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Quinidine dosage in children using population estimates
Insights
Pediatric cardiac arrhythmia treatment with quinidine requires careful dosing adjustments. Dosing by body surface area is often excessive, while body weight dosing may be insufficient, necessitating individualized patient estimates for optimal therapeutic quinidine levels.
Area of Science:
- Pharmacology
- Pediatric Cardiology
- Clinical Pharmacy
Background:
- Cardiac arrhythmias in children require effective pharmacotherapy.
- Quinidine is an antiarrhythmic medication used in pediatric patients.
- Optimal dosing strategies for quinidine in children are not well-established.
Purpose of the Study:
- To identify factors influencing plasma quinidine concentrations in hospitalized pediatric patients.
- To develop patient population estimates for predicting effective quinidine dosages.
- To evaluate current dosing recommendations for quinidine in children.
Main Methods:
- Retrospective analysis of 36 plasma quinidine concentrations from nine pediatric patients.
- Stepwise multilinear regression to assess factors affecting plasma concentration.
- Comparison of quinidine dosing and plasma levels based on body weight and body surface area.
Main Results:
- Plasma quinidine concentration was significantly influenced by dose and time of blood draw, not patient age.
- Six of eight responders achieved normal sinus rhythm below 2.0 micrograms/ml.
- Concurrent digoxin use was associated with higher quinidine levels and shorter half-life.
Conclusions:
- Current quinidine dosing recommendations for children by body surface area are excessive.
- Dosing by body weight may be insufficient; individualized estimates are crucial.
- Patient population estimates aid in optimizing quinidine therapy for pediatric cardiac arrhythmias.
Abstract:
A total of 36 plasma quinidine concentrations from nine hospitalized pediatric patients with cardiac arrhythmias were examined retrospectively to determine factors significantly affecting quinidine dosing. Each plasma quinidine concentration was obtained after at least 24 h of inpatient therapy. Doses of quinidine base varied from 7.7 to 45.6 mg/kg/day and from 179 to 921 mg/m2/day. Six of the eight children who responded to quinidine achieved normal sinus rhythm with plasma concentrations less than 2.0 micrograms/ml. Stepwise multilinear regression analysis demonstrated that the plasma concentration was significantly affected by the quinidine dose and by the time after the dose that the plasma was obtained, but not by the age of the patient. Patient population estimates were then derived to predict the quinidine dosage necessary to achieve given plasma concentrations. The group of patients receiving digoxin concurrently were predicted to obtain higher plasma quinidine levels on smaller doses and a shorter quinidine elimination half-life compared with those patients not on digoxin. While currently recommended quinidine doses by body weight are frequently insufficient, recommended quinidine doses by body surface area are excessive. Children require larger quinidine doses on a body weight basis and respond to a wide range of plasma quinidine concentration. Patient population estimates provide useful information on dosing of infrequently prescribed drugs in children.