RESUMEN
The adsorption of oxytetracycline hydrochloride, tetracycline hydrochloride, doxycycline hyclate, triacetyloleandomycin, chloramphenicol, ampicillin, and cloxacillin sodium was studied on various antacids namely, magnesium trisilicate, magnesium oxide, calcium carbonate, bismuth oxycarbonate, aluminium hydroxide, and kaolin. The adsorption of the various antibiotics by milk was also tested as milk is frequently used as an antacid. Charcoal was included in the present study as a model adsorbent having a large hydrophobic surface. The adsorption of the various antibiotics on the different antacids and other adsorbents in most cases obeyed the Freundlich adsorption isotherm. Magnesium trisilicate and magnesium oxide showed the highest adsorptive capacity, relative to other antacids used, for most antibiotics. Calcium carbonate and aluminium hydroxide and intermediate power while kaolin and bismuth oxycarbonate had the least adsorptive power. Charcoal exhibited a marked adsorption for all antibiotics tested. Tetracyclines were found to be more highly adsorbed than other antibiotics studied. Triacetyloleandomycin and chloramphenicol had intermediate values. Ampicillin was only adsorbed to a slight extent while cloxacillin was not adsorbed on the antacids used. The extent of adsorption was correlated to the structure of both the adsorbent and adsorbate, the pH of the adsorbent suspension, and to the polarity of the antibiotic in such pH. The reversibility of the adsorption process was studied in different media and at pH values similar to those of the gastrointestinal tract. The extent of elution was found to be inversely proportional to the adsorptive capacity of the different adsorbents. In general, 0.0143 n NaHCO3 solution was found to possess higher eluting properties than 0.01 n HCl. An exception to this pattern was observed with tetracyclines adsorbed on aluminium hydroxide where the elution with acid resulted in a higher degree of desorption. Careful in vitro and in vivo testing of drug availability is advisable prior to the concomitant administration of antibiotics with antacids or other adsorbents.
Asunto(s)
Antiácidos , Antibacterianos , Adsorción , Animales , Carbón Orgánico , Química Farmacéutica , Concentración de Iones de Hidrógeno , Leche , Temperatura , TermodinámicaRESUMEN
The effect of various additives on the adsorption of tetracycline hydrochloride on magnesium trisilicate or milk was investigated. Adsorption-elution, dialysis and sedimentation volume measurements were used in the present investigation. Citric acid was found to exert the highest adsorption suppressing effect of the antibiotic on both antacids. The nonionic surfactants, polyoxyethylene-23-lauryl ether (Brij 35) and polysorbate 80, had an intermediate action, while polyethylene glycol 6000 (PEG-6000), polyvinylpyrrolidone (PVP), sodium carboxymethylcellulose (CMC) and urea had only a slight effect. On the other hand, the effect of sodium benzoate and sodium salicylate varied with concentration. Results of the elution study showed that the efficiency of the additives, as eluting agents, was more or less parallel with their influence on adsorption. The presence of citrate or Brij 35, having the highest adsorption-suppressing effect, was found to have a negligible effect on the chemical stability or microbiological activity of tetracycline. Conclusions were made that the incorporation of some of these additives may possibly reduce tetracycline-antacids interactions and consequently improve the antibiotic availability when co-administered with antacids.
Asunto(s)
Magnesio , Leche , Ácido Silícico , Dióxido de Silicio , Tetraciclina , Adyuvantes Farmacéuticos , Adsorción , Animales , Benzoatos , Citratos , Diálisis , Polímeros , Salicilatos , Tensoactivos , Temperatura , UreaRESUMEN
The effect of various additives on the rate of transformation of the metastable anhydrous succinylsulfathiazole Form I to the water-stable dihydrate Form II in aqueous suspensions was studied. Some structurally related compounds, viscosity-imparting agents, surfactants, and coloring agents were used as possible transformation retardants. The effect of including seeds of Form II in the presence and absence of additives is also discussed. Some additives, e.g., methylcellulose and phthalysulfathiazole, showed significant transformation-retarding effects. Other additives, e.g., sulfanilamide and glycerin, increased the rate of transformation. Coloring agents had only slight effects. Utilization of the results in the formulation of physically stable aqueous suspensions of succinylsulfathiazole is discussed.
Asunto(s)
Sulfatiazoles , Fenómenos Químicos , Química Física , Colorantes , Cristalización , Cinética , Succinatos , Tensoactivos , Suspensiones , Temperatura , ViscosidadRESUMEN
Crystal growth accompanying the transformation of succinylsulfathiazole crystal forms in aqueous suspensions was studied using a projecting microscope. The effects of increase of temperature, agitation, inclusion of seeds of Form II (the water-stable dihydrate), sulfathiazole, methylcellulose, and polysorbate 80 on the particle-size distribution of anhydrous succinylsulfathiazole Form I were examined. Rates of crystal growth, calculated as increase of diameter per unit time, were given under different experimental conditions. Increase of temperature, agitation, and seeding with nuclei of Form II had significant growth-accelerating effects. Sulfathiazole and polysorbate 80 had growth-retarding effects. Methylcellulose inhibited the crystal growth of Form I for over a year. Aqueous suspensions of Form II did not show any change in particle-size distribution. The crystal growth was shown to be a direct consequence of the transformation of the crystal form. Physical conditions and additives which had accelerating or retarding effects on the rate of succinylsulfathiazole in aqueous suspensions.