The Bioavailability of Salbutamol in Urine via Volumatic and Nonvolumatic Valved Holding Chambers.

PURPOSE: Pressurized metered dose inhalers are commonly used in patients with asthma. However, the need to coordinate inhalation with inhaler actuation means that they are not suitable for use per se. Valved holding chamber devices were developed to overcome some of the problems of pressurized metered dose inhalers. Several types of holding chambers of different sizes are available in Iran. This study was designed to compare the effects of 2 commonly used valved holding chambers (Asthm Yar and Dam Yar) in Iran on bioavailability of salbutamol spray and also spirometric parameters in asthmatic patients.

METHODS: This was a comparative experimental crossover study. Patients with mild to moderate asthma were entered in this study. Lung function was assessed using a portable spirometer (Spirolab, Progetti, Italy). Spirometric parameters of forced expiratory flow (FEF)(50%), FEF(25-75%), peak expiratory flow (PEF), forced expiratory volume in the first second of expiration (FEV(1)), forced vital capacity (FVC), and FEV(1)/FVC were measured. Urinary concentration of salbutamol as an index of pulmonary bioavailability was assayed with high-performance liquid chromatography.

RESULTS: Forty patients (25 women and 15 men) with the mean age of 43.10 ± 12.99 years were studied. Mean ± SD changes of spirometric parameters before and after using Asthm Yar were not significantly different from those of Dam Yar. The relative bioavailability after inhalation with Asthm Yar was significantly higher than after inhalation with Dam Yar (P = 0.002).

CONCLUSIONS: Although the results indicate that relative bioavailability to the lung after inhalation with Asthm Yar was significantly higher than after inhalation with Dam Yar, its clinical importance should be tested.