Osmosis-controlled drug release

Osmotic pressure can be used for controlled drug release. The osmostic pressure can pump out drug at a constant rate, as described below. An important consideration is that because the pumping principle is based on osmosis, pumping rate is unaffected by changes in experimental conditions. Hence, in vitro drag release rate is often consistent with the in vivo release profile. 

The insoluble cellulose derivatives utilized for permeation control of various species (e.g. oxygen and water vapor transport in coated pharmaceuticals, contact lenses, packaging, or water and solute transport through semi-permeable membranes in reverse osmosis, as well as drug release from reservoir systems) differ considerably in their permeability characteristics according to the type and extent of substitution, as well as their molar mass. However, very few comparative data are available from the literature on the polymers actually used in biological applications. Recently, new results have been published. Thus, Sprockel et al. [142] determined the water vapor transmission through various CA, CAT, CAB and CAPr films at different relative humidities (Table 22). 

An approach for feedback control of polypeptides incorporated within polymeric drug delivery systems was also developed. This approach is based on the observation that changes in pH can cause dramatic shifts in the solubility of polypeptide drugs solubility is one of the prime determinants of release rate in any diffusion-, dissolution-, or osmosis-controlled release system. The system components involve an external trigger molecule... 

Solid state drug release systems controlled with coating are called membrane diffusion or reservoir systems [36, 37]. The process of drug release is illustrated in Figure 18.6. The driving force of the process is diffusion and the phenomenon of osmosis [22, 37, 38, 40]. 

The release rate of a drug out of a pharmaceutical dosage form can also be controlled by the hydrostatic pressure, which is built up upon water influx into the system that is driven by osmosis (35-37). Figure 5 illustrates two types of systems a one-chamber device and a... 

Edible film Controlled moisture transfer between food and the surrounding environment Controlled release of antimicrobial substances Controlled release of antioxidants Controlled release of nutrients, flavors, and drugs Reduction of oxygen partial pressure Controlled rate of respiration Temperature control Controlled enzymatic browning in fruits Reverse osmosis membranes... 

Additional present and potential applications involving polymeric membranes include controlled release of drugs for medical applications, electrical power generation from forward osmosis and reverse elearodialysis, biomedical applications including hemodialysis and diagnostic applications, bioanalysis, sensors, and electrochromic displays. ... 

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