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Saturday 01 December 2001

An investigation of in vitro/in vivo correlations for salbutamol nebulized by eight systems.

By: Silkstone VL, Dennis JH, Pieron CA, Chrystyn H.

J Aerosol Med 2002 Fall;15(3):251-9

The choice of a nebulized system for a patient usually depends on the equipment available. To date, there is limited guidance on the selection and use of a nebulizer. We have conducted in vitro tests described within the draft European Standard for Nebulisers (BSEN13544-1; CEN) and correlated these to in vivo pharmacokinetic performance of relative lung and systemic deposition in healthy volunteers. Eight nebulizer systems have been tested. The in vitro analysis used the recommended CEN methods to quantify the total dose available for inhalation as well as the size distribution from which the respirable dose was determined. The draft European Standard methods were slightly modified to use salbutamol rather than a fluoride tracer. For the in vivo study, nine volunteers provided urine samples after 30 min and then pooled for 24 h after the start of each nebulized dose (2.5 mg of salbutamol). Amounts of salbutamol and its metabolite excreted in the urine samples were determined. There was a significant (p = 0.02) correlation between the in vitro respirable dose and the amount of salbutamol excreted in the urine 30 min after the start of nebulization (relative bioavailability of salbutamol to the lung). Also, there was a significant (p < 0.001) correlation between the in vitro dose available for inhalation and the total amount of salbutamol and its metabolites excreted over the 24 h after the start of nebulization (relative bioavailability of salbutamol to the body). The results demonstrate that in vivo/in vitro correlations exist and warrant further investigations. The in vitro methods require further validation with in vivo correlations using patients with different severities of airway obstruction.

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