week 8 Flashcards
examples of Class 1A antiarrhythmics
Disopyranamide
Quinidine
Procainamide
mechanism of action of class 1A antiarrhythmics
Blocks fast Na channels.
Prolongs phase 0 in non pacemaker cardiac cells.
prolongs action potential and refractory period.
Also has potassium channel blockade
example of class 1B antiarrhythmic
lignocaine
mechanism of action of class 1B antiarrythmic
weak blockade of Na channels.
preferentially bind to inactive Na channels of ischaemic tissue.
Prolongs phase 0 and shortens phase 3, decreases the AP.
indication of class 1B antiarrhythmics
Ventricular arrhythmias
example of class 1C antiarrhythmic
Flecainide
mechanism of action of of flecainide
block fast Na channels during phase 0.
Slow dissociation kinetics, binds and unbinds slowly.
Profound suppression of conduction in accessory pathways and ectopic foci.
No effect on AP or QT.
what can flecainide interact with?
Digoxin
Increases levels by 15%
mechanism of action of amiodarone
Class 3 anti-arrhythmic - blocks K channel.
Also has Class 1,2 and 4 properties.
Prolongs phase 3 of AP, increase AP,ERP, QTi.
Main effect is delaying repolarization to prevent re-entry arrhythmias.
elimination of amiodarone
half life has 2 phases, 50% 3-10 days. remainder over several weeks to months.
excreted in bile and faeces.
accumulates in tissues.
adverse effects of amiodarone
Pulmonary fibrosis, can be fatal.
Hypo/hyper thyroidism.
Photosensitivity, blue grey skin.
Ataxia, peripheral neuropathy.
Hepatotoxicity.
Bradycardia.
mechanism of action of Sotalol
Class 3 antiarrhythmic - blocks K channels.
Also has Class 2 properties - Beta blocker.
Prolongs phase 3 repolarisation, increases AP and QTi.
Decrease heart rate, AV node conduction.
adverse reactions of Sotalol
Increases QT interval, high risk of torsades de point.
especially in renal impairment, hypokalaemia, high doses.
pharmacokinetics of Sotalol
oral or IV.
Not metabolised, renally excreted.
Onset 1-2 hours.
t1/2 12 hours.
contraindications of sotalol
long QT syndrome.
Bradycardia.
Asthma/COPD.
Renal failure.
what are class 4 antiarrhythmics
Calcium channel blockers
mechanism of action of CCB
Block L-type voltage gated Ca channels
Reduce Ca influx in cardiac myocytes, nodal tissues, vascular smooth muscle.
subtypes of CCB
Dihydropyridines and non dihydropyridines
examples of dihydropyridine CCB
Amlodipine, nifedipine
main effects of dihydropyridine CCB
vasodilation, decreasing BP.
used in HTN and angina.
Blocks vascular Ca channels
main effects of non dihydropyridines CCB
decrease HR and contractility
used in SVT, AF, angina.
Block cardiac Ca channels.
mechanism of action of verapamil
non dihydropiridine CCB.
blocks L type calcium channels in SA node, AV node, myocardium.
Reduce Ca influx.
Negative inotrope.
contraindications of verapamil
avoid in HFrEF
Heart block, bradycardia
Beta blocker use
pharmacokinetics of verapamil
oral or IV.
highly protein bound.
hepatic metabolism.
half life 4-7 hours.
urinary and foecal excretion.
