Solubility of guaifenesin in the presence of common pharmaceutical additives

Guaifenesin stone matrix proteomics: a protocol for identifying proteins critical to stone formation

Drug-related kidney stones are a diagnostic problem, since they contain a large matrix (protein) fraction and are frequently incorrectly identified as matrix stones. A urine proteomics study patient produced a guaifenesin stone during her participation, allowing us to both correctly diagnose her disease and identify proteins critical to this drug stone-forming process. The patient provided three random midday urine samples for proteomics studies; one of which contained stone-like sediment with two distinct fractions. These solids were characterized with optical microscopy and Fourier transform infrared spectroscopy. Immunoblotting and quantitative mass spectrometry were used to quantitatively identify the proteins in urine and stone matrix. Infrared spectroscopy showed that the sediment was 60 % protein and 40 % guaifenesin and its metabolite guaiacol. Of the 156 distinct proteins identified in the proteomic studies, 49 were identified in the two stone-components with approximately 50 % of those proteins also found in this patient's urine. Many proteins observed in this drug-related stone have also been reported in proteomic matrix studies of uric acid and calcium containing stones. More importantly, nine proteins were highly enriched and highly abundant in the stone matrix and 8 were reciprocally depleted in urine, suggesting a critical role for these proteins in guaifenesin stone formation. Accurate stone analysis is critical to proper diagnosis and treatment of kidney stones. Many matrix proteins were common to all stone types, but likely not related to disease mechanism. This protocol defined a small set of proteins that were likely critical to guaifenesin stone formation based on their high enrichment and high abundance in stone matrix, and it should be applied to all stone types.

Microencapsulation of a hydrophilic drug into a hydrophobic matrix using a salting-out procedure. I: Development and optimization of the process using factorial design

The congealable disperse phase method for preparing sustained release microspheres involves an emulsification process using water as the external phase and molten hydrophobic wax as the disperse phase into which the drug is loaded. Attempts to entrap highly water-soluble drugs using this process have often resulted in low loading efficiency as the drugs partition into the external water phase during emulsification and are lost. A novel method employing salts and wetting agents was developed to improve the loading efficiency of the highly water-soluble drug, guaifenesin, using this method. The drug/wax ratio (D/W) and the presence of salts and wetting agents greatly influenced microsphere properties. To optimize the process for drug loading efficiency and release rate, three different D/Ws, salts and wetting agents were chosen and a full 3(3) factorial design experiment was performed. Any significant differences among the levels of the variables and their individual and joint effects on entrapment efficiency and T50 (time for 50% drug release) were determined. Entrapment efficiencies in the range 35.1-86.3% were obtained for the various factor-level combinations of the variables. Particle size was in the range 140-385 microm and T50 was 0.59-2.72 h for the microspheres obtained. The D/W and type of salt used significantly affected drug entrapment and T50, while the nature of wetting agent was not significant at p < 0.05. The microspheres prepared using 1:4 D/W showed the highest entrapment efficiency and slowest drug release.

Crystal growth formation in melt extrudates

The purpose of the study was to investigate the physical state of hot-melt extruded guaifenesin tablets containing either Acryl-EZE or Eudragit L100-55 and to study the physicochemical factors influencing crystal growth of guaifenesin on the surface of the extrudates. The powder mixtures containing Acryl-EZE were extruded on a single-screw Randcastle Microtruder at 20rpm and at temperatures of 90, 95, 110 degrees C (zones 1, 2, 3, respectively) and 115 degrees C (die), before being manually cut into tablets (250+/-5mg). Extrudates containing Eudragit L100-55, TEC and guaifenesin were extruded at temperatures ranging from 60 to 115 degrees C. Modulated differential calorimetry (DSC) was used to demonstrate the plasticizing effect of guaifenesin on Eudragit L100-55. Powder X-ray diffraction (PXRD) showed that while the drug powder is crystalline, extrudates containing up to 25% drug exhibited an amorphous diffraction profile. Extrudates containing higher drug concentrations showed an amorphous profile with some crystalline peaks corresponding to guaifenesin, indicating that the limit of solubility of drug in the matrix had been exceeded. Scanning electron microscopy was used to demonstrate that drug crystallization was a surface phenomenon and dependent on the drug concentration. In vitro dissolution testing showed no effect of surface crystallization of guaifenesin on drug release rates of extruded matrix tablets. The influence of hydrophilic polymeric additives including PVP K25, polycarbophil, PEG 3,350, poloxamer 188 or poly(ethylene oxide) as crystal growth inhibitors was investigated at a level of 10% based on the drug content. The extent of crystal growth was reduced for all additives. Complete drug release in pH 6.8 phosphate buffer was prolonged from 4h in extrudates containing Acryl-EZE and guaifenesin to 8h in extrudates containing Eudragit L100-55, TEC and guaifenesin. Drug release in extrudates containing Eudragit L100-55 and guaifenesin was not affected by the presence of hydrophilic additives present at 10% based on the drug content. In vitro drug release studies showed no significant change during storage for up to 6 months at 25 degrees C/60% relative humidity and 40 degrees C/75% relative humidity.

Solubility of (+/-)-ibuprofen and S (+)-ibuprofen in the presence of cosolvents and cyclodextrins

Aqueous solubility is an important parameter for the development of liquid formulations and in the determination of bioavailability of oral dosage forms. Ibuprofen (IB), a nonsteroidal anti-inflammatory drug, is a chiral molecule and is currently used clinically as a racemate (racIB). However, the S form of ibuprofen or S(+)-ibuprofen (SIB) is the biologically active isomer and is primarily responsible for the antiinflammatory activity. Phase solubility studies were carried out to compare the saturation solubilities of racIB and SIB in the presence of common pharmaceutical solvents such as glycerol, sorbitol solution, propylene glycol (PG), and polyethylene glycol (PEG 300) over the range of 20% to 80% v/v in aqueous based systems. The solubilities of the two compounds were also compared in the presence of cyclodextrins such as beta cyclodextrin (CD), hydroxypropyl beta cyclodextrin (HPCD), and beta cyclodextrin sulfobutyl ether sodium salt (CDSB) over the range of 5% to 25% w/v. Solubility determinations were carried at 25 degrees C and 37 degrees C. Cosolvents exponentially increased the solubility of both SIB and racIB, especially in the presence of PG and PEG 300. Glycerol was not very effective in increasing the aqueous solubilities of both compounds, whereas sorbitol solution had a minimal effect on their solubility. PG and PEG 300 increased the solubility of SIB by 400-fold and 1500-fold, respectively, whereas the rise in solubility for racIB was 193-fold and 700-fold, respectively, at 25 degrees C for the highest concentration of the cosolvents used (80% v/v). Of the two compounds studied, higher equilibrium solubilities were observed for SIB as compared with racIB. The derivatized cyclodextrins increased the aqueous solubility of racIB and SIB in a concentration-dependent manner giving AL type of phase diagrams. The phase solubility diagrams indicated the formation of soluble inclusion complexes between the drugs and HPCD and CDSB, which was of 1:1 stoichiometry. The addition of underivatized CD reduced the solubility of racIB and SIB via the formation of an insoluble complex. The S form formed more stable complexes with HPCD and CDSB as compared with raclB. The solubilization process is discussed in terms of solvent polarity and differential solid-state structure of raclB and SIB. The thermodynamic parameters for the solubilization process are presented.