Time-controlled release drug delivery

Controlled release drug delivery systems are used to deliver the drug locally or system cally at a predetermined rate for a specified period of time [55-57], These systems are used to provide desirable delivery profiles that can achieve therapeutic plasma levels [58,59,55]. In these systems, the drug release is dependent on polymer properties, thus the application of these properties can produce well-characterized and reproducible dosage forms [60]. This section will focus on the two major types of systems micro-spheres/nanoparticles and tablets. 

FIGURE 22.8 Steady-state plasma pro les of immediate-release nifedipine (Three times a day) and Procardia XL on day 5. (Adapted from V fong, P., et al.,Modified-Release Drug Delivery Technolp y. J. Rathbone, et al. (Ed.), Osmotically Controlled Tablets, Marcel Dekker, Inc., p. 107.)... 

This time controlled release tablet with a designated lag time followed by a rapid release may provide an alternative to site-specific delivery of drugs with optimal absorption windows or colonic delivery of drugs that are sensitive to low pH or enzyme action for the treatment of localized conditions such as ulcerative colitis, Crohn s disease, and irritable bowel syndrome (IBS). Also, by controlling a predetermined lag time of drug from dosage form, the release behavior can be matched with the body s circadian rhythm pattern in chronotherapy. 

Niwa, K., Takaya, T., Morimoto, T., and Takada, K. (1995), Preparation and evaluation of a time-controlled release capsule made of ethylcellulose for colon delivery of drugs, J. Drug Target., 3, 83-89. 

Biotextiles can be converted to various preparations to provide needed drug delivery profiles, such as sustained-release, time-controlled release, targeted drug release, smart drug release profiles, etc. 

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