Steroidici

Unguentele si gelurile sunt mai penetrante decat cremele si lotiunile. Exista insa creme cu potenta comparabila cu a unor preparate ocluzive. Solutiile pot fi folosite ca excipient avand si un efect de racorire si uscare. Sunt de preferat la nivelul pielii paroase si al leziunilor exudative. Gelurile determina o penetrabilitate mai mare decat solutiile si pot fi folosite deasemenea la nivelul zonelor acoperite de par. Cremele sunt deasemenea folosite ca excipient pentru glucocorticoizi: cele ulei in apa au rol de uscare si racorire in timp ce cremele apa in ulei, avand mai putina apa, sunt mai emoliente.

A steroid ester is an ester of a steroid . [1] [2] They include androgen esters , estrogen esters , progestogen esters , and corticosteroid esters . [1] Steroid esters may be naturally occurring / endogenous like DHEA sulfate or synthetic like estradiol valerate . [1] [2] Esterification is useful because it is often able to render the parent steroid into a prodrug of itself with altered chemical properties such as improved metabolic stability , water solubility , and/or lipophilicity . [2] This, in turn, can enhance pharmacokinetics , for instance by improving the steroid's bioavailability and/or conferring depot activity and hence an extended duration with intramuscular or subcutaneous injection . [1] [3]

Steroid isolation , depending on context, is the isolation of chemical matter required for chemical structure elucidation, derivitzation or degradation chemistry, biological testing, and other research needs (generally milligrams to grams, but often more [37] or the isolation of "analytical quantities" of the substance of interest (where the focus is on identifying and quantifying the substance (for example, in biological tissue or fluid). The amount isolated depends on the analytical method, but is generally less than one microgram. [38] [ page needed ] The methods of isolation to achieve the two scales of product are distinct, but include extraction , precipitation, adsorption , chromatography , and crystallization . In both cases, the isolated substance is purified to chemical homogeneity; combined separation and analytical methods, such as LC-MS , are chosen to be "orthogonal"—achieving their separations based on distinct modes of interaction between substance and isolating matrix—to detect a single species in the pure sample. Structure determination refers to the methods to determine the chemical structure of an isolated pure steroid, using an evolving array of chemical and physical methods which have included NMR and small-molecule crystallography . [2] :10–19 Methods of analysis overlap both of the above areas, emphasizing analytical methods to determining if a steroid is present in a mixture and determining its quantity. [38]

Steroidici

steroidici

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