Pulsatile drug delivery systems using hydrogels
ABSTRACT In recent years, temporal control of drug delivery has been of interest to achieve improved drug therapies. Intelligent drug delivery systems (DDS) are one expected result, demonstrating an ability to sense external environmental changes, judge the degree of external signal, and release appropriate amounts of drug. Intelligent DDS may be achieved using stimuli-responsive polymeric hydrogels which alter their structure and physical properties in response to external stimuli. Pulsatile drug release has the advantages of avoiding drug tolerance or matching the body's release of specific peptides or hormones. In this review, recent studies for pulsatile drug delivery in response to stimuli such as chemical agents, pH, electric fields, and temperature are discussed. Achievement of pulsatile drug release from stimuli-responsive polymeric hydrogels as on-off switches and its mechanism are reviewed in terms of control for stimuli-responsive swelling.
- SourceAvailable from: Lida Kalantzi
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- "zero order *Address correspondence to this author at the Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-541 24 Thessaloniki, Greece; Tel: +30 2310 997812; Fax: +30 2310 997667; E-mail: firstname.lastname@example.org release)      . Ideally such systems aim to match drug release rate to a biological requirement of a given disease therapy and thus to manage the disease while minimizing treatment's side effects. "
ABSTRACT: Pulsatile drug delivery aims to release drugs on a programmed pattern i.e.: at appropriate time and/or at appropriate site of action. Currently, it is gaining increasing attention as it offers a more sophisticated approach to the traditional sustained drug delivery i.e: a constant amount of drug released per unit time or constant blood levels. Technically, pulsatile drug delivery systems administered via the oral route could be divided into two distinct types, the time controlled delivery systems and the site-specific delivery systems. The simplest pulsatile formulation is a two layer press coated tablet consisted of polymers with different dissolution rates. Homogenicity of the coated barrier is mandatory in order to assure the predictability of the lag time. The disadvantage of such formulation is that the rupture time cannot be always adequately manipulated as it is strongly correlated with the physicochemical properties of the polymer. Gastric retentive systems, systems where the drug is released following a programmed lag phase, chronopharmaceutical drug delivery systems matching human circadian rhythms, multiunit or multilayer systems with various combinations of immediate and sustained-release preparation, are all classified under pulsatile drug delivery systems. On the other hand, site-controlled release is usually controlled by factors such as the pH of the target site, the enzymes present in the intestinal tract and the transit time/pressure of various parts of the intestine. In this review, recent patents on pulsatile drug delivery of oral dosage forms are summarized and discussed.02/2009; 3(1):49-63. DOI:10.2174/187221109787158337
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- "34 o C) . The abrupt volume change can be utilized in promising application of drug delivery systems       . Several strategies have been reported to realize much more rapid volume change of NIPA gels for better application of them    . "
ABSTRACT: We have investigated rapidly thermo-responsive NIPA gel containing polymer surfactant PMDP (NIPA-PMDP gel) as a potential drug carrier using (+)-l-ascorbic acid as a model drug. In the NIPA-PMDP gel system micelles of polymer surfactant PMDP are trapped by the entanglement of polymer chains inside the gel networks. Therefore, in principle the gel system tightly stores targeted drug in the micelles and rapidly releases controlled amount of the drug by switching on-off of external stimuli such as temperature or infrared laser beam. In our investigation on release profile, the NIPA-PMDP gel system showed completely different releasing behavior from that of the conventional NIPA gel. The NIPA-PMDP gel released rapidly all loaded (+)-l-ascorbic acid above the phase transition temperature (ca. 34 degrees C), while slowly released the corresponding amount of the drug below the temperature. In contrast, the conventional NIPA gel released more slowly limited amount of the drug above the phase transition temperature while similarly did to the NIPA-PMDP gel below the temperature. The release profile of the NIPA-PMDP gel seems to be governed by only kinetics of volume phase transition of the gel network but not by the hydrophobic domains of the micelles probably because of too hydrophilic nature of (+)-l-ascorbic acid.Colloids and surfaces B: Biointerfaces 01/2006; 46(3):142-6. DOI:10.1016/j.colsurfb.2005.10.007