Stability and enzymatic studies with omeprazole: hydroxypropyl-β-cyclodextrin

The original publication is available at www.springerlink.com. A publicação original está disponível em www.springerlink.comOmeprazole (OME) exhibits low stability to light, heat and humidity. In stress conditions OME stability should improve under inclusion complex form with hydroxypropyl-b-cyclodextrin (HPbCD). Stability of OME, its physical mixture (PM) with HPbCD and OME:HPbCD inclusion complex was assessed during 60 days. The inclusion complexes were prepared by kneading and freezedrying techniques and characterized by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). A molecular modelling was also held to predict the most probable tridimensional conformation of inclusion complex OME:HPbCD. The inhibitory activity of free and complexed OME on selected enzymes, namely, papain (protease model of the proton pump) and acetylcholinesterase (enzyme present in cholinergic neurons and also involved in Alzheimer’s disease) was compared. The results obtained show that HPbCD do not protect against OME degradation, in any prepared powder, in the presence of light, heat and humidity. This may indicate that the reactive group of OME is not included in the HPbCD cavity. This fact is supported by molecular modelling data, which demonstrated that 2-pyridylmethyl group of OME is not included into the cyclodextrin cavity. In relation to enzymatic assays it was observed that free OME and OME in the binary systems showed identical inhibitory activity on papain and acethylcolinesterase, concluding that HPbCD do not affect OME activity on these two enzymes

Layered double hydroxides: A review

267-272Combination of two-dimensional layered materials and intercalation technique offers a new area for developing nanohybrids with desired functionality. Layered double hydroxides (LDHs) are mineral and synthetic materials with positively charged brucite type layers of mixed metal hydroxides. Exchangeable anions located in interlayer spaces compensate for positive charge of brucite type layer. Since most biomolecules are negatively charged, can be incorporated between LDHs. A number of cardiovascular, anti-inflammatory agents are either carboxylic acids or carboxylic derivatives and could be ion exchanged with LDHs to have controlled release. LDHs have technological importance in catalysis, separation technology, medicalscience and nanocomposite material engineering

Trends in floating drug delivery systems

11-21Among novel drug delivery systems, rate controlled oral drug delivery system forms an important area. Research is directed towards overcoming physiological problems, such as short gastric residence times (GRT) and unpredictable gastric emptying times. Prolonged GRT may widen the stomach potential as a drug-absorbing organ. Several approaches are currently utilized in the prolongation of the GRT, including floating drug delivery systems (FDDS), swelling and expanding systems, polymeric bioadhesive systems, modified-shape systems, high-density systems and other delayed gastric emptying devices. Narrow absorption window drugs compounded in such systems have improved in vivo absorption properties. These findings are an important step towards the implementation of FDDS in the clinical setting. In this review, the current technological developments of FDDS including patented delivery systems and marketed products have been discussed. In addition, the pharmaceutical basis of their design, their advantages and future potential for oral controlled drug delivery are discussed