title: Relation of serum reverse T3 to amiodarone antiarrhythmic efficacy and toxicity.
abstract: The relation of serum reverse T3 (rT3) to amiodarone efficacy and toxicity was studied in 31 patients with frequent and complex ventricular arrhythmias. Baseline studies included 48-hour Holter recordings and rT3 levels (normal 33 ng/dl or less). Amiodarone therapy was initiated with a 5 mg/kg infusion followed by 600 to 800 mg/day for 7 to 10 days, then 200 to 400 mg/day. Holters and rT3 levels were repeated every 1 to 3 months and amiodarone was titrated to achieve at least a 70% reduction in total ventricular premature complexes, at least a 90% reduction in couplets and abolition of ventricular tachycardia. The baseline rT3 level was 18 +/- 7 ng/dl (range 10 to 30) and patients were followed 12 +/- 9 months. Arrhythmia control was achieved in 25 patients (81%), including 21 patients with elevated rT3 levels (36 to 105 ng/dl) and 4 patients with normal rT3 (15 to 33 ng/dl). Six patients were uncontrolled with rT3 (27 to 90 ng/dl) and 14 patients had minor side effects with rT3 (27 to 123 ng/dl). Three of 4 patients in whom rT3 levels exceeded 130 ng/dl died suddenly (137 to 174 ng/dl before the event). Thus, amiodarone efficacy and minor toxicity occurs at rT3 levels less than 105 ng/dl and sudden death may be associated with levels greater than 130 ng/dl.
mesh_terms: D000368:Aged; D000638:Amiodarone / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D001572:Benzofurans / Q000627:therapeutic use*; D003327:Coronary Disease / Q000150:complications; D003645:Death, Sudden / Q000209:etiology; D004341:Drug Evaluation; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D013961:Thyroid Gland / Q000378:metabolism; D014285:Triiodothyronine, Reverse / Q000097:blood*; D014693:Ventricular Fibrillation / Q000188:drug therapy*
chemical_list: D001572:Benzofurans; D014285:Triiodothyronine, Reverse; D000638:Amiodarone