Solubility and dissolution rate of ibuprofen in ionic and non-ionic micellar systems.

Equilibrium solubility, the profile and the rate of ibuprofen dissolution in solutions of sodium dodecyl sulfate, Tween 60 and Brij 35 were studied. It was found that the solubility of ibuprofen was enhanced by the formed micellar system. The size and shape of formed micelles depended on the used particular surfactant. The mechanism of ibuprofen dissolution in micellar system was discussed.

Determination of amezinium in plasma by RP HPLC and its application to bioequivalence studies.

A modified method is described for the determination of 4-amino-6-methoxy-l-phenylpyridazinium methyl sulfate (amezinium metisulfate) in plasma and in the dosage form. The method involves a sample preparation using SPE and liquid-liquid extraction and subsequent determination by high performance liquid chromatography. Retention time for amezinium was 3.2 min and there was no interference from plasma or amezinium metabolites. The method was applied for the drug determination during comparative studies of two different tablet formulation of amezinium.

Simultaneous determination of salicylic acid and acetylsalicylic acid in aspirin delayed-release tablet formulations by second-derivative UV spectrophotometry.

A rapid, simple assay procedure was developed for simultaneous analysis of aspirin (ASA) and salicylic acid (SA) in aspirin delayed-release tablet formulation by 'zero crossing' second-derivative UV spectrophotometry. The zero-order absorption spectra and second derivative spectra of ASA and SA were recorded in diluting solution acetonitrile-formic acid (99:1). The accuracy of the method was demonstrated by the determination of ASA and SA in five tablets formulations (each 20 tablets of the same batch) by the described method and by high performance liquid chromatographic method, and the results were in good agreement.

Complexes of Fe(III) ions with mefenamic acid.

Mononuclear and binuclear complexes of mefenamic acid with Fe(III) ions of formulae Na[Fe(C15H14O2N)4] and Fe2Cl(C15N14O2N)5 were obtained in the solid phase. Characterization of the complexes was performed by elemental analysis and visible, IR, 1H and 13C NMR spectroscopy and possible structures are proposed.

Effect of pepsin on the kinetics of HCl neutralization by dihydroxyaluminum sodium carbonate, hydrotalcite and dihydroxyaluminum aminoacetate.

The rate of HCl neutralization by dihydroxyaluminum sodium carbonate (DHASC), hydrotalcite (HT) and dihydroxyaluminum aminoacetate (DHAAA) in the presence of different amount of pepsin (PP) has been studied at constant pH = 3.0. The results can be explained using Weibull distribution function by comparing the kinetical parameters with and without the substance added and as a function of their concentration. Some aspects of mechanisms of inhibition or acceleration of acid neutralization of DHASC, HT and DHAAA by PP are also discussed.

Studies of neutralizing properties of antacid preparations. Part 7. 27Al NMR studies of aluminum species formed during acid dissolution of some antacid preparations.

Neutralization of some aluminum containing antacid preparations with hydrochloric acid were studied by 27Al NMR spectroscopy. It has been found that the nature and composition of aluminum species produced during the acid dissolution of preparations depends upon the substance used and on the pH at which the neutralization reaction proceeds. The results are consistent with the presence of both monomeric and polymeric species in solution containing aluminum in octahedral and tetrahedral environments.

Studies of neutralizing properties of antacid preparations. Part 5: Dissolution kinetics of dihydroxyaluminum aminoacetate.

The acid dissolution process of dihydroxyaluminum aminoacetate (1) has been studied by pH-stat method. The neutralization reaction was examined by monitoring the appearance of aluminum ion and aminoacetic acid in the reaction medium. The Weibull distribution function was applied to the quantitative interpretation of neutralization rate data. The mechanism of acid neutralization of 1 is discussed.

[Studies of physico-chemical properties and structure of aluminum hydrochloride obtained from aluminum isopropanolane]. / Badanie wlasciwosci fizykochemicznych i przemian fazowych zeli wodorotlenku glinowego otrzymanego z izopropanolanu glinu.

Aluminium hydroxide gels were precipitated from aluminium isopropoxide by addition of water or aqueous solutions of Na2SO4, NaCl and NaNO3. The antacid activity of the gels was assessed on the basis of determinations of their total capacity to neutralize HCl, while structure of the gels was studied by X-ray diffraction analysis and IR spectrometry. It has been stated that prolonged storage, higher storage temperature and presence of water promote conversion of the active form of aluminium hydroxide gels in pharmaceutical preparations into less active forms.

[Comparison of the methods of in vitro evaluation of the neutralizing properties of drugs from the antacid group]. / Porównanie metod oceny in vitro wlasciwosci zobojetniajacych preparatów z grupy antacida.

Usefulness of the pH-stat method for assaying the neutralizing activity of antacids was compared with the ones of the methods based on the determination of the action time by dynamic methods. A high level of correlation between the antacid dose and the neutralization capacity has been stated. The found relationships proved to enable optimization of the antacid dosage as well as prediction of the therapeutic effect.

Studies of neutralizing properties of antacid preparations. Part 4: Application of Weibull distribution function to neutralization of dihydroxyaluminum sodium carbonate.

The rate of neutralization of hydrochlorid acid by dihydroxyaluminum sodium carbonate (DHASC) has been studied by pH-stat method. The neutralization process was examined by monitoring the appearance of aluminum and sodium ions in the reaction medium. The Weibull distribution function was applied to the quantitative interpretation of neutralization rate data. All mathematically meaningful parameters derived from this distribution function were useful for consideration of the mechanism according to which the neutralization of DHASC occurs.

Studies of neutralizing properties of antacid preparations. Part 3: Constant pH neutralization of hydrochloric acid by hydrotalcite.

The neutralization reaction of hydrochloric acid by powdered hydrotalcite (HT) was studied by pH-stat method in the range of pH from 3.0 to 4.8. The neutralization process was examined by monitoring the appearance of aluminium and magnesium ions in the reaction medium, by determination of the chloride concentration in solution and by IR analysis of partially neutralized HT. The mechanism of acid neutralization of HT is discussed.

Effect of composition on the neutralizing properties of antacid preparations.

11 antacid mixtures made up to simulate the preparations available on the market were prepared. These mixtures contain aluminium hydroxide gel, calcium carbonate, magnesium hydroxide and magnesium trisilicate. The antacid properties of the mixtures obtained were characterized by total acid consuming capacity, rate of neutralization and duration of action. It was indicated that the composition of the mixtures influenced their neutralizing properties; an interaction between constituents of these preparations was noted.

Preparation of drugs used in hyperacidity. Part IV. Effect of sulphate, chloride and nitrate ions and mannitol on neutralizing properties and changes of alumina gels.

The stability of alumina gels precipitated from the appropriate aluminum salts with ammonia solution have been investigated. The effect of SO42-, Cl-, NO3-ions and mannitol on this stability was evaluated. SO42-ions, and to a lesser degree also Cl- and NO3-ions stabilize alumina gel due to the incorporation in its structure. The use of mannitol solution as a suspension medium results also in the complete stabilization of the gel.

Preparation of drugs used in hyperacidity. Part III. Stability of alumina gels.

The effect of temperature on the stability of alumina gels heated in the solid state and in the suspension was investigated. The suspensions were made in water, 1,4-dioxane and their mixture. It was found that the ageing of gels occurs during heating them in the solid state, in water and water-dioxane mixture as a first order reaction. The neutralizing properties of gel heated in 100% dioxane were not changed. The phase analysis of the investigated preparations was based on X-ray measurements. The contribution of water in the mechanism of gel changes is discussed.

Preparation of drugs used in hyperacidity. Part I. Effects of pH of precipitation on the neutralizing properties of alumina gels.

Alumina gels were obtained from sodium aluminate by addition of 3 N HNO3, HCl or H2SO4 solutions or by saturation with gaseous CO2. The effect of several physicochemical factors (pH of precipitation, kind and concentration of precipitating agent, temperature) on the neutralizing properties of the obtained forms of Al(OH)3 was investigated. The linear correlation between the pH of precipitation and the neutralizing properties was found. The effect of different precipitating anions on the acid-consuming capacity and the rate of neutralization of 0-1 N HCl was established.