Anti - dysrhythmics Flashcards
Anti - Dysrhythmics
Amiodarone
How do Anti-Dysrhythmics work?
Amiodarone has many effects on myocardial cells, including blockade of sodium, calcium and potassium channels, and antagonism of α- and β-adrenergic receptors. These effects reduce spontaneous depolarisation (automaticity), slow conduction velocity, and increase resistance to depolarisation (refractoriness), including in the atrioventricular (AV) node. By interfering with AV node conduction, amiodarone reduces the ventricular rate in AF and atrial flutter. Through its other effects, it may also increase the chance of conversion to, and maintenance of, sinus rhythm. In SVT involving a self-perpetuating (‘re-entry’) circuit that includes the AV node, amiodarone may break the circuit and restore sinus rhythm. Amiodarone’s effects in suppressing spontaneous depolarisations make it an option for both treatment and prevention of VT. The same rationale underlies its use in refractory VF, although there is little evidence from clinical trials to support this.
Indications of Anti - Dysrhythmics
In the management of a wide range of tachyarrhythmias, including atrial fibrillation (AF), atrial flutter, supraventricular tachycardia (SVT), ventricular tachycardia (VT) and refractory ventricular fibrillation (VF). It is generally used only when other therapeutic options (drugs or electrical cardioversion) are ineffective or inappropriate.
Contraindications of Anti - Dysrhythmics
Amiodarone is a potentially dangerous drug that should be used only when the risk–benefit balance justifies this. It should specifically be avoided in patients with severe hypotension, heart block and active thyroid disease.
Side effects of Anti - Dysrhythmics
In acute use, compared with other antiarrhythmic drugs, amiodarone causes relatively little myocardial depression, although it can cause hypotension during IV infusion. When taken chronically, it has many side effects, a number of which are serious. These include effects on the lungs (pneumonitis), heart (bradycardia, AV block), liver (hepatitis) and skin (photosensitivity and grey discolouration). Due to its iodine content (amIODarone) and structural similarities to thyroid hormone, it may cause thyroid abnormalities, including hypo- and hyperthyroidism. Amiodarone has an extremely long half-life. After discontinuation, it may take months to be completely eliminated.
Interactions of Anti - Dysrhythmics
Amiodarone interacts with many drugs – too many to list here. Notably, it increases plasma concentrations of digoxin, diltiazem and verapamil. This may increase the risk of bradycardia, AV block and heart failure. The doses of these drugs should be halved if amiodarone is started.
Elimination of Anti - Dysrhythmics
Hepatic
Patient information on Anti - Dysrhythmics
In cardiac arrest, amiodarone is given as a bolus injection.
explain that you are advising treatment aimed at correcting their fast or irregular heart rhythm.
In long-term use, ask the patient to report any symptoms of breathlessness, persistent cough, jaundice, restlessness, weight loss, tiredness or weight gain.
Advise the patient not to drink grapefruit juice, as this can increase the risk of side effects, and to avoid exposure of their skin to direct sunlight due to the risk of photosensitivity.
