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Ketotifen pharmacokinetics in children with atopic perennial asthma
M L McFadyen1, R Miller, T M Ludden
1Pharmacology Department, University of Durban-Westville, South Africa. mcfadyen@pixie.udw.ac.za
Objective:
Published pharmacokinetic data on ketotifen are sparse, although it is a commonly used prophylactic agent in various allergic disorders in adults and children. The aim of this study was to assess the steady-state pharmacokinetics of ketotifen in children with atopic perennial asthma who were participating in a clinical trial.
Method:
The NONMEM population approach with sparse sampling was utilized. The data set consisted of 239 samples from 48 children who were randomized to receive either 1 mg or 2 mg oral ketotifen daily. Patients underwent a clinical examination and had a blood sample taken at 2-week intervals for 12 weeks. The ketotifen concentrations were measured by RIA.
Results:
A one-compartment model with first-order absorption was fit to the data. Volume was estimated at 394 l and clearance (CL) at 97.4 l.h-1 (3.6 l.h-1.kg-1). Weight or body surface area were the most influential covariates for explaining interindividual variability in CL. The 2-mg dose appeared to have a relative bio-availability of 85% of the 1-mg dose.
Conclusion:
Children have a faster clearance of ketotifen than adults and would therefore require a higher dose per kilogram body weight to give comparable steady-state levels.