Drug delivery dissolution-controlled release

Future Potential for Dissolution Controlled Release Drug Delivery Systems... 

Currently, most mature dissolution controlled release systems/ technologies are applicable for water-soluble and low-water-solubility compounds (with low doses). For very poorly water-soluble compounds, dissolution controlled release systems/technologies may not be applicable because these compounds have intrinsically slow dissolution/release rates. Recently, several new technologies such as solid dispersions and self-emulsifying drug delivery systems (SEDDS) have been developed to deliver poorly water-soluble compounds at reasonable doses through enhancement of dissolution rate. These technologies have created new potentials for controlled release of poorly water-soluble compounds, often... 

Figure 1. Mechanisms of controlled release drug delivery. Diffusion-controlled (A), dissolution-controlled (B), osmoticSly controlled (C), ion-exchange controlled (D), and degradation-controlled (polymeric prodnig, E) systems.

Peppas, N. A., A model of dissolution-controlled solute release from porous drug delivery polymeric system, J. Biomed. Mater. Res., 17. 1079, 1983. 

For an erosion-induced drug delivery system compactable cellulose ethers are suitable polymers [103]. Drug release, which is controlled by the erosion/dissolution of these polymeric layers, may be pH-dependent if an acid or basic polymer is used. 

FIGURE 22.7 Azero-order release pro le with release duration of 24 h and independent of the pH ofthe dissolution medium. (Adapted from V fong, P., etal.,Modified-Release Drug Delivery Technolpt J. Rathbone, et al. (Ed ), Osmotically Controlled Tablets, Marcel Dekker, Inc., p. 107.)... 

The majority of controlled drug delivery systems now being marketed or under development are based on diffusion of the drug through a semipermeable membrane to achieve the requisite release rate. Diffusion control is particularly important to transdermal delivery, where biodegradation and dissolution are not viable mechanisms of controlling the release rate. Provided the process is Fickian, the rate of diffusion through the semipermeable polymer is determined by... 

Siepmann, J., Kranz, H., Bodmeier, R., and Peppas, N., HPMC-matrices for controlled drug delivery A new model combining diffusion, swelling, and dissolution mechanisms and predicting the release kinetics, Pharmaceutical Research, Vol. 16, No. 11, 1999, pp. 1748-1756. 

Dissolution rate tests for tablets, capsules, suspensions, suppositories, or other dosage forms. Controlled-release dosage forms or drug delivery systems also should be monitored by appropriate testing methodology. 

Fig. 17 Syncro-Mate-C implant, a subdermal implant fabricated from the microreservoir dissolution-controlled drug-delivery system, and subcutaneous controlled release of nor-gestomet, a potent synthetic progestin, at constant rate for 20 days. The open ends on the implant do not affect the zero-order in vivo drug release profile. (Adapted from Ref. . )...

Fassihi RA, McPhillips AM, Uraizee SA, Sakr AM. Potential use of magnesium stearate and talc as dissolution retardants in the development of controlled release drug delivery systems. Pharm Ind 1994 56 579-583. 

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