranes to slow conduction by blocking fast Na+ channels
- Class IA Antiarrhythmic Drugs increase the threshold of excitability, increase the effective refractory period, decrease conduction velocity, and decrease spontaneous diastolic depolarization in pacemaker cells
- Prolonged procainamide therapy can cause drug-induced Lupus
- The effects of procainamide are reversed when the drug is removed
- The rate and frequency of lupus syndrome increase with slow acetylators
- Anticholinergic symptoms are seen with disopyramide
Class I Antiarrhythmic Drugs
- Class I antiarrhythmic drugs are weak bases
- They bind and block sodium channels in their ionized form
- Acidic blood pH enhances the blockade of sodium channels
- Alkaline blood pH decreases the blockade of sodium channels
- This can be used as an antidote in case of overdose
- Class IA antiarrhythmic drugs act on nerve and myocardial membranes to slow conduction by blocking fast sodium channels
- They increase the threshold of excitability, increase the effective refractory period, decrease conduction velocity, and decrease spontaneous diastolic depolarization in pacemaker cells
- Prolonged procainamide therapy can cause drug-induced lupus, which is reversible when the drug is removed
- The rate and frequency of lupus syndrome are increased in slow acetylators
- Anticholinergic symptoms are seen with disopyramide
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