normal or elevated in Type 1 hyperthyroidism but is very low or
absent in Type 2 hyperthyroidism. Interleukin-6 levels are normal
or moderately increased in Type 1, but markedly increased in Type
2 amiodarone-induced hyperthyroidism. In addition, colour flow
Doppler ultrasound shows an absence of vascularity in Type 2
amiodarone-induced hyperthyroidism.
Amiodarone-induced hypothyroidism is characterised by an
elevated TSH. Treatment of amiodarone-induced hypothyroidism
is indicated if the free T4 is low or low normal and the TSH is
greater than 20 microIU/ml.
As a complication of therapy, hyperthyroidism is more
common where dietary iodine intake is low, whilst the reverse is
true in areas of high intake.^4 In patients with hyperthyroidism in
whom amiodarone therapy is still warranted, thought should be
given to concomitant treatment with carbimazole.^5
TTaabbllee 8855 .. 11 IInncciiddeennccee ((%% aanndd ooddddss rraattiiooss)) ooff aaddvveerrssee rreeaaccttiioonnss iinn ttwwoo
rreecceennttllyy ppuubblliisshheedd mmeettaa--aannaallyysseess
AATTMMII** mmeettaa--aannaallyyssiiss^11 LLooww--ddoossee mmeettaa--aannaallyyssiiss^22
AAmmiioo-- PPllaacceebboo OORR†† AAmmiioo-- PPllaacceebboo OORR
ddaarroonnee ddaarroonneePulmonary 1.6 0.5 3.1 1.9 0.7 2.2
Hepatic 1.0 0.4 2.7 1.2 0.8 1.2
Thyroid 8.4 1.6 4.9 3.7 0.4 4.2
Bradycardia 2.4 0.8 2.6 3.3 1.4 2.2
Neurologic 0.5 0.2 2.8 4.6 1.9 2.0
Skin NR‡ NR NR 2.3 0.7 2.5
Eye NR NR NR 1.5 0.1 3.4
Gastrointestinal NR NR NR 4.2 3.3 1.1
Drug
Discontinuation 41 27 NR 23 15 NR
*ATMI = Amiodarone Trials Meta-Analysis Investigators; † OR = odds ratio;
‡ NR = not reported
RReeffeerreenncceess
1 Amiodarone Trials Meta-Analysis Investigators. Effect of prophylactic
amiodarone on mortality after acute myocardial infarction and in
congestive heart failure: meta-analysis of individual data from 6500
patients in randomized trials. Lancet1997; 335500 : 1417–24.
2 Vorperian VR, Harighurst TC, Miller S et al. Adverse effects of low dose
amiodarone: a meta-analysis. J Am Coll Cardiol1997; 3300 : 791–8.
3 Gleadhill IC, Wise RA, Schonfeld S et al. Serial lung function testing in
patients treated with amiodarone: a prospective study. Am J Med 1989
; 8866 : 4–10.