amiodarone
amiodarone
introduction:
-
commonly used in Rx of many arrhythmias including
VT,
AF
actions
primarily a class III antiarrhythmic agent but also:
sodium channel blockade (class I activity)
mild beta blocking action (class II activity)
some calcium channel blockade (class IV activity)
directly decreases sinus node and junctional automaticity
slows atrioventricular (AV) conduction
slows abnormal bypass tract conduction
prolongs refractory period of myocardial tissues (atria, ventricles, AV node and bypass tracts)
but does not significantly depress the spontaneous diastolic depolarisation of Purkinje fibres
prolonged QRS and QTc
may cause U waves and changed T waves on ECG
strong anti-fibrillatory action
increases coronary blood flow
reduces myocardial oxygen consumption without altering cardiac output
antagonistic to catecholamines and sympathomimetic agents without causing ß-adrenergic blockade
C/I
cardiac conduction blocks unless functioning pacemaker in situ
bradycardia
hypotension
lactation
pregnancy - class C drug
care with use of other cardiac drugs such as digoxin, anti-arrhythmics
PH thyroid disorders is a precaution for ongoing Rx
dose and usage:
IV acute dosage:
IV maintenance dosing:
oral dosing
load dose 200-400mg tds for 1wk, then
200-400mg bd for 1wk, then
100-200mg daily
acute adverse effects include:
hypotension
symptomatic bradycardias
-
adverse effects of long term maintenance dosing:
common & increase markedly after 1st yr of use when 75% will have adverse effects!
symptomatic pulmonary toxicity in 10-15% > 1yr use → death in 10% of those affected
hepatic injury common but rarely fatal
aggravation of arrhythmia in 2-5% pts
asymptomatic corneal microdeposits in all
cutaneous photosensitivity 10-15%
blue discoloration 5%
symptomatic hypothyroidism 5% & hyperthyroidism 2% (inhib. periph. T4 → T3);
NB. each amiodarone 200 mg tablet contains organic iodine approximately 75 mg and, in the steady state, metabolism of amiodarone 300 mg yields iodine 9 mg/day, well in excess of the highest normal dietary intake
substantial increased LDL-cholesterol occurs frequently
some drug interactions:
amiodarone.txt · Last modified: 2015/12/31 14:19 (external edit)