Pharmacology Flashcards
what is an inotropic drug?
affects contractility of the heart
-alters force/energy of muscular contractions
what is a chronotropic drug?
affects HR
outline the classes of anti-arrhythmic drugs
classified according to their effects on cardiac action potential
outline cardiac action potential electrophysiology
how do class 1 anti-arrhythmics work
work by blocking Na channels - slow depoalrisation & conduction
give an example of class 1a anti-arrhythmic drug
Quinidine
v rarely used in UK due to adverse effects - may cause prolonged QT
outline 2 class 1b anti-arrhythmic drugs
- lidocaine
- phenytoin
outline a class 1c anti-arrhythmic drug
in who can this class not be given?
Flecainide
MARKEDLY depresses sodium entry into channels
In pts with CAD
adverse affects of class 1?
- class 1 b&cā> neurotoxicity
- negatively inotropic
- N&V
what are class 2 anti-arrhythmics?
beta-blockers
how do beta blockers act? and effects?
- act to reduce sympathetic activity
- negatively inotropic & chronotropic
- act on AV node to reduce conduction
- act on SA node to reduce rate of spontaneous depolarisation
adverse effects of beta blockers?
- postural hypotension
- bradycardia
- AV node block
- bronchoconstriction
- hypoglycaemia
- erectile dysfunction
- insomnia
outline class III anti-arrhythmic drugs
amiodarone
sotalol
mechanism of action of class III anti-arrhythmic drugs
block K channels - hence cause prolongation of refractory period
adverse effects of amiodarone?
- thyroid dysfunction
- peripheral neuropathy
- photosensitivity
- lung fibrosis
- hepatitis /cirrhosis
what are class 4 anti-arrhythmics?
Non-Dihydropyridine CCBs
mechanism of action of non-dihydropyridine CCBs?
- reduce conduction through AV node
- negative inotropes
- negative chronotropes
adverse effects of non-dihydropyridine CCBs
- bradycardia
- heart block
- constipation
- gum hyperplasia
- headaches, flushing, peripheral oedema
- more common in dihydropyridines
outline the classification of CCBs
- Dihydropyridines
- amlodipine
- nifedipine
- Non-Dihydropyridines
- verapamil
- diltiazem
what are the different properties of the classes of CCB
- Dihydropyridine
- anti-hypertensive properties
- Non-Dihydropyridine
- anti-arrhythmic properties
what is Digoxin?
- cardiac glycoside
- Na/K ATPase inhibitor
mechanism of action of Digoxin?
- slows AV conduction
- positive inotrope
adverse effects of digoxin?
- causes ECG changes
- toxicity may cause PR prolongation & lead to arrhythmias
- hypokalaemia potentiates its effects
action of adenosine?
acts on SA node to reduce HR, and AV node to slow conduction
used primarily in SVT
mechanism of action of atropine?
anti-cholinergic
mode of action of aspirin?
- cyclo-oxygenase inhibitor
- inhibits production of thromboxane A2
- reduces platelet aggregation
mode of action of clopidogrel?
- ADP receptor antagonist
- reduces platelet aggregation
mechanism of action of nitrates?
- release NO to relax smooth muscle
- venodilators
outline cardioselective beta blockers
Betablockers Act Exclusively At Myocardium
Betaxolol
Acebutelol
Esmolol
Atenolol
Metoprolol
what is the stance of cardioselective b-blockers in pts with asthma
Cardioselective beta-blockers pose a lesser risk but this risk is invariably dose-dependent. beta blockers should still be avoided in these patients.
diabetics and beta blockers consideration?
due to the risk of hypoglycaemia, beta blockers may mask the symptoms of a hypo in a diabetic
what CCBs are used for treatment of stable angina?
why do they work in preventing angina?
ALL
They reduce cardiac rate, contractility and afterload and hence myocardial oxygen demand - preventing angina
outline the main difference between dihydropiridine & non-duhydropyridine CCB in terms of where they act
- dihydro- relatively selective for the vasculature
- non-dihydro- more selective for the heart
- verapamil MOST cardioselective
what must you not co-prescribe with beta blockers?
non-dihydropyridine CCB ā> may cause bradycardia, asystole etc
