Amiodarone/N-desethylamiodarone population pharmacokinetics in pediatric patients

Amiodarone extraction by continuous renal replacement therapy: results from an ex vivo study

Continuous renal replacement therapy (CRRT) is a lifesaving therapy for critically ill patients with acute renal failure. Some patients supported with CRRT suffer from cardiac arrhythmias, which are often treated with amiodarone. While amiodarone is a very effective antiarrhythmic, it has a relatively narrow therapeutic window and a long half-life, making it challenging to dose safely. This is especially true in patients supported with CRRT, where drug pharmacokinetics are likely altered. This ex vivo study measured the extent of amiodarone extraction by the CRRT circuit. Amiodarone was administered to a closed-loop CRRT circuit. Drug was dosed to achieve therapeutic concentrations. Circuits were primed with a human blood-plasma mixture and maintained at physiologic temperature and pH. Serial blood samples were collected over time and drug concentrations were quantified. Amiodarone was heavily extracted by the ex vivo CRRT circuit with only 23% amiodarone remaining in the plasma at 6 h. The relative concentration was significantly greater in the controls than in the CRRT circuits within 2 h (n = 3; p = 0.0059). Amiodarone is heavily adsorbed by CRRT circuit components, suggesting that clinical dosing adjustments are likely required to achieve therapeutic targets.

Impact of Body Mass Index in the Cardioverter Efficacy of Amiodarone in Persistent Atrial Fibrillation

BACKGROUND

Amiodarone is an anti-arrhythmic drug that has extensive tissue distribution and substantial storage in the fat tissue. Different studies have described some implications of body fat composition in its pharmacokinetics and pharmacodynamics. However, no clinical studies have described its implications for clinical efficacy.

METHODS

We studied 878 patients with persistent atrial fibrillation (AF) treated with a regimen of amiodarone and referred to electrical cardioversion (ECV), included prospectively in two Spanish registries. We analyzed the influence of body mass index (BMI), as well as overweight and obesity, in the efficacy of amiodarone for achieving pharmacologic cardioversion to sinus rhythm (SR) before ECV.

RESULTS

A total of 185 patients (21.1%) reverted to SR before ECV. Patients who reverted to SR had a lower BMI than those who did not revert (27.45 ± 4.36 kg/m2 vs. 29.11 ± 4.09 kg/m2; p < 0.001). We observed a progressively lower probability of reverting to SR in overweight and obese patients (normal weight 28.3%, overweight 21.3%, obesity 13.1%; p < 0.001). In the logistic regression, BMI (kg/m2) adjusted for other related variables remained as the main factor inversely related to reversion to SR (OR = 0.904 × kg/m2); CI 75% 0.864-0.946).

CONCLUSIONS

We observed a negative relationship between an increased BMI and the efficacy of amiodarone for reversion to SR, suggesting a negative clinical impact of excess body fat in its efficacy.

Pediatric antiarrhythmics and toxicity: A clinical review

Antiarrhythmic medications are fundamental in the acute and chronic management of pediatric arrhythmias. Particularly in the pediatric patient population, associated antiarrhythmic toxicities represent important potential adverse effects. Emergency medicine clinicians must be skilled in the detection, workup, and management of antiarrhythmic toxicity. This is a clinical review of the indications, pharmacology, adverse effects, and toxicologic treatment of antiarrhythmics commonly used in the pediatric patient population.