Detection and pharmacokinetics of salbutamol in thoroughbred racehorses following inhaled administration

Salbutamol sulphate (Ventolin Evohaler) was administrated via the inhalation route to six horses at a dose of 0.5 mg every 4 h during the day for 2 days (total dose 4 mg). Urine and blood samples were taken up to 92 h postadministration. Hydrolyzed plasma and urine were extracted using solid phase extraction (SPE). A sensitive tandem mass spectrometric method was developed in this study, achieving a lower limit of quantification (LLOQ) for salbutamol of 10 pg/mL in plasma and urine. The parent drug was identified using UPLC‐MS/MS. Most of the determined salbutamol plasma concentrations, post last administration, lie below the LLOQ of the method and so cannot be used for plasma PK analysis. Urine PK analysis suggests a half‐life consistent with the pharmacological effect duration. An estimate of the urine average concentration at steady‐state was collected by averaging the concentration measurements in the dosing period from −12 to 0 h relative to the last administered dose. The value was averaged across the six horses and used to estimate an effective urine concentration as a marker of effective lung concentration. The value estimated was 9.6 ng/mL and from this a number of detection times were calculated using a range of safety factors.
Source: Journal of Veterinary Pharmacology and Therapeutics - Category: Veterinary Research Authors: Tags: Scientific Paper Source Type: research