Biomedical subjects

M S Bergren

Publications and source records attributed to M S Bergren.

5 recordsLinked to original sources

PubMed1999

Tablet dissolution affected by a moisture mediated solid-state interaction between drug and disintegrant.

PURPOSE: To investigate the cause for decrease in delavirdine mesylate 200 mg tablet dissolution upon exposure to high humidity. METHODS: Dissolution testing was performed using the USP 2 (paddle) apparatus. Water in tablets was measured by Karl Fischer titration. 13C CP/MAS NMR was used to identify and quantify delavirdine form changes in tablets. FT-IR spectroscopy was used to monitor delavirdine form change in tablets and component mixes, and to investigate a solid state reaction with the disintegrant. RESULTS: Dissolution extent of delavirdine mesylate 200 mg tablets was substantially decreased after exposure to high humidity. This effect is related to the amount of water present in the tablet matrix. 13C CP/ MAS NMR detected about 30% conversion from the mesylate salt of delavirdine to its free base form in the tablet matrix. FT-IR spectroscopy demonstrated that a solid state reaction occurs between the freed methanesulfonic acid and the carboxyl sites on the croscarmellose sodium disintegrant. CONCLUSIONS: Water is thought to act as both a reaction medium and a plasticizer for croscarmellose sodium, facilitating protonation of the carboxyl sites on the disintegrant. This reaction has the potential to occur for any acid salt of a free base. The limiting solubility of delavirdine free base formed in the tablets accounts for much of the decrease in the extent of dissolution. A change in inter-particle bonding can explain the reduction in tablet deaggregation during dissolution.

Carboxymethylcellulose Sodium↗

PubMed1997

Characterization and interconversion of polymorphs of premafloxacin, a new quinolone antibiotic.

The quinolone antibiotic premafloxacin crystallizes in at least five solid modifications, including three anhydrous phases (Forms I-III), a hydrate, and a methanolate. The anhydrous phases were studied by optical microscopy, X-ray powder diffraction, HPLC, hot-stage microscopy, dynamic moisture sorption gravimetry, differential scanning calorimetry, thermal gravimetry, and solution and isothermal calorimetry. Dry samples of Form I converted to Form II and ultimately to Form III through a sequence of melts and recrystallizations. Form III was stable to its melting temperature near 200 degrees C. Humidified samples of Form I converted directly to Form III via a moisture-mediated solid-state phase transformation at temperatures as low as 40 degrees C. The calorimetric and solubility data confirmed that Form III was lower in free energy and enthalpy than Form I at room temperature. Our investigation revealed that Form I was not crystallized directly from solution. Rather, Form I was the product of facile solid-state desolvation of the methanol solvate.

Anti-Infective Agents↗

PubMed1996

Solid phases of delavirdine mesylate.

Delavirdine mesylate was recrystallized from solution under a variety of conditions. Seven crystal forms and a stable amorphous phase were isolated from solution. Two of these crystal forms were polymorphic anhydrates: from XI (U-90152T) and form VIII (U-90152S). Two hydrates (forms VI and XIV), an ethanol solvate (form VII), an acetonitrile solvate (form XIII), and a solvate from methanol/acetone (from XII) were also identified. Six additional phases were identified as the products of solid-state transformations of the hydrated and solvated phases. The solid phases were differentiated by infrared spectroscopy and X-ray powder diffraction. Several of the solid-state phase transformations were mediated by atmospheric moisture. These transformations were studied as a function of relative humidity with dynamic moisture sorption gravimetry (DMSG). DMSG also provided useful measurements of hygroscopicity.

Acetonitriles↗

PubMed1989

Analysis of solvent residues in pharmaceutical bulk drugs by wall-coated open tubular gas chromatography.

A simple general method for the determination of solvent residues in drugs is described. The procedure is based on wide-bore wall coated open tubular (WCOT) gas chromatographic analysis of bulk drug solutions. The use of wide-bore WCOT columns with chemically crosslinked methyl silicone stationary phases offers improvements in specificity and sensitivity over earlier packed-column methods. The factors that influence method accuracy are discussed, including a consideration of instrumental and matrix contributions to the linearity and bias of the method. Some problems with interferences peculiar to benzyl alcohol are reported.

Chromatography, Gas↗

PubMed1989

Investigation of the relationship between melting-related parameters and in vitro drug release from vaginal suppositories.

The effect of temperature on drug release from meteneprost potassium vaginal suppositories was investigated using a dissolution test based on the USP I apparatus. Comparison of the dissolution results with the DSC melting behaviour revealed that drug release was extremely slow until melting of the suppository was essentially complete. The melting behaviour of the meteneprost potassium suppositories was also varied by preparing suppositories from bases with higher and broader melting ranges. The observed dissolution behaviour (at 37 degrees C) confirmed that drug release increased as the melting temperature of a particular suppository decreased. Differential scanning calorimetry, viscosity and dilatometry methods were used to characterize the suppository melting process. The effects of suppository melting range, melt temperature and composition were investigated with respect to in vitro drug release. Methodology for the HPLC determination of meteneprost in suppositories and in dissolution media are also reported.

16,16-Dimethylprostaglandin E2↗