[Monitoring amiodarone].

Area of Science:

• Pharmacology
• Clinical Chemistry

Context:

• Amiodarone is an antiarrhythmic drug with complex pharmacokinetics.
• Monitoring serum drug concentrations is crucial for optimizing therapy and minimizing toxicity.

Purpose:

• To determine serum amiodarone (A) and desethylamiodarone (D) levels in adults and children receiving amiodarone.
• To investigate the relationship between dosing regimens and serum drug concentrations.
• To identify potential correlations between serum levels and toxicity.

Summary:

• Serum amiodarone (A) and desethylamiodarone (D) levels were measured using HPLC in 34 adults on loading or maintenance amiodarone therapy.
• Intravenous loading doses resulted in significantly higher serum A levels (1.35 µg/mL) compared to oral doses (0.51 µg/mL), indicating lower oral bioavailability.
• During maintenance therapy, serum A levels were low initially (0.31 µg/mL) but increased over 3 months (0.53 µg/mL), with a rising D/A ratio.
• One of four pediatric patients on maintenance therapy exhibited high serum A (1.50 µg/mL) and D (2.50 µg/mL) levels, accompanied by nervous and cutaneous toxicity.

Impact:

• Findings suggest variability in amiodarone bioavailability and highlight the importance of therapeutic drug monitoring.
• The study identifies potential pharmacokinetic changes during maintenance therapy and in pediatric populations.
• Results underscore the need for careful dose titration and toxicity assessment in patients receiving amiodarone.