Systemic availability and pharmacokinetics of nebulised budesonide in preschool children

AIM—To evaluate thesystemic availability and basic pharmacokinetic parameters ofbudesonide after nebulisation and intravenous administration inpreschool children with chronic asthma.
METHODS—Plasmaconcentrations of budesonide were measured for three hours after anintravenous infusion of 125 µg budesonide. The children then inhaleda nominal dose of 1 mg budesonide through the mouthpiece of a Pari LCJet Plus nebuliser connected to a Pari Master compressor, and theplasma concentrations of budesonide were measured for another sixhours. The amount of budesonide inhaled by the patient ("dose tosubject") was determined by subtracting from the amount of budesonideput into the nebuliser, the amount remaining in the nebuliser afternebulisation, the amount emitted to the ambient air (filter), and theamount found in the mouth rinsing water.
RESULTS—Ten patientsaged 3 to 6 years completed both the intravenous and the inhaledtreatment. The mean dose to subject was 23% of the nominal dose. Thesystemic availability of budesonide was estimated to be 6.1% of thenominal dose (95% confidence intervals (CI), 4.6% to 8.1%) or 26.3%of the dose to subject (95% CI, 20.3% to 34.1%). Budesonideclearance was 0.54 l/min (95% CI, 0.46 to 0.62), steady state volumeof distribution 55 litres (95% CI, 45 to 68), and the terminal halflife was 2.3 hours (95% CI, 2.0to 2.6).
CONCLUSIONS—Approximately6% of the nominal dose (26% of the dose to subject) reached thesystemic circulation of young children after inhalation of nebulisedbudesonide. This is about half the systemic availability found inhealthy adults using the same nebuliser.