[Monitoring amiodarone]

Serum levels of amiodarone (A) and desethylamiodarone (D) were determined by HPLC in 34 adults receiving loading (2 g) or maintenance doses (200 mg daily) of amiodarone. Serum levels of A after i.v. loading doses were much higher (1.35 micrograms/ml) than after equivalent oral doses (0.51 microgram/ml), suggesting low bioavailability. During maintenance therapy, very low levels of A were measured during the first 3 months of treatment (0.31 microgram/ml), after which they tended to rise (0.53 microgram/ml), as did the ratio of D/A. Among 4 children under maintenance therapy, one had high serum levels of A (1.50 micrograms/ml) and D (2.50 micrograms/ml) and showed nervous and cutaneous signs of toxicity.