Retarded drug release

This kind of retarded drug release is employed when a rapid rise in blood levels of drug is undesirable, or when absorption is being slowed in order to prolong the action of drugs that have a short sojourn in the body. 

Fig. 20 Thymine-functionalized poly(styrene) for time-retarded drug release...

Enteric-coated systems (ECS) utilize polymeric coatings that are insoluble in the gastric media and therefore, prevent or retard drug release in the stomach. Various types of ionizable polymers are commercially available. They dissolve at various pH ranging between 4.8 and 7.2. ECSs are generally applicable to four major types of drugs ... 

A very intriguing development concerns a drug delivery system for the treatment of periodontitis. It consists of two components. The first is a clay product loaded with tetracycline. The clay product is coated with chitosan to retard drug release. The second component is a thermo-responsive polymer mixed with polyethylene glycol that is syringable at room temperature but solidifies upon warming up to body temperature. The solidified polymer remains 60 min in situ. After that time, it still inhibits the formation of bacterial colonies, and still contains much more of the antibiotic than the control containing no chitosan. 

From these studies the postulated advantages (higher drug load in the matrix lipid core compared to SLN and retarded drug release compared to fat emulsions) of this kind of nanostructured lipid nanoparticles cannot be expected for the formulations studied (e.g. glyceryl behenate/medium chain triglycerides mixtures). 

C.l Kim. PI Lee. F.nhanced anti retarded drug release from hydrophobic ionic bt-ails. J,. Vlacromol Sci. Pure Appl. Chem. A33 1227-1338. 1996. 

In another study, chitin nanofibers were prepared by using deep eutectic solvents (DESs), including mixtures of choline halide (chloride/bromide)-urea and choline chloride-thiourea. The produced chitin nanofibers were utilized for manufacturing calcium alginate bionanocomposite gel beads to improve elasticity and retard drug release [21]. 

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