Acetic acid Betamethasone dipropionate

Aerosols used for inhalation therapy are generally packaged in containers with metered values. The standard procedure is to discharge the entire contents of the container for assay. For betamethasone dipropionate and betamethasone valerate topical aerosols, the contents are discharged into a volumetric flask and the propellants carefully boiled off. Precautions should be taken, as many of these propellants are flammable. The residue is diluted to volume with isopropanol-acetic acid (1000 1) and filtered [50]. Another approach is to discharge the contents into ethanol or dilute acid. An alternative is to immerse the canister in liquid nitrogen for 20 min, open the canister, evaporate the liquid contents, and dissolve the residue in dichloromethane. A unit spray sampling apparatus for pressurized metered inhalers has been described [51]. The components in an aerosol product that can be the cause of assay variance have been studied [52]. A method to quantify the volatile components of aerosol products has been developed [53]. 

Marini, R.D. PanteUa, A. Bimazubute, M A. Chiap, P. Hubert, P. Crommen, J. Optimisation and validation of a generic method for the LC assay of six corticosteroids and salicylic acid in der-mopharmaoeutical forms, Chromatographia, 2002, 55, 263-269. [saUcylic acid methyl paraben propyl paraben triamcinolone acetonide hydrocortisone acetate betamethasone valerate clobetasol propionate clobetasone butyrate betamethasone dipropionate]... 

In order to increase their Upid solubility, corticosteroids have been esterified with monocarboxylic (fatty) acids. Examples include hydrocortisone acetate, beclomethasone dipropionate and betamethasone isovalerate. For triamcinolone, the following method has been developed to make the substance lipophilic the hydroxyl groups at the C16 and C17-position of triamcinolone are used to form a cyclic acetal (Fig. 18.4). Although the formed substance, triamcinolone acetonide, is not a fatty acid ester, with regard to lipid solubility it behaves as such. 

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