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A water-insoluble complex between diltiazem HCl and Na deoxycholate was prepared to achieve sustained release dosage forms. Physicochemical characterization of the drug complex was carried out with differential scanning calorimetry, (1)H-nuclear magnetic resonance, and Fourier transform infrared spectroscopy. These techniques showed that the characteristic peaks in both the drug and the complexing agent (protonated amine and carboxylate) disappeared and new peaks appeared upon formation of the ionic complex. The release of diltiazem from drug-complex tablets was sustained for a long period of time (24 h) and was dependent on the pH of the dissolution medium. However, the dependence of drug release on pH was eliminated at pH 6-8 and minimized at pH 1.5 when drug-complex powders were incorporated in hydroxypropylmethylcellulose (HPMC) drug carriers. Unlike the release of diltiazem HCl from HPMC drug carriers, drug release from drug-complex/HPMC tablets was linear or near linear irrespective of the viscosity grade of the polymer (E15 to K4M). This is due to a shift in the controlling mechanism of drug release from drug diffusion to erosion of polymer. Also, drug release kinetics was not significantly affected by the water solubility of cationic drugs (diltiazem HCl, verapamil HCl, propranolol HCl, and labetalol HCl) ranging from 1.6 to 62% and the type of amine (i.e., secondary or tertiary). The same release characteristics were observed from the complexes between anionic drugs (Na salicylate, naproxen Na, and tolmetin Na) and benzathine diacetate as found from the complexes between cationic drugs and Na deoxycholate.

A rapid and sensitive high‐performance liquid chromatographic method was developed for the determination of propylthiouracil. The chromatographic system utilized a C8 column with the detector wavelength set at 276 nm. The mobile phase was composed of water and methanol in a 70:30 (v/v) ratio and was delivered at a flow rate of 0.5 mL/minute. The analytical run time was less than 7 min. The standard curves were linear over a range of 1–100 µg/mL with a correlation coefficient of 0.9958. The limit of quantification was assessed to be 15 ng and the limit of detection 4.5 ng. The RSD values for the intra‐ and inter‐day precision studies were 0.11–1.28% and 1.65%, respectively. The accuracy was ≤5% over the concentration range 1–100 µg/mL. The stability‐indicating nature of the assay method was determined by subjecting a stock solution of propylthiouracil to extremes of acidic and basic degradation. It was found that the method was specific for propylthiouracil. Hence, a simple, rapid, sensitive, stab...

It has been observed that hindered settling experiments usually lead to voluminous data, which is usually characterized as “poorly reproducible”. Many factors might affect these techniques. The ability to control these parameters may result in a better analysis of the outcome and the correct estimation of the particle size. An attempt was made to investigate calcium oxalate monohydrate stability in the presence and absence of cholesterol, while determining the factors which may undermine the results obtained. The data may provide interesting information which may be used in other similar investigations to reduce the negative compacts caused by the low reproducibility. *Posthumously.

A new viscosity–capillary dipometer was designed and used in this investigation. Comparing this piece of equipment with other viscometers, the capillary dipometer is accurate, easy to operate, and much less expensive. The viscosities for calcium hydrogen phosphate and calcium oxalate suspensions are determined using the capillary dipometer. The data shows that this method is suitable for suspensions. This method could also be applied to other liquid dosage forms (i.e., emulsions) to provide quick and accurate results.

The purpose of this study was to identify the degradation products for folic acid which may form under thermal stress. An attempt was made to identify each of the decomposition products using various analytical techniques, such as infrared spectroscopy, mass spectroscopy, and X-ray diffraction, which suggested that the glutamic acid fragment of folic acid is lost first, as evidenced by acid loss and amide enhancement in the IR spectra. The vitamin was ultimately degrading to carbon fragments and further identification was not necessary.

A new titration method proposed by Huyhn et al., which directly measures the interparticular pore volume between the particles in a concentrated suspension, has been further investigated. It is expected that for an ideal powder with uniform spherical particles, the plot of weight versus the void volume should be a straight line passing through the origin. Glass beads, which are nonporous and expected to be ideal, were used in this study and the results were compared with the results of the experiments by Huyhn et al. Glass beads of different size ranges are used to study the effect of particle size on voidage. It was observed that the voidage increases with a decrease in particle size, However, the non-porous glass beads were also found not to be ideal.

Nicotinic acid belongs to the B group of vitamins and is often referred to as Vitamin B3. It is an essential component of a balanced diet and is prescribed as tablet, and in parenteral dosage forms in cases of vitamin deficiency. This study involves a preliminary preformulation study to assess whether nicotinic acid is a good candidate for tablet and capsule manufacture. The manufacturing process for solid dosage forms involves high energy-intensive processes, which mainly include grinding and compaction. The effect of these high-energy processes on the stability of nicotinic acid was evaluated using thermogravimetry (TG) as the primary analytical tool. The initial stage involved characterizing the thermal behavior of the material. It was found that nicotinic acid shows a solid-solid state phase transition, which is reversible. This transition appears as a small endothermic peak on the differential thermal analysis (DTA) curve, just before the dual sublimation-evaporation stage. This was followed by study...

The heat treatment of parahydroxy benzoic acid esters follows zero order rate processes that are in good correlation with their evaporation process. Rising temperature experiments were performed and the optimum conditions were found when the heating rate was 10°C/min in an atmosphere of dry nitrogen, the flow rate of which was maintained at 100 mL/min. The Antoine constants for methyl paraben were substituted into the Antoine equation to get the corresponding vapor pressures that were then used in the Langmuir equation to obtain the value for the coefficient of evaporation k . The Eact value, obtained from the Arrhenius plot, was 75.1 kJ mol−1; the enthalpy of vaporization (ΔHvap) was calculated to be 77.9 kJ mol−1, in very close agreement with the Eact value. Using the Antoine and Langmuir equations, the value of k was experimentally determined to be 124525 ± 0.8, units being in the S.I. system. Taking the value of k to be independent of the substance, the corresponding vapor pressures were obtained for ...

Dolomite decomposes via a 2-stage mechanism in an atmosphere of CO2. The first stage of the decomposition was analyzed in depth using both isothermal and rising temperature kinetics. It was found that the first stage of decomposition follows the Avrami-Erofeev A2 mechanism for the isothermal experiments. However, for the rising temperature experiment, the reaction follows the Avrami-Erofeev A4 mechanism. The energy of activation (Ea) obtained for the isothermal experiments was determined to be 424.97 kJ/mol, while the value for the rising temperature experiment was 647.20 kJ/mol. Similarly, the ln A-value for the isothermal experiments was found to be 49.22, while the ln A-value for the rising temperature experiment was 74.20. The effect of procedural variables on the thermal behavior of dolomite in a nitrogen atmosphere is investigated. The program design variables include alterations in the flow rate, heating rate, grain size, and sample size. Out of these variables, heating rate, flow rate, and grain s...

This study prepared an extemporaneously formulated liquid suspension dosage form (5 mg/ml) from commercially available 25 mg tablets. Stability-indicating HPLC assay procedures were established and utilized to analyze the concentration of the drug. The method proved to be a simple model since it does not contain a buffer system. The mobile phase used was the same as that suggested by the manufacturer for the storage of the column. Therefore, the solvent system saves analytical processing time, since it does not require a change in the mobile phase before or after the analysis. The analytical method has been shown to be stability-indicating. The results have shown that there is no interference from any of the degradation products obtained from stressing spironolactone by heat and extremes in pH or with the internal standard, hydrocortisone 21-acetate.

Steinour and Richardson and Zaki proposed relationships to explain the hindered settling phenomena from their independent experiments about 10 years apart. An attempt has been made to compare the coefficients and derive a relationship between Steinour's parameter A and Richardson and Zaki's parameter n. It is possible to express this relationship in the form of an equation involving parameters for which values can be assigned. Theoretically, this derived relationship should be applicable to any sedimenting suspension which obeys both Steinour's and Richardson and Zaki's equations. This derived expression has been evaluated for various experimentally determined values of A and n. The experimental systems which have been tested include calcium carbonate suspensions in water, sucrose-water, and glycerin-water solutions, and ethyl alcohol and magnesium hydroxide suspensions in glycerin-water, sucrose-water and sorbitol-water solutions. The calculated values have been shown to agree well with experime...

A high performance liquid chromatographic (HPLC) method for the quantitation of acetazolamide in a suspension dosage form is described. The method is simple, accurate, and precise. Acetazolamide was extracted from the suspension using a mobile phase which contained 65% phosphate buffer and 35% methanol and separated from other components by reversed-phase high performance liquid chromatography. The separation was carried out using a C18 column (250 × 4.5 mm i.d.). The photometric detector was set at 254 nm. The excipients present in the tablets from which the suspension was compounded did not interfere with the assay procedure. Sixteen replicate injections of 10.5 mg/mL samples resulted in a percent relative standard deviation of 2.02.

The solubilities of several sulfonamides were studied at three temperatures over a wide spectrum of polarity of normal alcohols. The sulfonamides chosen for study were sulfasoxaeole, sulfadimethoxine, sulfasomidine and sulfadiazine and their solubility behavior in various alcohols such ae methanol through 1-decanol at 25°. 30° and 37°.Solubility in alcohols was found to increase with temperature and the rank order of solubility at any temperature wae found to be in the general order of sulfasoxizole, sulfadimethoxine, sulfasomidine and sulfadiaeine. Solubility was found to be highest in methanol and diminished with increasing chain length of the alcohol.The solubility magnitude for several of the sulfonamides gave an interesting reversal in 1-decanol and all the results obtained are discussed further in this communication.

The effect of flocculant materials on kaolin-water suspensions is reported using two kaolins. One of these is a pharmaceutical-grade kaolin and the other an industrial kaolin. These two systems serve as a model in a broader investigation which will systematically study the ancillary ingredients of pharmaceutical kaolin-based suspensions. These studies are based on concentrated suspensions where fall of particles is hindered and characterized by sedimentation “en bloc” with a sludge line serving as interface between the supernatent liquid and the settling suspension. It is shown that there is an optimum concentration of macromolecular flocculant which causes maximum flocculation. At higher concentrations of flocculant the system is stabilized. Two approaches are used to explain the results. The first represents the phenomenon as a modification of Stokes Law results. A correlation is found between the parameter A used as a characterization constant in Steinour's empirical relationship and the Richar...