Salbutamol sulfate

Testosterone, testosterone-d₃ and fluorescein isothiocyanate dextran, average molecular weight 4000 Da (FD4) were purchased from Sigma Aldrich (Sigma Aldrich, Gillingham, UK) with ≥ 98% purity. Also purchased from Sigma Aldrich were HPLC-grade methanol. Ipratropium bromide monohydrate, tiotropium bromide monohydrate, budesonide and salbutamol sulfate were kindly supplied by GlaxoSmithKline, Stevenage, UK). Deionised water was used throughout.

A unit-dose of salbutamol sulfate (5.0 mg/2.5 mL, GlaxoSmithKline, Victoria, Australia) was diluted in 4 mL saline and was placed in a pneumatic-powered nebuliser (50 psi oxygen at the airflow rate of 8 L/min until 2 min after sputter sounded, Neb-Easy, Galemed Corp., Taipei, Taiwan). To reduce the percentage of drug dose remaining the medication cup, salbutamol was diluted before the nebulisation [15 (link)]. The nebuliser was connected to the manikin with either a facemask or a hood with three different inlet locations, with or without the front cover. The aerosolised drug was collected using a bacterial filter placed between the end of the trachea of the manikin and the breath simulator. Each nebulisation procedure was repeated five times.
The drug deposits on the collecting filter and drug remaining in the nebuliser (as residual dose) were eluted, and the drug on the face of the manikin was washed with 10 mL of distilled water for 3 min. The absorbance of each drug sample was measured using an ultraviolet spectrophotometer (Thermo Fisher Scientific Inc., Waltham, MA, USA) at a wavelength of 276 nm. There was a linear relationship between the absorption and concentration of salbutamol between 2.0 and 250 µg/mL with a slope of 0.0062 (R² = 0.9999). The salbutamol drug mass was then calculated from the absorption-concentration standard curve.