A microcalorimetric study of surfactant aggregation and surfactant-drug interaction in a model inhalation aerosol system

Blackett, P.M. and Buckton, G. (1995) A microcalorimetric study of surfactant aggregation and surfactant-drug interaction in a model inhalation aerosol system. International Journal of Pharmaceutics, 125 (1). pp. 133-139. 10.1016/0378-5173(95)00132-3.

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DOI: 10.1016/0378-5173(95)00132-3


Two surfactants, oleic acid and Span 85, have been diluted from concentrated solution in Arcton 113 by gradual titration into Arcton 113 in a titration cell of an isothermal microcalorimeter. The heat of dilution responses revealed areas of interest in which it can be assumed that the state of aggregation of the surfactants changes. These points are at concentrations of approx. 0.3 and 0.7% w/v for oleic acid and at 0.8% w/v for Span 85. The experiments were repeated with salbutamol base suspended in Arcton 113, such that the adsorption of surfactant to the drug could be investigated. For both surfactants the results when drug was present were significantly different from those when drug was absent (dilution only). For oleic acid the data with drug were more exothermic and for Span 85 they were more endothermic, indicating different thermodynamics of adsorption for the two surfactants. For both surfactants there were break points in the adsorption data at concentrations corresponding to the break points in the dilution data. It can be concluded that the adsorption process is highly dependent upon the structure of surfactant in solution. For both surfactants the critical concentration was at or just below the value of 1% that has been found to be an effective surfactant loading for the production of inhalation aerosols. This data provides an explanation for the practical observation on surfactant use and demonstrates that microcalorimetry is a valuable technique for studies on these difficult systems.

Item Type:Article
Uncontrolled Keywords:Isothermal microcalorimetry; Salbutamol; Metered dose inhaler; Adsorption; Oleic acid; Span 85; Critical micelle concentration
Departments, units and centres:Department of Pharmaceutics > Department of Pharmaceutics
ID Code:3264
Journal or Publication Title:International Journal of Pharmaceutics
Deposited By:Library Staff
Deposited On:18 May 2012 11:46
Last Modified:18 May 2012 11:46

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