Release phase

By choosing the excipient type and concentration, and by varying the spray-drying parameters, control was achieved over the physical properties of the dry chitosan powders. The in vitro release of betamethasone showed a dose-dependent burst followed by a slower release phase that was proportional to the drug concentration in the range 14-44% w/w [200]. 

Both processes used to manufacture microspheres produce relatively porous structures. Consequently, release of drugs is generally biphasic, with an initial fast release phase followed by a slower... 

The release mechanism is governed by a modified power law which takes into account an initial release phase that differs from the main release phase 5... 

The recommended dose is 25 mg IM every 2 weeks. Some patients not responding to 25 mg may benefit from a higher dose of 37.5 or 50 mg. The maximum dose should not exceed risperidone injection 50 mg every 2 weeks. Give oral risperidone or another antipsychotic medication with the first risperidone injection and continue for 3 weeks (then discontinue) to ensure that adequate therapeutic plasma concentrations are maintained prior to the main release phase of risperidone from the injection site. 

Later, there is a period of sustained release, typically showing release proportional to indicating that the process of fluoride release is diffusion controlled [228]. Alternatively, in some studies, release has been shown to be proportional to t, which means that for those cements, release is dissolution controlled [232]. This sustained release phase is the one that prevails over long periods of time. For example, Forsten [225] carried out a study in which cement specimens were exposed to running tap water for 5 years, with short periods in static water to allow samples to be collected for analysis, after which they were returned to the running tap water. The data he obtained have been analysed by Billington et al. [233], who showed that the pattern of fluoride release right up to the end of the experiment (i.e., 5 years) continued to show a linear relationship with Fluoride release is thus diffusion controlled for a considerable period of time. 

Similar to the observations by Lee (11,12), the beads undergo great volume expansion during the initial release phase even with poorly soluble DC1 as a result of the osmotic driving force. The... 

After all drug is dissolved, the osmotic pressure decays and the beads shrink to their equilibrium swelling value, as observed for beads with high water swelling (11,12) during this second release phase normal Fickian diffusion kinetics becomes more important, characterized by a very low rate which depends on the hydro-philicity of the polymer. 

Equation 9 describes the zero-order release phase from the frustum. 

Li, X., Deng, X., and Huang, Z. (2001), In vitro protein release and degradation of poly-DL-lactide-poly(ethylene glycol) microspheres with entrapped human serum albumin Quantitative evaluation of the factors involved in protein release phase, Pharm. Res., 18,117-124. 

The above examples show that preparative organometallic chemistry allows for the production of a wide variety of silicon-based molecular precursors for high-temperature ceramics. The desired physical chemical properties and appropriate thermolysis chemistry can be realized by an intelligent precnrsor design. Nevertheless, there is still a need for further development for example, investigations into the synthesis of precursors that release phase-pure ceramics or composites with tunable composition and properties. The focns will also be on designing preceramic polymers, which release functional materials. In this field, very little investigation has been performed so far. 

Aerial radiation measurements and environmental sampling begun shortly after the accident showed that the highest level of environmental contamination was in the area around the reactor that would eventually become the prohibited zone. Elsewhere in the Soviet Union, changing wind conditions and sporadic rainfall over the ten-day release phase resulted in a very uneven pattern of radioactive fallout within areas of the BSSR, the RSESR and the UkrSSR. 

Figure 9 shows a load-change cycle which is typical for discontinuous SCF extraction. When the pressure release phase following completion of the extraction is considered, the question arises as to the true temperature course. It is wellknown that the pressure-dependent equilibrium temperature of CO2 falls to -79 C under atmospheric conditions. This relationship leads to short-term thermal stresses within the inner surfaces of the pressure vessel, particularly in the lower part where dry ice may form. There is an additional risk to the process that the charge may freeze within the pressure vessel. When designing equipment for the extraction of natural substances, definition of the non-stationary courses of pressure and temperature during pressure release is therefore of especial importance in the choice of materials and for the geometry of the pressure vessel. 

In liquid-liquid extraction, a solvent is added to a liquid matrix (feed) to remove selectively transition components by the formation of two coexisting, immiscible liquid phases. The selected solvent (receiver phase) must be capable of preferentially dissolving the solutes to be extracted and be either immiscible or only partly miscible with the carrier (release phase). This process is, therefore, based on the different affinities of the solute distributing between the two coexisting liquid phases. Of the two phases, the solvent-rich solution containing the extracted solute is the extract and the solvent-lean, residual feed mixture is the raffinate. In the case of a closed miscibility gap, the correlation of the solute mole fraction in the extract and the raffinate phase is called the distribution coefficient (partition coefficient) K ... 

The release kinetics are characterized by an initial lag-phase, a zero release phase and a depletion phase. During the lag-phase water intrudes into the polymer matrix and activates the latent catalyst. During the zero-order release phase, an equilibrium between water intrusion and polymer erosion is established and an eroding front, (V2), that penetrates the device is established. Because thin disks were used, device geometry remains essentially constant and zero order release uncomplicated by a decrease in total surface area is observed. The depletion phase characterizes a decrease in device and depletion of the incorporated acidic excipient. 

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