Systemic Bioavailability and Potency of High-Dose Inhaled Corticosteroids: Protocol
High doses of drugs were used to magnify the differences between them. Two milligrams of fluticasone and budesonide was used to assess the effects of doses that might be used in clinical practice and to study the dose-response relationship. Drugs were taken in random order at least 7 days apart. All subjects were instructed in the correct usage of the devices and their techniques were checked. Single deep inhalations from the device were followed by 10 s of breath-holding with a minimum interval of 30 s before the next dose. To minimize deposition on the spacer, only one puff of drug was delivered into the spacer at one time. Each spacer was primed with 20 puffs of drug prior to every drug administration in order to prevent drug adhering to the wall of the spacer due to the electrostatic attraction that occurs in new plastic spacer devices. Spacer devices were washed with water after use and allowed to dry naturally. A bank of three Nebuhaler devices and three Volumatic devices were used to deliver all treatments. All six devices were subjected to a similar amount of usage and washing during the course of the study. The aerosol canister and plastic actuators were masked to blind the treatment to the subjects and investigators. All aerosol containers had their labels removed and replaced with a code letter, and all MDI treatments were taken through the white “placebo” actuator supplied by the manufacturer of each drug. The chief investigator kept a record of all treatments and codes. Nebulized and oral budesonide were administered in an open manner as no suitable placebo was available. A single nebulizer was used throughout the study. anti allergy
Ten milliliters of venous blood was drawn between 8:30 and 9:30 am on the morning following each treatment. If a subject attended later than 9:30 am, the test was repeated 1 week later. Cortisol levels were measured using an in-house radioimmunoassay using cortisol antiserum from the Scottish Antibody Production Unit and a I cortisol derivative as label. Separation of the antibody bound and free fractions was accomplished with second antibody-coated cellulose. Standards were prepared in hormone-free human serum. The reference range for cortisol using this assay is 250 to 650 nmol/L at 9:00 am.