Drug delivery pulsatile release systems

Another approach to the pulsatile delivery of drugs with an osmotic pressure driven system has been suggested by Amidon et al. [66], This system provides the option of an immediate bolus dose and a second dose that can be timed to be released at some subsequent point following the administration of the dosage form. One or both of the doses can be composed of multiparticulates, for example, that would themselves be sustained release systems. 

In this study, we demonstrate new pH/temperature-sensitive polymers with transitions resulting from both polymer-polymer and polymer-water interactions and their applications as stimuli-responsive drug carriers [22-23], For this purpose, copolymers of (Ai,Ai-dimethylamino)ethyl methacrylate (DMAEMA) and ethylacrylamide (EAAm) [or acrylamide (AAm)] were prepared and characterized as polymeric drug delivery systems modulated for pulsatile and time release. 

Polymer-based systems. Pulsatile release of medicaments can be obtained from polymer-based delivery systems. Based on the mechanism of drug release from the polymer, these systems can be divided into various classes and subclasses. Broadly, they can be classified into three classes delivery by hydrolysis of polymers, delivery by osmotic pressure, and delivery by both hydrolytic degradation and osmotic effects. 

Several delivery systems with sigmoidal or pulsatile release patterns were derived on this ion exchange. The sigmoidal release system (SRS) consisted of pellet cores, containing drug and succinic acid, coated with Eudragit The lag time was controlled by the... 

Fig. 6 Pulsatile drug delivery system based on coated effervescent cores—influence of the coating level (7% and 15%w/w) and hardness (50 and 100N) on the drug release/ lag time (coating, EC/DBS core, 30%w/w, effervescent agents, microcrystalline cellulose). (From Ref...

Various pulsatile release methods for oral drug delivery include the Port system (a semipermeable capsule containing an osmotic charge and an insolnble ping) and Chronset system (an osmoticaUy active compartment in a semipermeable cap). 

R. Ishino, H. Yoshino, Y. Hirakawa and K. Noda, Design and preparation of pulsatile release tablet as a new oral drug delivery system, Chem. Pharm. Bull., 40, 3036-3041 (1992). 

One characteristic quality change in this field is that the sharp distinction between active substances and additives has disappeared. The reason for this is that in controlled drug delivery systems the sustained, pulsatile, targeted drug release can almost be regarded as an independent therapeutic effect. 

The development of peptides and proteins as commercially viable therapeutic agents has presented some unique challenges to the drug delivery scientist. Areas where expanded research efforts are important include development of delivery systems with precisely controlled release kinetics—with a particular emphasis on a fundamental understanding of the mechanism of drug release (Shah et ah, 1992) —and further development of pulsatile (e.g., for vaccine delivery), and temporal release systems where the release of drug is consistent with the biochemistry of the disease state. 

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