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At least 1,063 records · Page 59Linked to original sources
PubMed1979

Analysis of fludrocortisone acetate and its solid dosage forms by high-performance liquid chromatography.

A newly developed reversed-phase high-performance liquid chromatographic assay and test method for determining content uniformity are described for fludrocortisone acetate. The method is stability indicating and separates most known degradation products and impurities. In addition, the method is simple, sensitive, accurate, and relatively free of interferences. The coefficient of variation for multiple weight assays is between 0.3 and 1.8%.

Chromatography, High Pressure Liquid↗
PubMed1980

Dosage form design for improvement of bioavailability of levodopa II: bioavailability of marketed levodopa preparations in dogs and parkinsonian patients.

To estimate the absolute bioavailability of oral levodopa, plasma concentrations and urinary excretion of levodopa and its metabolites were determined in beagle dogs and in parkinsonian patients after intravenous and oral drug administration. The absolute bioavailability of orally administered levodopa was estimated to be about 35% in both dogs and patients; however, the total amount absorbed of intact drug and levodopa metabolites was estimated to be 80--90% of the administered dose. Due to the similarities of the pharmacokinetic characteristics of levodopa found in beagle dogs and in humans, beagle dogs can serve as a model to study bioavailability, absorption, and metabolic mechanisms.

Administration, Oral↗
PubMed1980

High-pressure liquid chromatographic analysis of pramoxine hydrochloride in high lipoid aerosol foam dosage form.

A rapid and quantitative method for the determination of pramoxine hydrochloride by high-pressure liquid chromatography is presented. The drug is extracted as the salt from a preparation with a high lipoid composition by partitioning it to the aqueous phase of an ether-methanol-water-acetic acid system. The extract is chromatographed on an octadecylsilane bonded packing with a methanol-water-acetic acid-methanesulfonic acid mobile phase. The time required for each separation is approximately 6 min. Analytical recoveries of 100.4 +/- 1.5% were obtained.

Aerosols↗
PubMed1980

Evaluation of sustained-action chlorpheniramine-pseudoephedrine dosage form in humans.

This investigation compared the bioavailability of chlorpheniramine and pseudoephedrine from a sustained-action capsule and a combination of two reference standard tablets in 24 normal human subjects. The capsule contained 8 mg of chlorpheniramine maleate and 120 mg of pseudoephedrine hydrochloride, and the tablets each contained half of the amount of the chlorpheniramine or pseudoephedrine in the capsule. Because the capsule was a combination product, a new study design had to be developed to accommodate steady-state conditions for both drugs. Each subject received the capsule (every 12 hr) and the combination of the reference tablets (every 6 hr) for 8 days according to a two-way crossover design. Serial blood and urine samples were taken during the entire study. Plasma and urine samples were assayed for chlorpheniramine and pseudoephedrine by sensitive and specific high-pressure liquid chromatographic or GLC methods. There were no significant differences in the plasma concentration profiles of chlorpheniramine and pseudoephedrine at all times, except when the capsule developed peaks or the tablets developed nadirs. The highest mean peak plasma concentrations for the capsule and the tablets were 38.7 and 32.9 ng of chlorpheniramine/,ml and 525 and 515 ng of pseudoephedrine/ml, respectively. The mean biological half-lives of chlorpheniramine and pseudoephedrine were 21.6 and 8.0 hr, respectively. The AUC and unchanged drug excreted in urine, after a single dose and at steady state, showed that the sustained-action capsule (given every 12 hr) and the reference standard tablets (given every 6 hr) were bioequivalent.

Adult↗
PubMed1980

High-performance liquid chromatographic assay of codeine in acetaminophen with codeine dosage forms.

An accurate, rapid, and specific high-performance liquid chromatographic (HPLC) assay was developed for codeine in acetaminophen with codeine combination products. The internal standard (chlorpheniramine maleate), codeine, acetaminophen, and several other test compounds or impurities were well separated. A complete analysis took < 10 min. The relative standard deviations of the retention time, precision, and accuracy were 0.5, 0.4, and 0.5%, respectively. An excellent linear correlation was obtained between the HPLC and GLC methods.

Acetaminophen↗
PubMed1980

Dosage form design for improvement of bioavailability of levodopa III: Influence of dose on pharmacokinetic behavior of levodopa in dogs and Parkinsonian patients.

The relationship between the dose of levodopa and its pharmacokinetic behavior following intravenous and oral administration was investigated in dogs and parkinsonian patients. Six beagle dogs received single doses of 2.4, 4.8, and 9.6 mg of levodopa/kg iv and single doses of 4.8, 9.6, and 19.2 mg of levodopa/kg po in a crossover fashion on separate occasions. Three parkinsonian patients received single oral doses of approximately 3.8, 7.7, and 15.4 mg of levodopa/kg in a crossover test. Plasma samples were analyzed for intact levodopa and total dopamine. The relationship between the area under the plasma concentration-time curve (AUC) of levodopa and the intravenous dose to dogs was linear. However, in both dogs and patients, the relationship after oral dosing was nonlinear, with the relative AUC increasing with increasing dose. Therefore, the pharmacokinetic behavior of levodopa after oral administration to dogs and patients was dose dependent.

Administration, Oral↗
PubMed1980

Nasal absorption of propranolol from different dosage forms by rats and dogs.

The blood levels of propranolol in rats and dogs were compared after the administration of nasal, intravenous, and oral solutions. The results indicate that the blood drug levels after nasal and intravenous administration were identical, but the oral administration resulted in considerably lower blood levels. Sustained-release formulations of the drug also were administered nasally and resulted in low initial but prolonged blood levels. The bioavailability of the sustained-release formulation was identical to that of the intravenous administration.

Absorption↗
PubMed1981

Chlorothiazide absorption from solution and tablet dosage forms in dogs.

The bioavailability of an aqueous solution of chlorothiazide and three commercially available chlorothiazide tablets was assessed in adult mongrel dogs. In two crossover urinary excretion studies, six fasting dogs received single 500-mg doses of chlorothiazide as an aqueous solution, one 500-mg originator tablet on two separate occasions (Tablets A-1 and A-2), two 250-mg originator tablets (Tablet B), or one 500-mg generic tablet (Tablet C). 6-Amino-4-chlorobenzene-1,3-disulfonamide )chloraminophenamide), a pharmacologically active hydrolysis product of chlorothiazide was not detected in any urine sample. Urinary recoveries of chlorothiazide after oral administration, expressed as the mean (range) percent of the dose, was only 22.0 (8.41-33.9), 15.7 (10.2-25.0), 20.7 (7.25-31.0), 18.5 (8.72-33.2), and 21.9% (6.69-41.1%) for the aqueous solution and Tablets A-1, A-2, B, and C, respectively. Considerable interindividual variation and some intraindividual variation were observed. No statistically significant difference in bioavailability existed among the aqueous solution and Tablets A-2 and B, between Tablets A-1 and C, and between Tablets A-1 and A-2.

Animals↗
PubMed1981

Dosage form design for improvement of bioavailability of levodopa IV: Possible causes of low bioavailability of oral levodopa in dogs.

Several potential mechanisms for reduced levodopa bioavailability following oral administration to dogs and humans were investigated by studying the influence of the administration route on plasma levodopa levels after intravenous, hepatoportal, and duodenal administrations to dogs. The observed average areas under the plasma concentration-time curves (AUC) of levodopa following hepatoportal injection and intravenous injection were virtually identical; but following duodenal administration a decrease in the AUC of levodopa was observed with a concomitant increase in the AUC of total dopamine. The possible involvement of intestinal microorganisms in levodopa metabolism was explored in dogs that had been administered a combination of paromomycin and kanamycin to reduce intestinal microflora. Similar patterns of plasma level profiles and urinary excretion were observed between control and treated dogs. As measured by the release of [14C]carbon dioxide from [14C]levodopa, the distribution of levodopa decarboxylase enzyme activity in various parts of the intestine was studied in homogenates prepared from isolated intestinal segments of the duodenum and upper, middle, and lower parts of the jejunum and ileum. The jejunum showed the highest decarboxylase activity followed by the ileum and duodenum. These data indicate that the reduced bioavailability of orally administered levodopa occurs as a result of metabolism by levodopa decarboxylase enzyme in the gut wall.

Administration, Oral↗
PubMed1981

Dosage form design for improvement of bioavailability of levodopa V: Absorption and metabolism of levodopa in intestinal segments of dogs.

Plasma levels of levodopa, total dopamine, and residual amounts of levodopa and its metabolites at the administered site were analyzed following administration of single 100-mg doses of levodopa in solution into isolated segments of the duodenum, jejunum, and ileum of the dog. The largest area under the plasma concentration-time curve (AUC) of levodopa during the 1.0-hr study was obtained following administration in the duodenum, followed by the jejunum and ileum. In addition, the residual amounts of levodopa and its metabolites detected at the administration sites were: ileum, 23%; jejunum, 7% and duodenum, less than 1%. The largest AUC of total dopamine was obtained following administration in the jejunum, followed by the ileum and duodenum. This order was consistent with the order of levodopa decarboxylase enzyme activity reported previously. Therefore, it can be concluded that the major absorption site of levodopa in the intestine resides in the upper small intestine. Levodopa in 10-, 50-, and 100-mg doses was administered into isolated duodenal segments. The AUC of levodopa increased nonlinearly with increasing dose. Negligible amounts of both levodopa and its metabolites were observed in the segment at 1.0 hr after administration, indicating that the duodenal absorption of levodopa was not saturable within the dose range tested.

Animals↗
PubMed1982

Serum prolactin level increase in normal subjects following administration of perphenazine oral dosage forms: possible application to bioavailability testing.

Two pilot studies were performed to determine if oral phenothiazine products could generate a significant increase in serum levels of the hormone prolactin. The two studies employed three and four healthy normal male subjects, respectively. In the first study the subjects received a screening dose, a placebo, one 8-mg perphenazine tablet, and two 8-mg perphenazine tablets. In the second study, the subjects were dosed with two 10-mg amitriptyline tablets, one 10-mg amitriptyline tablet with one combination tablet containing 10 mg of amitriptyline and 4 mg of perphenazine, and two combination tablets, each containing 10 mg of amitriptyline and 4 mg of perphenazine. In both cases the drug treatments produced a significant rise in the serum prolactin levels versus a placebo or control. This increase was defined as a prolactin response. The possible utility of this response in bioavailability testing is discussed.

Adolescent↗
PubMed1982

Relative bioavailability of commercially available ibuprofen oral dosage forms in humans.

Two human bioavailability studies were conducted to assess the in vivo performances of recently marketed 200-, 300-, and 400-mg ibuprofen capsules relative to the innovator's 300- and 400-mg tablets when administered as single oral 300- or 400-mg doses. An ibuprofen oral solution was also administered in each trial. Within each study, the products were equivalent to each other and to the oral solution with respect to the extent of ibuprofen absorption. Absorption rates, however, differed markedly among the products studied. Ibuprofen was more slowly absorbed from the 300- and 400-mg capsules than from the respective strength tablets. The 200-mg capsule exhibited an absorption rate comparable to the 400-mg tablet but more rapid than the 400-mg capsule. It was concluded that two of the duplicator's 200-mg capsules were bioequivalent to one of the innovator's 400-mg tablet. The duplicator's 300- and 400-mg capsules were bioinequivalent to the innovator's 300- and 400-mg tablets, respectively, due to their slower rates of absorption.

Adolescent↗
PubMed1982

Colorimetric determination of acetylcysteine, penicillamine, and mercaptopropionylglycine in pharmaceutical dosage forms.

A colorimetric determination of acetylcysteine, penicillamine, and mercaptopropionylglycine is described. The method is based on the oxidation of mercapto-compounds with iron(III) in the presence of 1,10-phenanthroline. The iron(II) formed was quantitatively and rapidly converted to the stable tris(1,10-phenanthroline)iron(II) complex measured spectrophotometrically at 515 nm. The results obtained from various commercial formulations indicate that the method proposed allows a simple, sensitive determination of these mercapto-drugs with good accuracy (99.5-101% recovery) and remarkable precision (RSD +/- 0.6-1.6%).

Acetylcysteine↗
PubMed1983

Convenient method of simultaneously analyzing aluminum and magnesium in pharmaceutical dosage forms using californium-252 thermal neutron activation.

A commercial antacid suspension containing aluminum hydroxide and magnesium hydroxide products was used as a model sample to study the use of a californium-252 thermal neutron activation as a method for quantifying aluminum content as well as for the simultaneous assay of aluminum and magnesium. A 3.5-micrograms californium-252 source was used for the activation, and the induced aluminum-28 and magnesium-27 activity was simultaneously measured by sodium iodide crystal gamma-ray spectrometry using dual single-channel analyzers and scalers. The antacid suspension was contained in a chamber designed with the unique capability of serving as the container for counting the induced radioactivity in addition to being the irradiation chamber itself. Ten replicate irradiations were performed, and the precision was compared with 10 replicate analyses of the antacid suspension using the official ethylenediaminetetraacetic acid titration method. For aluminum the precision was 1.4 versus 0.62% for the titration method. For the magnesium the precision was 5.3 versus 0.79% for the titration method. This pilot study demonstrated that use of more intense californium-252 sources, which are commonly available, would provide a method that is competitive with the ethylenediaminetetraacetic acid titration method in precision and in other aspects as well.

Aluminum↗