Drug-polymer solubility

Drug-polymer solubility has been determined using ... 

Qian F, Huang J, Hussain MA (2010a) Drug-polymer solubility and miscibility stability consideration and practical challenges in amorphous solid dispersion development. J Pharm Sci 99(7) 2941-2947... 

Polster CS, Atassi F, Wu SJ, Sperry DC (2010) Use of artificial stomach-duodenum model for investigation of dosing fluid effect on clinical trial variability. Mol Phatm 7(5) 1533-1538 Puri V, Dantuluri AK, Bansal AK (2011) Investigation of atypical dissolution behavior of an encapsulated amorphous solid dispersion. J Pharm Sci l(X)(6) 2460-2468 Qian F, Huang J, Hussain MA (2010). Drug-polymer solubility and miscibility stability consideration and practical challenges in amorphous solid dispersion development. J Pharm Sci 99(7) 2941-2947... 

Thermodynamic Considerations - Drug-Polymer Solubility and Miscibility... 

Buccal dosage forms can be of the reservoir or the matrix type. Formulations of the reservoir type are surrounded by a polymeric membrane, which controls the release rate. Reservoir systems present a constant release profile provided (1) that the polymeric membrane is rate limiting, and (2) that an excess amoimt of drug is present in the reservoir. Condition (1) may be achieved with a thicker membrane (i.e., rate controlling) and lower diffusivity in which case the rate of drug release is directly proportional to the polymer solubility and membrane diffusivity, and inversely proportional to membrane thickness. Condition (2) may be achieved, if the intrinsic thermodynamic activity of the drug is very low and the device has a thick hydrodynamic diffusion layer. In this case the release rate of the drug is directly proportional to solution solubility and solution diffusivity, and inversely proportional to the thickness of the hydrodynamic diffusion layer. 

The parameters that determine the release rate of a drug from a delivery device include polymer solubility, polymer diffusivity, thickness of the polymer diffiisional path, and the aqueous solubility, partition coefficient, and aqueous diffusivity of the drug. Finally, the thickness of the hydrodynamic diffusion layer, the amount of drug loaded into the matrix, and the smface area of the device all affect the release rate. 

Drug release profiles from the tablets in various dissolution media are shown in Fig. 2. In all cases the release rates decreased initially from the control (distilled water) as electrolyte concentration increased, until a minimum release rate was obtained. As the electrolyte concentration further increased the release rates similarly increased until a burst release occurred. These initial decreases in release rates were probably coincident with a decrease in polymer solubility, in that as the ionic strength of the dissolution medium is increased the cloud point is lowered towards 37°C. It may be seen from Table 5 that minimum release rates occurred when the cloud point was 37°C. At this point the pore tortuosity within the matrix structure should also be at a maximum. It is unlikely to be an increase in viscosity that retards release rates since Ford et al. [1] showed that viscosity has little effect on release rates. Any reduction in hydration, such as that by increasing the concentration of solute in the dissolution media or increasing the temperature of the dissolution media, will start to prevent gelation and therefore the tablet will cease to act as a sustained release matrix. 

Muhrer, G., U. Meier, F. Fusaro, S.AIbano, andM. Mazzotti. 2006. Use of compressed gas precipitation to enhance the dissolution behavior of a poorly water-soluble drug Generation of drug microparticles and drug-polymer solid dispersioriat J Pham308 69-83. 

Solubility of the drug in surrounding medium, including aqueous and polymer solubility... 

The simplest answer is ease of administration. More importantly, there are several limitations to local delivery of drugs in the form of DES. The efficacy of these new devices depends on several variables, including the selection of an effective drug, its solubility, diffusion characteristics, release kinetics, arterial tissue concentration, retention, and whether the platform is polymer based or nonpolymeric. Local delivery of the drug in this manner may delay rather than prevent neointima. This is supported by preclinical studies that show impaired healing and neointimal catch-up (4). There is concern that neointimal growth will accelerate in response to the... 

The release of drug molecules from this type of CrDDSs may be controlled at a preprogrammed rate by controlling the loading level and the polymer solubility of the drug and its diffusivity in the polymer matrix. Several CrDDSs of this type have been successfully marketed for therapeutical uses, and some representatives are outlined later for illustration. 

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