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Pharmacology: Pharmacokinetics: In a pharmacokinetic study, the estimated daily infant dose was 0.3% of the daily maternal dose for both dose levels, and the average plasma concentration in infants was estimated lobe 1/600.
In adults the systemic bioavailability of budesonide following administration of Budesonide Suspension for Nebulization via a jet nebulizer is approximately 15% of the declared dose and 40-70% of the dose delivered to the patient. A small part of the systematically available dose comes from inhalation suspension that is allowed. The peak plasma concentration following administration of a single dose of 2 mg is achieved 10 -30 minutes after the beginning of inhalation and is approximately 4 nmol/L. In children (4 - 6 years), the systemic bioavailability of budesonide after administration of Budesonide Suspension for Nebulization via jet nebulizer is approximately 6% of the declared dose and 26% of the dose administered to the patient. The peak plasma concentration following administration of a single dose of 1 mg Is approximately 20 minutes after the beginning of inhalation and is approximately 2.4 nmol/L.
Distribution: The volume of distribution in adults is approximately 3 L/kg. Plasma protein binding is approximately 85-90%.
Metabolism: Budesonide undergoes extensive, (90%) first pass biotransformation in the liver via CYP3A4 to metabolites with a low glucocorticosteroid activity. The in-vitro activity of the main metabolites, 6,α-hydroxyprednisolone, and 16-α-hydroxyprednisolone, is less than 1% of that budesonide.
Excretion: The metabolites are excreted in unchanged or conjugated form predominantly via the kidneys.
No unchanged budesonide is found in the urine. Budesonide has a high systemic clearance (approximately 1.2 Liters/min) in healthy adults, and the elimination half-life following intravenous administration is approximately 2-3 hours. Budesonide has a systemic clearance of approximately 0.5 L/min in 4 to 6 year old asthmatic children.
Children have an approximately 50% higher clearance per kg body weight than adults. The half-life of budesonide following inhalation is about 2.3 hours in asthmatic children, which is roughly the same in healthy adults.
