Anti-arrythmias

Question 1

Lidocaine

• Class
• mechanism
• What it’s used for
• side effects
• drug drug interactions

Answer 1

1B - Na+ channel blocker
Slower depolarisation slower movement of action potentials through the myocardium
Reduces recent rant circuits
Lidocaine reduces effective refractory period which is good as it reduces risk of after depolarisations
Used to treat recent rant tachycardias. Also used in Dentistry, anaesthesia (ointments or surgery)
Side effects : dizziness , drowsiness , GI upset , anxiety , arrhythmia, hypotension
Interacts with anything else that is a CNS depressant e.g. alcohol

Question 2

Flecainide (propafenone)

• Class
• mechanism
• What it’s used for
• side effects
• drug drug interactions

Answer 2

Uses : wide spectrum , supraventriuclar flutter, ectopic beats (premature ventricular arrhythmias) , Wolff-Parkinson-White syndrome (slows conduction through the pathway)
Side effects: pro-arrhythmia and sudden death (especially if used long term), CNS and GI effects
Class: 1C Na+ blocker
Mechanism: blocks Na+ channels slowing depolarisation no change to the effective refractory period

Question 3

Bisprolol

• Class
• Other drugs in the class
• mechanism
• What it’s used for
• side effects
• drug drug interactions

Answer 3

Type 2 antiarrythmic
Propranolol anything else ending in -o lol
Beta blockers
Mechanism: bind to B1 adrenergic receptors to block sympathetic action. This reduces catecholamines and reduces conduction through AV node. Reduces heart rate.
Uses: in supraventricular tachycardia e.g. AF
Side effects: AV node block, bronchospasm (so not in asthmatics) hypotension.

Question 4

Amiodarone

• Class
• mechanism
• What it’s used for
• side effects
• drug drug interactions

Answer 4

Class : type 3 antiarryhtmic K+ channel blocker
Mechanism: K+ channels blocked so slowed repolarisation and prolonged action potentials reduces heart excitability and stops reentrant tachycardia.
Uses: wide spectrum e.g. AF and VT
Side effects: Can get more likely with time. Pulmonary fibrosis Hepatic injury Increase LDL cholesterol Thyroid disease Photosensitivity optic neuritis (transient blindness)
Drug-drug interactions: reduce the dose of digoxin and monitor warfarin more closely

Question 5

Verapamil

Answer 5

Class 4: calcium channel blockers
Mechanism: Blocks calcium channels responsible for depolarisation through the AV and SA node. Reduce conduction through AV/SA and cardiac myocyte contractility.
Uses: control ventricles and prevents re-entry loops by blocking AV node during supraventricular tachycardia. Especially useful in asthmatics where can’t use Betablockers.
Side effects: Caution when partial AV block is present. Can get asystole
if β blocker is on board Caution when hypotension, decreased cardiac output. Some gastrointestinal problems (constipation). Don’t give with a calcium channel blockers unless they have a pacemaker.

Question 6

Digoxin

Answer 6

Class: 5 cardiac glycosides

Mechanism:blocks the Na+/K+ exchanger. This raises the intracelluar Na+ levels which stops the Ca2+/Na+ exchanger. This increases intracelluar Ca2+ which increases the force of contraction.
Also increases vagal stimulation which slows heart rate

Side effects: hyperkalaemia, arrhythmias, GI disturbance

Uses: increases Ca used to treat heart failure. reduces ventricular rates in AF and atrial flutter.

Drug-drug interactions: verapamil which exaggerates heart block, Amiodarone causes visual disturbances.