Amiodarone and thyroid status in refractory arrhythmias.
Out of 20 subjects selected for refractory arrhythmias, amiodarone therapy (200 mg/day) was efficacious in 85%. No statistically significant variations in electrocardiographic parameters (QTc) were observed; similarly, there was little evidence of side effects 1 year after initiation of treatment. These results were most likely due to the low daily dosage administered. We observed: 1) a significant increase in rT3 levels; 2) a decrease in TT3; 3) a uniform homeostasis of free fraction (FT3;FT4) These effects are all characteristic patterns of a "Low T3 Syndrome". The dosage of circulating amiodarone in 6 patients with borderline hormonal status (3 hyper- and 3 hypothyroidism) was not found to be an efficacious test for therapeutic monitoring. Identification of a statistically significant linear regression relationship between cumulative dose of amiodarone and rT3 levels may be a useful test in clinical practise for establishing more appropriate therapeutic dosages. Furthermore, it provides a guideline for threshold levels (maximum rT3 = 100-110 ng/dl) which are in close association with several side effects.
Piffanelli
A
A
Istituto di Radiologia, Universita' degli Studi Ferrara, Italy.
Pelizzola
D
D
Ricci
L
L
Codecà
L
L
Giovannini
G
G
Giganti
M
M
Colamussi
V
V
D000328:Adult; D000368:Aged; D000638:Amiodarone / Q000009:adverse effects / Q000097:blood / Q000627:therapeutic use*; D001145:Arrhythmias, Cardiac / Q000097:blood / Q000188:drug therapy*; D004305:Dose-Response Relationship, Drug; D004341:Drug Evaluation; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013961:Thyroid Gland / Q000187:drug effects*; D013974:Thyroxine / Q000097:blood; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood
D014284:Triiodothyronine; D000638:Amiodarone; D013974:Thyroxine