PubMed · 14867838
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C G BEIRNE, G A BEIRNE. 1951. Water-removable paste.. https://doi.org/10.1001/archderm.1951.01570090117019
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The purpose of this study is to investigate the water granulation mechanism of the hydrophilic matrix polymer HPMC in a high shear mixer and to relate the properties of the granules and tablets to the molecular weight and the degree of substitution for eight HPMC grades. Although the hydrophilic matrix system is a well known drug delivery one, there is a difficulty in that the desirable water granulation technique often causes problems in the presence of relatively large amounts of HPMC due to its hydrophilicity. The results of this study show that the properties of the granules and the tablets fall into two groups according to whether the molecular weight of the polymer is high or low. The granules of low molecular weight were smaller and more compact, with better flow properties but with less tensile strength of the compacts, whereas the opposite was valid for granules of high molecular weight. The explanation for these differences is linked to the proposed granulation mechanism of HPMC, in which the properties of the gel layer are important. The dominant factors governing the properties are the molecular weight and, to lesser extent, the degree of substitution.
Formic acid and its esters, as well as formaldehyde, are trace impurities that are often present in pharmaceutical excipients. These trace impurities can potentially react with amino and/or hydroxyl groups in drugs to form significant levels of degradants. To select the appropriate excipients for a stable formulation, a gas chromatography/mass spectrometry (GC/MS) method was developed and validated for the rapid screening of trace amounts of residual formic acid, its esters and formaldehyde in pharmaceutical excipients. Samples were dissolved or dispersed in acidified ethanol to convert formic acid and formaldehyde to ethyl formate and diethoxymethane, respectively. Identification was conducted using a GC/MS system under scan mode and quantified using a selected ion monitoring (SIM) mode. Evaluation of the mass spectra of ethyl formate and diethoxymethane in the samples indicated that the method is specific. The limits of quantitation of the method were 0.5 ppm for formic acid and 0.2 ppm for formaldehyde. The precision of the method was demonstrated by the acceptable R.S.D. (<or=10%) over a linear range of 0.5-10,000 ppm. The accuracy of the method was within 80-120% over the linearity range. The amounts of formic acid and formaldehyde in commonly used pharmaceutical excipients is reported.
Three sodium carboxymethyl mungbean starches (SCMMSs) were selected, based on the physicochemical profiles and evaluated as potential pharmaceutical suspending agent in comparison with a sodium carboxymethyl tapioca starch and other five commercial suspending agents. Ibuprofen suspension was employed as a model formulation with 0.5, 1.0, and 2.0% w/v of suspending agents. Evaluation parameters included the determination of sedimentation volume ratio, redispersibility, viscosity and rheological properties and content uniformity studies. The results revealed that a high-viscosity modified mungbean starch, MMS-M-04, possessed suitable properties as a suspending agent and, at 1% concentration, was as effective as sodium carboxymethylcellulose and xanthan gum, two most-commonly used suspending agents. This modified starch could be further developed and employed as a new commercial suspending agent in the pharmaceutical industry.