Release of salbutamol sulphate and ketoprofen enantiomers from matrices containing HPMC and cellulose derivatives

Loading of Cefixime to pH sensitive chitosan based hydrogel and investigation of controlled release kinetics

Chitosan (biopolymer) and polyvinyl pyrolidone (PVP) with aminopropyletriethoxy silane (cross linker) based hydrogels were prepared and tested for controlled drug release. The drug release and kinetics were studied as a function of pH. Formulations were characterized by Fourier Transform Infrared (FTIR) and Thermogravimetric (TGA) analysis and TAP 32 hydrogel formulation was the most stable and hydrogel samples showed promising antibacterial activity against E. coli strain. The maximum swelling (4386%) was observed for TAP 32 formulation in distilled water, which was decreased with the concentration of ions. The diffusion exponent (n) values of all hydrogel formulations were recorded to be <0.5, which is an indication of Quasi-Fickian diffusion. The maximum swelling was observed at pH 2 and decreased at higher pH. The pH sensitivity of hydrogels found to be promising for their use in drug delivery, which was tested for cefixime drug. Drug release of 81.6% was observed for the period of 12 h in a simulated gastric fluid (SGF). The values of R² for zero order, first order, Higuchi, Hixson, Korsmeyer-Peppas and Baker-Lonsdale were 0.97, 0.9818, 0.99, 0.99, 0.88 and 0.80, respectively. The hydrogels based on chitosan and PVP revealed potential for controlled cefixime drug release in gastric pH medium.

Stereoselectivity evaluation of chiral chitosan microspheres delivery system containing rac-KET in vitro and in vivo

The influence of chiral excipient D-chitosan (CS) on the stereoselective release of racemic ketoprofen (rac-KET) microspheres has been investigated in comparison to those microspheres containing individual enantiomers in vitro and in vivo. Stereoselectivity was observed in vitro release test, with R-KET release slightly higher than that of S-KET, especially in 3% rac-KET loading microspheres. Stereoselectivity is dependent on the content of chiral excipient and pH of release medium. A molecular docking study between CS and KET enantiomers further revealed that S-KET has a stronger interaction with CS compared to R-KET. Moreover, the plasma concentration of KET enantiomers in rats shows substantial differences, as the plasma levels of S-KET were higher than those of R-KET. Plasma levels of enantiomers from the R-KET microspheres had similar stereoselectivity as rac-KET microspheres. The S/R ratio of rac-KET microspheres was significantly lower than that of rac-KET suspension (regular-release formulation) (p<.05), and the differences is 3–5 fold. Besides, rates of R-KET converted to S-KET exhibited differences between rac-KET microspheres and suspension. Similar results were also found between R-KET microspheres and suspension. All investigations suggest that the chitosan interacting preferentially with S-KET to R-KET significantly affect the stereoselective pharmacokinetics of rac-KET from chitosan microspheres in rats.

Ketoprofen-loaded polymer carriers in bigel formulation: an approach to enhancing drug photostability in topical application forms

The purpose of the study was to investigate the stability and biopharmaceutical characteristics of ketoprofen, loaded in polymeric carriers, which were included into a bigel in a semisolid dosage form. The polymer carriers with in situ-included ketoprofen were obtained by emulsifier-free emulsion polymerization of the monomers in aqueous medium or a solution of the polymers used. The morphological characteristics of the carriers, the in vitro release and the photochemical stability of ketoprofen were evaluated. The model with optimal characteristics was included in a bigel formulation. The bigel was characterized in terms of pH, rheological behavior, spreadability, and in vitro drug release. Acute skin toxicity, antinociceptive activity, anti-inflammatory activity, and antihyperalgesic effects of the prepared bigel with ketoprofen-loaded polymer carrier were evaluated. The carriers of ketoprofen were characterized by a high yield and drug loading. The particle size distribution varied widely according to the polymer used, and a sustained release was provided for up to 6 hours. The polymer mixture poly(vinyl acetate) and hydroxypropyl cellulose as a drug carrier, alone or included in the bigel composition, improved the photostability of the drug compared with unprotected ketoprofen. The bigel with ketoprofen-loaded particles provided sustained release of the drug and had optimal rheological parameters. In vivo experiments on the bigel showed no skin inflammation or irritation. Four hours after its application, a well-defined analgesic, anti-inflammatory, and antihyperalgesic effect was registered. The polymer mixture of poly(vinyl acetate) and hydroxypropyl cellulose as a carrier of ketoprofen and the bigel in which it was included provided an enhanced photostability and sustained drug release.

Guar gum, xanthan gum, and HPMC can define release mechanisms and sustain release of propranolol hydrochloride

The objectives were to characterize propranolol hydrochloride-loaded matrix tablets using guar gum, xanthan gum, and hydroxypropylmethylcellulose (HPMC) as rate-retarding polymers. Tablets were prepared by wet granulation using these polymers alone and in combination, and physical properties of the granules and tablets were studied. Drug release was evaluated in simulated gastric and intestinal media. Rugged tablets with appropriate physical properties were obtained. Empirical and semi-empirical models were fit to release data to elucidate release mechanisms. Guar gum alone was unable to control drug release until a 1:3 drug/gum ratio, where the release pattern matched a Higuchi profile. Matrix tablets incorporating HPMC provided near zero-order release over 12 h and erosion was a contributing mechanism. Combinations of HPMC with guar or xanthan gum resulted in a Higuchi release profile, revealing the dominance of the high viscosity gel formed by HPMC. As the single rate-retarding polymer, xanthan gum retarded release over 24 h and the Higuchi model best fit the data. When mixed with guar gum, at 10% or 20% xanthan levels, xanthan gum was unable to control release. However, tablets containing 30% guar gum and 30% xanthan gum behaved as if xanthan gum was the sole rate-retarding gum and drug was released by Fickian diffusion. Release profiles from certain tablets match 12-h literature profiles and the 24-h profile of Inderal(®) LA. The results confirm that guar gum, xanthan gum, and HPMC can be used for the successful preparation of sustained release oral propranolol hydrochoride tablets.

The use of hypromellose in oral drug delivery

Hypromellose, formerly known as hydroxypropylmethylcellulose (HPMC), is by far the most commonly employed cellulose ether used in the fabrication of hydrophilic matrices. Hypromellose provides the release of a drug in a controlled manner, effectively increasing the duration of release of a drug to prolong its therapeutic effect. This review provides a current insight into hypromellose and its applicability to hydrophilic matrices in order to highlight the basic parameters that affect its performance. Topics covered include the chemical, thermal and mechanical properties of hypromellose, hydration of the polymer matrices, the mechanism of drug release and the influence of tablet geometry on drug-release rate. The inclusion of drug-release modifiers within hypromellose matrices, the effects of dissolution media and the influence of both the external environment and microenvironment pH within the gel matrix on the properties of the polymer are also discussed.

Monitoring release of ketoprofen enantiomers from biodegradable poly(d,l-lactide-co-glycolide) injectable implants

A stereoselective reversed-phase HPLC assay was developed that could simultaneously quantify S-(+) and R-(-) enantiomers of ketoprofen in release samples. Racemic ketoprofen (rac-KET) and its S-(+) enantiomer (S-(+)-KET) were dissolved in an injectable viscous polymer solution consisting of the biodegradable poly(D,L-lactide-co-glycolide, 70:30) (D,L-PLG) and a solvent, N-methyl-2-pyrrolidone (NMP). Once injected into an aqueous environment, the polymeric mixture solidified into a solid implant due to the leaching of NMP. In vitro release studies show that such implants with ketoprofen can provide sustained release of the drug lasting about three months in a pH 7.4 release medium. Moreover, a preferential faster S-(+)-KET release over R-(-)-KET was observed for the implants containing 4%, 7%, and 10% of racemic ketoprofen in the neutral pH 7.4 release medium. Stereoselective release was minimal in the first 42 days in vitro but became very pronounced at later time points. When S-(+)-KET was incorporated into the polymeric mixture, its release was also faster than that of the racemic ketoprofen, confirming the stereoselective release of ketoprofen from the d,l-PLG implants. The observed stereoselective release of KET at pH 7.4 was most likely produced by chiral interactions between KET enantiomers and transiently produced D-lactic acid or L-lactic acid rich domains within the implants during D,L-PLG degradation. However, such stereoselective release was not observed in pH 10.0 release medium, probably due to a much faster and homogeneous polymer degradation. The study suggests possible stereoselective release of racemic drugs from D,L-PLG microspheres and implants in vivo.

Stereoselective behavior of a novel biodegradable racemic ketoprofen injectable implant in rats

The stereoselectivity of release of ketoprofen (KET) enantiomers from a biodegradable injectable implant containing racemic KET (rac-KET) was investigated in vivo. A pre-column chiral derivatization RP-HPLC method was employed to assay diastereoisomeric derivatives of R- and S-KET. The rac-KET injectable implant, once injected subcutaneously in rats, produced long-lasting plasma levels of S-KET, which were always greater than those of R-KET. The difference in enantiomer concentration was to be related to stereoselective release, due to stereoselective interaction between D,L-PLG in the implant and KET enantiomers, as well as the chiral inversion of KET in vivo. The rac-KET injectable implant provided the sustained release of S-KET with effective plasma levels maintained for about 8 wk after a single injection.