Comparative bioavailability of two tablet formulations of ranitidine hydrochloride in healthy volunteers.

This investigation was carried out to evaluate the bioavailability of a new tablet formulation of ranitidine HCl (300 mg), Ranid, relative to the reference product, Zantac, (300 mg) tablets. The bioavailability was carried out on 24 healthy male volunteers who received a single dose (300 mg) of the test (T) and the reference (R) products in the fasting state, in a randomized balanced 2-way crossover design. After dosing, serial blood samples were collected for a period of 16 hours. Plasma harvested from blood was analyzed for ranitidine by a sensitive and validated high-performance liquid chromatographic assay. The maximum plasma concentration (Cmax), area under the plasma concentration time curve up to the last measurable concentration (AUC0-t), and to infinity (AUC0-infinity) and the absorption rate (Cmax/AUC0-infinity) were analyzed statistically under the assumption of a multiplicative model. The time to maximum concentration (Tmax) was analyzed assuming an additive model. The parametric confidence intervals (90%) of the mean values of the pharmacokinetic characteristics (AUC0-t, AUC0-infinity), Cmax and Cmax/AUC0-infinity) for T/R ratio were in each case well within the bioequivalence acceptable range of 80-125%. The test formulation was found bioequivalent to the reference formulation by the Schuirmann's two one-sided t-tests and by Wilcoxon Mann Whitney two one-sided tests procedure. Therefore, the 2 formulations were considered to be bioequivalent.

Comparative bioavailability of two tablet formulations of acyclovir in healthy volunteers.

This investigation was carried out to evaluate the bioavailability of a new tablet formulation of acyclovir (400 mg), Clovir, relative to reference product, Zovirax (400 mg) tablets. The 2 brands were found to be similar in weight variation, disintegration time, dissolution, and assay as stipulated by the USPXXIII, as well as by the manufacturer. The bioavailability was carried out on 24 healthy male volunteers who received a single dose (400 mg) of the test (T) and the reference (R) products in the fasting state, in a randomized balanced 2-way crossover design. After dosing, serial blood samples were collected for a period of 16 hours. Plasma harvested from blood was analyzed for acyclovir by a sensitive and validated high-performance liquid chromatographic assay. The maximum plasma concentration (Cmax), area under the plasma concentration-time curve up to the last measurable concentration (AUC0-t), and to infinity (AUC0-infinity), and the absorption rate (Cmax/AUC0-infinity) were analyzed statistically under the assumption of a multiplicative model. The time to maximum concentration (Tmax) was analyzed assuming an additive model. The parametric confidence intervals (90%) of the mean values of the pharmacokinetic characteristics (AUC0-t, AUC0-infinity, Cmax, Cmax/AUC0-infinity) for T/R ratio were in each case, well within the bioequivalence acceptable range of 80-125%. The test formulation was found bioequivalent to the reference formulation by the Schuirmann's two 1-sided t tests and by Wilcoxon Mann Whitney two 1-sided tests procedure. Therefore, the 2 formulations were considered to be bioequivalent.

Formulation and in vitro and in vivo availability of diclofenac sodium enteric-coated beads.

Diclofenac sodium enteric-coated beads were prepared using the conventional pan coating technique. Eudragit L100 was used as a pH-dependent release-controlling polymer. The beads were evaluated for their particle size distribution, drug loading efficiency, flowability, in vitro release in 0.1 N HCl (pH 1.2) and phosphate buffer (pH 6.8), and bioavailability in beagle dogs relative to the commercial enteric-coated tablets Voltaren. The beads showed a narrow particle size distribution in which 83% of the beads were in the range of 1-2 mm. The actual yield of the beads was 90.5% and their drug loading was 92%. The beads released about 8% of the drug during 2 hr of dissolution in 0.1 N HCl, and the commercial tablets released no drug. In phosphate buffer (pH 6.8) both formulations released their drug content in 1 hr. Both formulations are, therefore, in compliance with the USP requirements for release from enteric-coated dosage forms. The in vivo availability study in six beagle dogs revealed that the formulated enteric-coated beads filled in hard gelatin capsules had a 197.54% bioavailability relative to that of the commercial Voltaren tablets. The tablets showed a significantly lower (p < 0.05) area under curve for 0-8 hr (AUC0-8 hr) of 13.44 +/- 15.02 micrograms hr/ml compared to 26.55 +/- 5.19 micrograms hr/ml for the capsules. The capsules showed a nonsignificantly (p > 0.05) higher peak plasma concentration (Cmax) of 6.77 +/- 0.67 micrograms/ml compared to 5.88 +/- 7.38 micrograms/ml for the tablets. The time to reach peak (Tmax) values were 2 +/- 1.48 and 2.25 +/- 1.08 hr for the capsules and tablets, respectively. The capsules showed less interdog variability with respect to Cmax (CV% 34.6) and AUC (CV% 19.55) compared to CV% 79.9 and 111.76, respectively, for the commercial tablets.

Comparative bioavailability of two tablet formulations of ibuprofen.

This investigation was carried out to evaluate the bioavailability of a new tablet formulation of ibuprofen (600 mg), Profinal, relative to reference product, Brufen (600 mg) tablets. The 2 brands were found to be similar in assay, weight variation and dissolution as stipulated by the USP XXII, as well as the disintegration time, as specified by the BP 1988. The bioavailability was carried out on 18 healthy male volunteers who received a single dose (600 mg) of the test (T) and the reference (R) products in the fasting state, in a randomized balanced 2-way crossover design. After dosing, serial blood samples were collected for a period of 12 hours. Plasma harvested from blood was analyzed for ibuprofen by a sensitive and validated high-performance liquid chromatographic assay. The maximum plasma concentration (Cmax), area under the plasma concentration-curve up to the last measurable concentration (AUC0-t), and to infinity (AUC0-infinity) were analyzed statistically under the assumption of a multiplicative model. The time to maximum concentration (Tmax) was analyzed assuming an additive model. The parametric confidence intervals (90%) of the mean values of the pharmacokinetic characteristics (AUC0-t, AUC0-infinity and Cmax) for T:R ratio were in each case, well within the bioequivalence acceptable range of 80-125%. The test formulation was found bioequivalent to the reference formulation by the Schuirmann's 2 1-sided t-tests and by Wilcoxon-Mann-Whitney 2 1-sided tests procedure. Therefore, the 2 formulations were considered to be bioequivalent.

Comparative bioavailability of two tablet formulations of metoclopramide hydrochloride.

This investigation was carried out to evaluate the bioavailability of a new tablet formulation of metoclopramide hydrochloride (10 mg), Metosil relative to a recognized product, Plasil BP. The two brands were found to be similar in assay and content uniformity and both met the BP requirements of disintegration time. The bioavailability was carried out on 18 healthy male volunteers who received a single dose (2 x 10 mg) of the test (T) and the recognized (R) products in a randomized balanced 2-way crossover design. After dosing, serial blood samples were collected for a period of 8 hours. Plasma harvested from blood was analyzed for metoclopramide by a sensitive and validated high-performance liquid chromatographic assay. The maximum plasma concentration (Cmax), area under the plasma concentration curve up to the last measurable concentration (AUC0-t), and to infinity (AUC0-00) were analyzed statistically under the assumption of a multiplicative model. The time to maximum concentration (Tmax) was analyzed assuming an additive model. The parametric confidence intervals (90%) of the mean values of the pharmacokinetic characteristics (AUC0-t AUC0-00 and Cmax) for T:R ratio were in each case well within the bioequivalence acceptable range of 0.8-1.25. The test formulation was found bioequivalent to the reference formulation by the Schuirmann's 2 one-sided t-tests and by Wilcoxon-Mann-Whitney 2 one-sided tests procedure. Therefore, the two formulations were considered to be bioequivalent.

The effect of colestipol and cholestyramine on ibuprofen bioavailability in man.

The purpose of this study was to determine whether a concomitant single oral dose of one of the anion exchange resins colestipol hydrochloride (10 g) or cholestyramine (8 g) administered with ibuprofen (400 mg) would alter the bioavailability of this non-steroidal anti-inflammatory agent. The study was performed according to a randomized three-way crossover design in six healthy male volunteers. After dosing, serial blood samples were collected for a period of 10 h. Plasma harvested from blood was analysed for ibuprofen by a sensitive high-performance liquid chromatographic method. There were no significant differences between colestipol treatment and control for peak plasma concentration (Cmax), time to peak concentration (Tmax), area under the plasma concentration-time curve (AUC), mean residence time (MRT), elimination rate constant (Kel), or elimination half-life (t1/2). Cholestyramine treatment resulted in a significant decrease in AUC (26%, p < 0.05) and Cmax (34.4%, p < 0.01) and a significant increase in Tmax (80%, p < 0.01) and MRT (20.2%, p < 0.05). Cholestyramine administration showed no significant effect on the Kel and t1/2 values. A significant correlation was obtained between the increase in MRT and the increase in Tmax. The confidence intervals (90%) of the mean values of the pharmacokinetic parameters (AUC0-infinity and Cmax) for the colestipol: control ratio were well within the acceptable range of 100 +/- 20, whereas those for the cholestyramine: control ratio were outside it. Colestipol treatment was found to be bioequivalent to the control treatment by Schuirmann's two one-sided t tests, while cholestyramine treatment was found to be bioinequivalent.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of cholestyramine and colestipol on the absorption of diclofenac in man.

The effect of oral administration of the non-absorbable anion-exchange resins cholestyramine and colestipol hydrochloride on the absorption of diclofenac in man was studied. Adsorption studies in vitro were also performed. In a randomized crossover study consisting of three phases, single doses of water suspensions of colestipol hydrochloride (10 g), or cholestyramine (8 g), or water only were given to six healthy male volunteers immediately following ingestion of diclofenac (100 mg). After dosing, serial blood samples were collected for a period of 8 hours. Plasma harvested from blood was analyzed for diclofenac by a sensitive and accurate high-performance liquid chromatographic method. The area under the plasma concentration-time curve was moderately (33%, p < 0.05) reduced by colestipol, and greatly reduced (62%) by cholestyramine. The maximum plasma concentration was reduced (58%) by colestipol and even more (75%) by cholestyramine treatment. The in-vitro adsorption studies showed that colestipol has a weaker capacity for adsorption of diclofenac compared to cholestyramine. The in-vivo data suggest a reduction of diclofenac bioavailability when colestipol or cholestyramine is administered concomitantly.

The effect of colestipol and cholestyramine on the systemic clearance of intravenous ibuprofen in rabbits.

The effect of oral administration of the non-absorbable anion-exchange resins cholestyramine and colestipol on the systemic clearance and other pharmacokinetic parameters of intravenously administered ibuprofen (25 mg kg-1) was studied in rabbits. Single doses of colestipol hydrochloride (0.4 g kg-1) or cholestyramine (0.17 g kg-1) were given 30 min before ibuprofen administration. In cholestyramine-treated rabbits a significant reduction in ibuprofen plasma concentration was observed compared with both control (water only) and colestipol-treated rabbits. Cholestyramine treatment resulted in a significant decrease in the terminal elimination half-life and the mean residence time. Furthermore, a 31% increase in the systemic clearance and 23% decrease in the area under the plasma concentration-time curve were also observed in cholestyramine-treated rabbits. Colestipol treatment did not change these parameters. The volume of distribution parameters (Vdss and Vd(area)) did not change following either treatment. The changes in the pharmacokinetic parameters are compatible with an acceleration of ibuprofen elimination induced by oral administration of cholestyramine and not by colestipol. This effect is thought to be due to augmentation of net biliary excretion through enteric binding.

Phenobarbital solubility in propylene glycol-glycerol-water systems.

Phenobarbital solubility in various binary and ternary propylene glycol-glycerol-water solvent systems was determined. Phenobarbital concentrations several times those of the ethanol-containing USP and BPC elixirs were obtained. From log solubility-solvent composition plots, a general equation was developed for phenobarbital solubility prediction in propylene glycol-water, glycerol-water, and propylene glycol-glycerol-water solvent systems. Solubility predictions using another equation, based on linear log solubility-dielectric constant relationships, were limited by the need to use different constants for different solvent blends. Heats of solution for phenobarbital determined in selected solvent blends as well as in USP and BPC elixirs varied within a very narrow range, suggesting similar solute-solvent interactions.

Effect of concomitant administration of magnesium trisilicate on GI absorption of dexamethasone in humans.

The oral absorption of dexamethasone in humans was compared to its absorption when coadministered with magnesium trisilicate. The bioavailability of dexamethasone was estimated by measuring the suppressive effect of the drug on the daily excretion of endogenous steroids. Administration of 1 mg of dexamethasone to six healthy male volunteers significantly decreased the urinary excretion of 11-hydroxycorticosteroids. However, the coadministration of magnesium trisilicate with dexamethasone decreased its absorption, as indicated by the increased urinary excretion of 11-hydroxycorticosteroids. The decrease in absorption was attributed to drug adsorption on the antacid surface. These results confirm previous in vitro findings.

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.

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.

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.

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.

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.

Inhibitory effect of dioctyl sodium sulfosuccinate on trypsin activity.

The inhibitory effect of dioctyl sodium sulfosuccinate on the proteolytic activity of trypsin was investigate over the pH 6-8 range. The antitryptic activity was determined using two different substrates: casein and N,alpha-benzoyl-DL-arginine-p-nitroanilide hydrochloride. The mechanistic studies revealed the substrate-inhibitor interaction to be the overall major mechanism of inhibition. This interaction was shown to involve substrate depletion, probably involving some primary sites of the natural substrate casein. Some inhibition was also shown to be due to an interaction between the enzyme and the inhibitior molecules. The interactions of the inhibitor with the enzyme and the substrate were irreversible. The possible therapeutic significance of the inhibitory effect of the surfactant is discussed.

Effect of surfactants on absorption through membranes III: effects of dioctyl sodium sulfosuccinate and poloxalene on absorption of a poorly absorbable drug, phenolsulfonphthalein, in rats.

The influence of dioctyl sodium sulfosuccinate and poloxalene on the GI absorption of phenolsulfonphthalein in the rat was studied. Urinary excretion data after oral administration of the drug to intact rats and loss of the drug from the whole small intestine as a loop were both utilized to assess the effect of the surfactants on absorption. Dioctyl sodium sulfosuccinate markedly increased the absorption of the drug, and the extent was dependent on the surfactant concentration. Maximum effect was observed at the reported ED50 in rats, of the surfactant as a fecal softener. The mechanism responsible for absorption enhancement seems to be an alteration of the permeability of the intestinal membrane. Micellar complexation between the drug and the surfactant resulted in a lesser increase in absorption at the higher surfactant concentrations. Poloxalene did not increase drug absorption, but higher concentrations caused a decrease in absorption due to micellar entrapments of the drug molecules. The influence of dioctyl sodium sulfosuccinate on the peritoneal absorption of the drug was also investigated. Lower doses of the surfactant increased absorption of the drug by altering the membrane permeability. Higher doses decreased absorption due to unavailability of the drug molecules entrapped in the micelles.

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.