PHARMACOKINETICS AND PHARMACODYNAMICS OF INHALED CORTICOSTEROIDS

There are significant differences in the pharmacokinetic properties of inhaled corticosteroids currently used in medical practice. All are r apidly cleared from the body but they show varying levels of oral bioa vailability and more importantly variation in the rate of absorption a fter inhalation. Oral bioavailability is lowest for fluticasone propio nate, indicating a low potential for unwanted systemic corticosteroid effects. Mathematical modeling has shown pulmonary residence times to be longest for fluticasone propionate and triamcinolone acetonide but shortest for budesonide and flunisolide. These properties appear to re late to pulmonary solubility, which appears to be the rate-limiting st ep in the absorption process.