Pulsatile drug release systems

Details are given of the synthesis of a crosslinked isopropylacrylamide-butyl methacrylate copolymer which has thermo-sensitive swelling behaviour. The copolymer was studied for applications as a thermal on-off switch for a pulsatile drug release system. 2 refs. 

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...

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. 

The direct transport of absorbed drugs into systemic circulation, effectively by-passing the first-pass effect of the liver and gastrointestinal tract Lower enzymatic activity compared to the gastrointestinal tract or liver Amenability to self-medication, which increases patient compliance Possibility of pulsatile delivery of some drugs to simulate the biorhythmic release of these drugs Lower risk of overdosage Achievement of controlled release... 

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. 

The dissolution controlled release matrix systems provide sustained release profiles i.e., the active drugs in these systems are released continuously at a slow rate to provide a long-term therapeutic effect. Unlike diffusion controlled release coated systems, release profiles from dissolution controlled release coated systems do not follow zero-order kinetics but fall within the classification of delayed release systems,4 pulsatile or repeat-action systems,5 and sustained release systems.3... 

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. 

Most pulsatile delivery systems are reservoir devices coated with a barrier layer. The barrier dissolves or erodes after a specified lag time, after which the drug is released rapidly from the reservoir core. In general, the lag time prior to drug release can be controlled by the thickness of the coating layer. 

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... 

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