Drug permeation rate

Drugs Permeation Rate Treatment Daily Dose2 TDD Size... 

Hammer and coworkers prepared PEG-h-PCL polymersomes entrapping DXR (Fig. 11a). The release of DXR from the polymersomes was in a sustained manner over 14 days at 37 °C in PBS via drug permeation through the PCL membrane, and hydrolytic degradation of the PCL membrane [228]. The release rate of encapsulated molecules from polymersomes can be tuned by blending with another type of block copolymer [229]. Indeed, the release rate of encapsulated DXR from polymersomes prepared from mixtures of PEG- -PLA with PEG- -PBD copolymers increased linearly with the molar ratio of PEG- -PLA in acidic media (Fig. lib). Under acidic conditions, the PLA first underwent hydrolysis and, hours later, pores formed in the membrane followed by final membrane... 

Mucus also appears to be a barrier to the permeation enhancing effect of polymeric or monomeric absorption enhancers. In the above mentioned TMC studies, the enhancement effect (enhancement ratio = permeation rate of the drug in the presence... 

The lag time evident in the dissolution profile of the second dose is determined by the progressive gelation of the intermediate barrier in addition, since the dissolution medium permeates the barrier very slowly and wets the third layer, the disintegrant efficiency could be reduced, thus resulting in a significant decrease of drug dissolution rate. 

However, some negative effects of the combination of CyDs and polysaccharide on the rectal drug delivery were reported. Lin et al. [38] demonstrated that the mixture of (3-CyD and hydroxypropylmethylcellulose (HPMC) markedly reduced the in vivo bioavailability of acetaminophen from both aqueous solution and hydrogels. Not only the lower partition coefficient but also the higher hydrophilic property of the (3-CyD complex and the higher viscosity of HPMC hydrogel matrix might be responsible for the decrease in the in vitro permeation rate and depression of in vivo rectal absorption of acetaminophen. 

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