[Plasma concentrations and amiodarone/desethylamiodarone relations in patients subjected to chronic treatment]

We measured plasma concentrations of amiodarone and desethylamiodarone by HPLC in 44 outpatients aged 24 to 67 years old (21 male), receiving the drug during at least three months. The drug was indicated for supraventricular arrhythmias in 37 patients and ventricular arrhythmias in seven. Plasma concentrations of amiodarone, desethylamiodarone and their ratio were 1.71 +/- 0.82, 0.85 +/- 0.42 micrograms/ml and 2.02 respectively, for a mean daily dose of 223 +/- 88 mg. In 41 patients, arrhytmias were successfully treated. These patients received a mean daily dose of 220 +/- 86 mg and concentrations of amiodarone, desethylamiodarone and their ratio were 1.75 +/- 0.86, 0.88 +/- 0.45 micrograms/ml and 1.99 respectively. In three patients with treatment failure, receiving a daily dose of 257 +/- 115 mg, these figures were 1.2 +/- 0.3, 0.5 +/- 0.1 micrograms/ml and 2.4 respectively. We conclude that our patients had lower plasma concentrations of desethylamiodarone and higher amiodarone/desethylamiodarone ratios than those reported in other countries.