Question | Answer |
Class I antiarrhythmics are | sodium channel blockers, may increase heart rate |
Class 1A (quinidine, norpace) | reduce rate of firing of ectopic foci, increase the effective refractory period, reduce the speed of conduction |
Class 1B (mexiletine) | block both activated and inactivated sodium channels |
Class 1C (propafenone [Rythmol],flecainide [Tambocor]) | primarily block the sodium fast channel during phase 0 of the action potential, reserved for pts with severe ventricular arrhythmias when other drugs have not worked |
Class II: beta blockers | mask s/s of hypoglycemia except diaphoresis |
Class III: (sotalol, amiodarone) | prolong the effective refractory period by some mechanism other than sodium channel blockade, often by blocking K channels which result in decreased rate of ventricular ectopic beats |
Class IV: CCB's | |
only short acting antiarrhythmic | procainamide |
Things to consider about amiodarone | inhibits the enzyme that converts T4 to T3 and iodine is a major component of this drug; about 5% of pts with inderlying predisposition to thyroid disease may develop thyrotoxicosis of hypothyroidism (also propranolol) |
amiodarone | pulmonary fibrosis occurs in 5-15% of pts and use in pulmonary disease is questioned |
amiodarone | extrapyramidal side effects, hepatitis, epididymitis, corneal and skin deposits, peripheral neuropathy, and photosensitivity |
grapefruit juice inhibits the ? | CYP 3A4 system |
clinical use | Atrial arrhythmias, ventricular arrhythmias |
amiodarone | has effect in all classes; has been shown to reduce mortality in cardiac arrest survivors from 50 to 20% at 2years post cardiac arrest |
K levels should be kept above ? in pts with rhythm disturbances | 4 mEq/L K concentration in the ECF is the jamor determinant of resting membrane potential and membrane stability |