Biomedical subjects

N Sarisuta

Publications and source records attributed to N Sarisuta.

6 recordsLinked to original sources

PubMed2004

Influence of methylation process on the degree of quaternization of N-trimethyl chitosan chloride.

N-Trimethyl chitosan chloride (TMC) is a soluble chitosan derivative that shows effective enhancing properties for peptide and protein drug transport across mucosal membranes. TMC was synthesized by reductive methylation of chitosan in an alkaline environment at elevated temperature. The number of methylation process steps and the base used in the process was demonstrated to affect the degree of quaternization of the primary amino group and methylation of 3- and 6-hydroxyl groups. 1H-Nuclear magnetic resonance spectra showed that the degree of quaternization of TMC was higher when using sodium hydroxide as the base compared to using dimethyl amino pyridine. The degrees of quaternization as well as O-methylation of TMC increased with the number of reaction steps. O-Methylation resulted in decreased solubility of TMC. The high degree of quaternization of TMC with a low degree of O-methylation was prepared by employing one reaction step with two subsequent addition steps and a controlled alkaline environment of the mixture reaction.

Chemistry, Pharmaceutical↗

PubMed2000

Dissolution kinetics of three-component compressed solid mixtures with largely different solubilities: flaking spheres.

The dissolution kinetics of three-component compressed solid spheres of various compositions of mannitol (MAN), sulfamethoxazole (SMX), and trimethoprim (TMP) were studied. Because the solubility of MAN was approximately 300 times that of SMX and TMP, the flaking phenomenon during dissolution process was observed. The critical flaking line was drawn between two critical flaking points in the triangular composition diagram of MAN-SMX-TMP mixtures (i.e., the compositions of 0.5022 MAN and 0.4978 SMX mass fractions, and 0.4906 MAN and 0.5094 TMP mass fractions), thus dividing the system into two distinct regions; namely, nonflaking and flaking regions. In the case of nonflaking region, only three dissolution behaviors for MAN-SMX-TMP three-component mixtures were proposed. The calculated dissolution rates of all components by using the multicomponent dissolution model previously proposed were found to satisfactorily approximate the observed values for both two- and three-component solid mixtures. In the case of flaking region, the observed dissolution rate of MAN was found to be the exponential function of the mass fraction ratio of either SMX or TMP to MAN for both two- and three-component mixtures. The slope of the semilogarithmic plot of the observed MAN dissolution rate versus the mass fraction ratio of either SMX or TMP to MAN was defined as retarding coefficients of SMX or TMP, r'(SMX) or r'(TMP), respectively. The erosion rate of either SMX or TMP was the product of mass fraction ratio of drug to MAN and the exponential function of such mass fraction ratio. The mathematical model was developed on the basis of simultaneous erosion followed by dissolution of eroded particles to predict the dissolution rate of each drug from MAN-SMX-TMP compressed solid spheres within the flaking region.

Chemistry, Pharmaceutical↗

PubMed2000

Physical structure characterization of theophylline in some acidic film-forming polymers.

The physical structure and drug-polymer interactions of theophylline in Eudragit L100, shellac, polyvinyl acetate phthalate (PVAP), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose acetate phthalate (HPMCP), and hydroxypropylmethylcellulose (HPMC) were studied. The drug-polymer films were prepared by casting and were characterized using powder X-ray diffractometry (PXRD), nuclear magnetic resonance (NMR) spectroscopy, and thin-layer chromatography (TLC). Theophylline was found to recrystallize in the modification II form in all kinds of polymers, which was the same as that recrystallized solely from the solvent system and the original powder. The PXRD and NMR results indicated a superficial drug-polymer interaction between theophylline and Eudragit L100, while there was no evidence of interaction for the others. No drug decomposition was observed by TLC for all drug-polymer mixtures.

Cellulose↗

PubMed1999

Physico-chemical characterization of interactions between erythromycin and various film polymers.

In this study the interactions between erythromycin and various polymers (Eudragit L100, shellac, polyvinyl acetate phthalate (PVAP), cellulose acetate phthalate (CAP), hydroxypropyl methylcellulose acetate phthalate (HPMCP), and hydroxypropyl methylcellulose (HPMC)) were investigated. The polymer films containing drugs were prepared and characterized by the use of infrared spectroscopy, powder X-ray diffraction analysis, thermal analysis, thin layer chromatography, and nuclear magnetic resonance (NMR) spectroscopy. Preliminary studies of pure drug powders recrystallized in various organic solvent systems suggested a mixture of amorphous and crystalline forms whereas those recrystallized in water and organic solvent-water mixture led to the dihydrate form. Erythromycin in drug-polymer mixtures exhibited molecular dispersions in all six polymers studied. The amine salt interaction between the carboxyl group of the acid polymers and N-atom of erythromycin was indicated by the NMR technique. The solid solution of erythromycin in all polymer films studied was physically stable under stress conditions (8 degrees C/3 days and 40 degrees C/3 days for six cycles).

Anti-Bacterial Agents↗

PubMed1999

Effects of surfactant on release characteristics of clonidine hydrochloride from ethylcellulose film.

The effects of Tween 80 (polysorbate 80) and Span 80 (sorbitan monooleate) surfactants on release characteristics of clonidine hydrochloride from ethylcellulose 10 and 20 cps matrix films containing castor oil as a plasticizer were investigated. The release rates of drug from these films in water at 37 degrees C were found to increase with the addition of surfactant, which was highest for the film prepared from ethylcellulose 20 cps with Tween 80. The experimental values of the cumulative amount of drug released were found to conform to the solution matrix model. The calculated values of the cumulative amount of clonidine hydrochloride released using the experimentally determined diffusion coefficients were also found to be in good agreement with the observed values.

Algorithms↗

PubMed1982

Relationship of dissolution rate to viscosity of polymeric solutions.

The influence of viscosity on the dissolution rate of benzoic acid in aqueous solutions of methylcellulose, hydroxypropyl cellulose, and guar gum was investigated. The viscosities were measured by capillary and rotational viscometers and were calculated from experimental diffusion coefficients by means of the Stokes-Einstein equation. The relationship of the dissolution rate to viscosity may be represented by a single curve. An equation is presented relating the dissolution rate of benzoic acid to solubility, diffusion coefficient, and viscosity for these nonionic viscosity-enhancing agents. To demonstrate that additional factors affect the dissolution rate, similar data were determined using solutions of xanthan gum, which is anionic. The electrical effect modified mass transport so the quantitative relationship of dissolution rate and viscosity was not the same as in the nonionic carbohydrate solution.

Benzoates↗