Transdermal penetrants vehicle

The lack of significant impact of CPEs on transdermal delivery vehicles is related to the inherent nonspecific activity of CPEs in the different strata of the skin, as discussed earlier. This limitation may be overcome by utilization of mixtures of CPEs. Research has already shown that binary mixtures of CPEs provide increased permeation enhancement as well as increased safety compared to single enhancers. Such unique chemical combinations, called synergistic combinations of penetration enhancers or SCOPE formulations, offer new opportunities in transdermal drug delivery (46). 

Sasaki, H., Kojima, M., Nakamura, J., and Shibasaki, J. (1990c). Einhancing effect of pyr-rolidone derivatives on transdermal penetration of phenolsulfonphthalein and indomethacin from aqueous vehicle, Chem. Pharm. Bull., 3S 191-199. 

Since transdermal penetration from microemulsion systems is likely to depend on the degree of perturbation of the layered structures of the stratum corneum and the generation of channels, it could be expected to depend on the microemulsion composition and structure (see above). For example, Osborne et al. [29] studied the transdermal penetration of glucose from W/O microemulsions prepared from octanol, dioctylsodium sulfosuccinate, and water and found that an increased microemulsion water content caused enhanced water penetration. Differences in percutaneous glucose transport were further shown to parallel differences in the diffusion of water within the microemulsion vehicles prior to application to the skin. 

Gwak H, Oh I, Chun I. Transdermal delivery of ondansetron hydrochloride effects of vehicles and penetration enhancers. Drug Dev Ind Pharm 2004 30 187-194. 

Surfactants—traditionally common constituents and stabilizers of topical vehicles, ranging from hydro-phobic agents such as oleic acid to hydrophilic sodium lauryl sulphate— have been tested as penetration enhancers to improve transdermal drug delivery. 

Lately, Cohen-Avrahami et al. used for the first time ceU penetrating peptides (CPPs) as enhancers to overcome the stratum corneum barrier [47]. Na-DFC is a common NSAID (non-steroid anti-inflammatory drug) used to treat mild to moderate pain, particularly when inflammation is also present. This study utilized the advantages of the Hu mesophase as a transdermal vehicle, in addition to those of the CPPs as skin penetration enhancers, for the development of improved drug delivery vehicles in which the dmg diffusion rate might be carefidly controlled. 

The applicability and efficiency of the Hn mesophase [43] and the corresponding hexosomes [76] as carriers for a transdermal delivery of desmopressin was also tested. In the case of bulk hexagonal mesophase, reduced values of steady-state flux of the drug and its permeability coefficients through the skin were obtained, and compared to water solution (Fig. 12.24). In other words, the peptide molecules penetrated more easily and freely through the skin from water solution than from hexagonal phase vehicles. Hence, a sustained release of desmopressin was obtained via the Hn mesophase. 

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