[Control of anti-arrhythmia therapy with amiodarone. Value of the determination of blood levels].

An antiarrhythmic treatment was done in 56 patients with recurrent ventricular tachycardias using amiodarone. The dosage was 400 to 600 mg/d following a loading dosage of 1000 mg for 8 to 12 days. Amiodarone and desethylamiodarone concentration in serum (control group n = 33) and in erythrocyte haemolysate (control group n = 13) were determined in relapses of ventricular tachycardias (n = 7) and in pulmonary fibrosis as serious side effect (n = 3). It was shown that amiodarone levels rise continuously during loading treatment until the 8th to 12th day and that desethylamiodarone can be demonstrated after the 3rd day of treatment. The mean concentrations (+/- standard deviation) of amiodarone and desethylamiodarone were 2.21 +/- 0.89 microgram/ml and 1.3 +/- 0.74 microgram/ml in serum and 0.97 +/- 0.65 microgram/ml and 1.95 +/- 1.9 micrograms/ml in erythrocyte haemolysate. Amiodarone levels did not correlate with efficacy and with incidence of side effects. However, in pulmonary fibrosis high desethylamiodarone concentrations in serum (greater than 2.5 micrograms/ml) and in erythrocyte haemolysate (greater than 4 micrograms/ml) were found. Four out of 7 patients with recurrent ventricular tachycardia showed relatively low desethylamiodarone concentrations in serum (desethylamiodarone/amiodarone ratio less than 0.4). Thus control of amiodarone treatment can be enlarged by determination of desethylamiodarone levels as its concentrations correlate with relapses of ventricular tachycardias and serious side effects.