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Biomedical subjects

S A Khalil

Publications and source records attributed to S A Khalil.

At least 37 records · Page 2Linked to original sources
PubMed1978

The in vitro adsorption of some antiepileptics on antacids.

The adsorption of the antiepileptics sulthiame, phenytoin, mephenytoin, mesuximide, phensuximide, ethosuximide, and primidone on various antacids or adsorbents was studied at 37 degrees C. The antacids or adsorbents used were magnesium trisilicate, aluminium hydroxide, bismuth oxidcarbonate, magnesium oxide, talc, kaolin and calcium carbonate. Magnesium trisilicate was found to be the strongest adsorbent for most of the antiepileptics tested. The other antacids or adsorbents were without an appreciable effect. Sulthiame exhibited the highest degree of interaction with magnesium trisilicate. Mesuximide, phensuximide and primidone showed intermediate adsorption properties. Mephenytoin and phenytoin had lower adsorption characters, while ethosuximide was the least adsorbed antiepileptic tested. The extent of elution was found to be inversely proportional to adsorption. Alkaline solution gave relatively higher eluting power than acid solution. The mechanism of adsorption of the various antiepileptics on antacids was discussed. The effect of magnesium trisilicate on the bioavailability of coadministered antiepileptics has still to be confirmed by in vivo testing.

Adsorption↗
PubMed1977

Effect of chloroquine adsorption on acid reactivity of magnesium trisilicate.

Due to the adsorption of chloroquine by magnesium trisilicate, both the BP acid absorption test and the rate of hydrochloric acid uptake, as monitored by pH measurements, were significantly reduced. This reduction was dependent on the amount of chloroquine adsorbed, since multilayer adsorption produced relatively more suppressive effects than did monolayer adsorption. The presence of adsorbed chloroquine also decreased the amounts of magnesium released in an acid medium. The inhibition of the antacid property due to chloroquine adsorption may be attributed to the occupation of the reactive sites of the antacid surface by chloroquine and to a reduction of the surface of the antacid due to flocculation of the particles.

Adsorption↗
PubMed1977

Effect of surfactants on absorption through membranes V: Concentration-dependent effect of a bile salt (sodium deoxycholate) on absorption of a poorly absorbable drug, phenolsulfonphthalein, in humans.

The effect of administration of 600-and 300-mg doses of sodium deoxycholate 1 hr before phenolsulfonphthalein solution is reported. The 600-mg dose caused a decrease in drug bioavailability as measured by the total amount excreted in 24 hr. The 300-mg dose cause and increase in the initial phenolsulfonphthalein absorption rate, suggesting a direct action of the bile salt on membrane permeability. The decrease in absorption upon administration of 600 mg was attributed to micellar entrapment of the drug molecule.

Adult↗
PubMed1977

In vitro adsorption of some corticosteroids on antacids.

The adsorption of prednisone, prednisolone, fluprednisolone, betamethasone, triamcinolone, beta-methylprednisone acetate and hydrocortisone acetate on various antacids or adsorbents was studied at 37 degrees C. The antacids or adsorbents used were magnesium trisilicate, aluminum hydroxide, bismuth oxycarbonate, magnesium oxide, magnesium carbonate, calcium carbonate, talc, kaolin and charcoal. Magnesium trisilicate and charcoal had the highest adsorption capacity for the corticosteroids tested. Bismuth oxycarbonate and talc had intermediate adsorption properties while kaolin and aluminium hydroxide had lower effects. Other antacids were without any adsorption character. Results of the elution study confirmed the higher affinity of magnesium trisilicate over that of bismuth oxycarbonate and talc for the steroids tested. Further in vivo testings are still needed to assess the effect of antacids on the bioavailability of coadministered corticosteroids.

Adrenal Cortex Hormones↗
PubMed1976

Effect of dioctyl sodium sulfosuccinate and poloxamer 188 on dissolution and intestinal absorption of sulfadiazine and sulfisoxazole in rats.

The influence of two medicinal surfactants, poloxamer 188 and dioctyl sodium sulfosuccinate, on the dissolution of sulfisoxazole and sulfadiazine was investigated. A dramatic increase in the dissolution rate was observed at all surfactant concentrations. Drug absorption from the rat small intestine was also studied, and a significant but less dramatic increase was noted. Dissolution rate and absorption could be correlated only qualitatively. The two surfactants had no effect on the amount of sulfisoxazole excreted by the rat in 24 hr.

Animals↗
PubMed1976

Determination of hyoscyamine in BPC mixtures.

The hyoscyamine contents of four BPC mixtures (containing either belladonna or hyoscyamus tincture) were determined using the acid-dye technique. A sample size of 10 ml was required. The mean percentage recovery of hyoscyamine ranged from 99.73 to 101.03 from three mixtures; from the magnesium trisilicate and belladonna mixture, it was 94.8. The effects of pH and adsorption on the extraction of the alkaloid-dye complex from the mixtures examined are discussed.

Aluminum Hydroxide↗
PubMed1976

Inhibitory effect of dioctyl sodium sulfosuccinate on pepsin activity.

The inhibitory effect of dioctyl sodium sulfosuccinate of hog pepsin activity was investigated over the pH 1.5-3.0 range. The inhibitory effect was studied using a natural substrate, hemoglobin, and a synthetic substrate, N-acetyl-L-phenylalanyl-L-diiodotyrosine. The mechanistic studies revealed that a substrate-inhibitor interaction was the major mechanism of inhibition with hemoglobin. However, some direct enzyme inhibition also was involved. With the synthetic substrate, the inhibition was due to a competition between the substrate and inhibitor molecules for the enzyme. The possible therapeutic significance of the inhibitory effect of the medicinal surfactant is discussed.

Octanols↗
PubMed1976

Dissolution characteristics and oral absorption of digitoxin and digoxin coprecipitates.

A marked increase in the dissolution rates od digitoxin and digoxin was attained by dispersing the drugs in two inert solid carriers, poloxamer 188 and deoxycholic acid. The 1 and 10% (w/w) drug-carrier solid dispersions were prepared by the solvent method. The former dissolved significantly faster than the latter. The oral administration of 10% (w/w) digitoxin-carrier coprecipitates to mice significantly increased toxicity. This observed increase is attributed to an increase in the rate and, possibly, the extent of oral absorption of the drug. Although a 10% coprecipitate of digoxin in both carriers showed an increase in the dissolution rate, no increase in oral toxicity was observed. X-ray diffraction patterns indicated that both digitoxin and deoxycholic acid undergo crystalline modifications due to treatment by the solvent, but the exact nature of the drug-carrier solid dispersions was not revealed.

Animals↗
PubMed1976

The effect of some additives on the adsorption of tetracycline hydrochloride on magnesium trisilicate and milk.

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.

Adjuvants, Pharmaceutic↗
PubMed1976

The in vitro adsorption of some antibiotics on antacids.

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.

Adsorption↗
PubMed1976

The in-vitro adsorption of some antirheumatics on antacids.

The adsorption of sodium salicylate, salicylamide, acetylsalicylic acid, paracetamol, mefenamic acid, flufenamic acid, phenylbutazone, oxyphenbutazone, phenazone, aminophenazone, indometacin and methiazinic acid on some antacids was studied. The antacids used were magnesium trisilicate, magnesium oxide, aluminium hydroxide, bismuth oxycarbonate, calcium carbonate and kaolin. Magnesium oxide, followed by aluminium hydroxide and bismuth oxycarbonate showed a fairly high adsorptive capacity for salicylates, mefenamic acid, flufenamic acid, methiazinic acid, indometacin and to a lesser extent for phenylbutazone and oxyphenbutazone. On the other hand, magnesium trisilicate exhibited a tendency to adsorb phenazone, aminophenazone, indometacin and methiazinic acid. Kaolin was found to be a good adsorbent for anthranilic acid derivatives, indometacin and methiazinic acid. Calcium carbonate showed a weak adsorptive capacity for all drugs tested. The adsorption of phenylbutazone and salicylates on magnesium oxide, aluminium hydroxide and/or bismuth oxycarbonate obeyed the Freundlich adsorption isotherm. Elution study showed that salicylates and anthranilic acid derivatives were tenaciously held by magnesium oxide while magnesium trisilicate showed an intermediate retention power for phenazone and aminophenazone. Sodium hydrogen carbonate solution gave, in general, a higher eluting power than hydrochloric acid solution. A marked reduction in the apparent partition coefficients of all drugs tested was observed in the presence of magnesium trisilicate or aluminium hydroxide. Careful in vitro and in vivo testing of drug availability is advisable prior to the concomitant administration of antirheumatics with antacids or other adsorbents.

Adsorption↗
PubMed1975

Effect of surfactants on absorption through membranes IV: effects of dioctyl sodium sulfosuccinate on absorption of a poorly absorbable drug, phenolsulfonphthalein, in humans.

To explore the effect of dioctyl sodium sulfosuccinate on drug absorption in humans, the urinary excretion of a poorly absorbable drug, phenolsulfonphthalein, administered in solution with and without the surfactant was determined. Coadministration of a therapeutic dose of the surfactant with the drug solution resulted in a significant increase in the initial rate of absorption. A small increase in the extent of absorption was also observed. Pretreatment with the surfactant for 6 nights, followed by administration of the drug on the 7th day, did not significantly change the rate of extent of absorption. The surfactant is thought to have a direct effect on the GI membrane, resulting in a temporary change in its permeability. This effect appears to be reversible after a few hours.

Adult↗
PubMed1975

Succinylsulfathiazole crystal forms. II: Effect of additives on kinetics of interconversion.

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.

Chemical Phenomena↗
PubMed1975

Succinylsulfathiazole crystal forms. III: Crystal growth studies.

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.

Chemical Phenomena↗