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At least 1,693 records · Page 94Linked to original sources
PubMed1975

Intragranular starch: comparison of starch USP and modified cornstarch.

Incorporation of starch USP or a modified cornstarch within the granules of several drug formulations was investigated. In general, the formulation containing the modified starch exhibited improved processing characteristics as well as improved tablet properties. A comparison of a granulated and a direct compression formulation of the same ingradients indicated that granulation of an active ingredient is not necessarily detrimental to its (pharmaceutical) availability.

Acetaminophen↗
PubMed1975

Intersubject variation in absorption of digoxin in normal volunteers.

The absorption of oral digoxin preparations was evaluated following single-dose administration of 0.5 mg of digoxin to 16 normal volunteers in a randomized crossover design. Absorption was estimated using the cumulative excretion of digoxin in urine for 7 days and the area under the 24-hr serum digoxin concentration curve (AUC). Significant intersubject variability was observed with both parameters, but this variability was greater for the AUC. After intravenous administration, the 7-day digoxin excretion was 68% of the dose. The elixir and a rapid dissolution tablet were significantly better absorbed (84.5 and 77.8%, respectively) than was a slow dissolution tablet (66.7%), as reflected by the fraction of the amount excreted in the urine following intravenous administration of the same dose. There was a highly significant correlation between the cumulative digoxin excretion in urine during the first 2 days compared to 7 days (r = +0.972,p less than 0.001). Bioavailability of oral digoxin preparations can be reliably determined by comparison of the cumulative 2-day excretion of digoxin following a single dose.

Administration, Oral↗
PubMed1975

Comparison of observed and predicted bioavailability of nortriptyline in humans following oral administration.

The first-pass equation based on the dose, hepatic blood flow, and total area under the plasma level-time curve after oral administration was used retrospectively to predict the bioavailability of nortriptyline after oral administration of 1 mg/kg-single oral doses to monozygotic and dizygotic twin pairs. The predicted values of bioavailability ranged from 45 to 85%, consistent with experimentally derived estimates of nortriptyline availability.

Administration, Oral↗
PubMed1975

Bioavailability of aspirin from commercial suppositories.

A comparison of the bioavailability of salicylate from five brands of commercially available aspirin rectal suppositories in an adult panel is presented. All brands show slow absorption compared to oral administration of the drug in tablet form. At best, about 40% of the dose (on the average) was absorbed when retention time in the bowel was limited to 2 hr. However, four out of the five brands give substantially lower absorption rates so that only about 20% of the aspirin is available.

Adult↗
PubMed1975

Comparative bioavailabilities from truncated blood level curves.

The period of time after administration over which blood level measurements are required to obtain a reliable bioavailability comparison of two or more formulations of the same drug was considered by the analysis of bioavailability data taken from the literature. The drugs examined, selected to represent a range of absorption and elimination half-lives, were acetaminophen, aminosalicylic acid, chloramphenicol, chlordiazepoxide, digoxin, isoniazid, phenylbutazone, sulfamethizole, tetracycline, and warfarin. For most drugs, ratios of areas under the curve changed little between the end of the absorption period and the time when blood sampling was terminated. Reliable bioavailability comparisons among different brands of the drugs apparently could have been made by blood sampling over 24 hr or less.

Acetaminophen↗
PubMed1975

Bioavailability assessment under quasi- and nonsteady-state conditions. I: theoretical considerations.

A strategy was devised to permit bioavailability estimations at quasi- and nonsteady states. The proposed method retains most attributes of a steady-state comparison without being burdened by its protractiveness. The only necessary requirements are that drug disposition obeys linear kinetics and that succeeding doses are administered during the log-linear phase free from the influence of continuing absorption.

Biological Availability↗
PubMed1975

Rapid methods for bioavailability determination utilizing urinary excretion data.

Two equations were developed which enable urinary excretion data to be utilized for estimating drug bioavailability within 12 hr-starting between one and two half-lives of the drug, depending upon the relative rates of absorption, distribution, and elimination. Both equations were examined using simulated data for both the one- and two-compartment open models. One equation was tested using literature data with excellent results.

Absorption↗
PubMed1975

Intestinal pH as a factor in selection of animal models for bioavailability testing.

Previous in situ studies showed that intestinal drug absorption is strongly influenced by intestinal pH. Three animal species considered for bioavailability testing were studied in situ to determine intestinal pH. Results from the rat and dog correlated well with results in humans, while results from the rabbit did not. The rabbit appears to be a poor candidate for attempted animal-human bioavailability correlations.

Animals↗
PubMed1976

Bioavailability assessment under quasi- and nonsteady-state conditions II: study designs.

The flexibility of bioavailability assessment at quasi-and nonsteady state is demonstrated by systematically removing experimental constraints from the study design. Mathematical expressions are derived to describe each design variation. From the resultant solutions, it is evident that the proposed method can accommodate nonuniformities in dose, dosage interval, dosage regimen, dosing cycle, sampling interval, plasma half-life, washout period, and protocol adherence. Nominal requirements for the method are linear kinetics and mean plasma concentrations estimated over time intervals beginning and ending in the log-linear region.

Biological Availability↗
PubMed1976

Influence of cholestasis on drug elimination: pharmacokinetics.

A two-compartment model representing the body and the GI tract, with elimination occurring in each compartment, was used to study, in theory, the influence of impaired biliary excretion on drug disposition. The results suggest that cholestasis can either increase or decrease a drug's half-life, depending upon the relative values of the two elimination rate constants, In all cases, however, impaired biliary excretion reduced the initial elimination of drug from the body and increased the half-life of the alpha-phase of drug disposition.

Biopharmaceutics↗
PubMed1976

Pharmacokinetics of skin penetration.

A model for estimating in vivo skin permeability coefficients is presented. Explicit expressions are derived for the permeability coefficient in terms of excretion rates and tissue absorption. The excretion rate has a linear asymptotic limit from which the permeability coefficient can be determined. The usefulness of the model is demonstrated with existing literature data.

Administration, Topical↗
PubMed1976

Bioavailability assessment under quasi- and nonsteady-state conditions III: Application.

The applicability of bioavailability assessment at quasi- and nonsteady state is illustrated with data from a study comparing two formulations of amitriptyline hydrochloride in humans. Relative bioavailability as a function of the observed mean plasma concentrations may be expressed in closed form, provided the affected intervals begin and end in the log-linear region. Alternatively, numerical, graphical and/or electronic computational techniques may be used to stimulate the appropriate [Cp(i)]sim, the proximity of which to [Cp(i)]obs is a function of relative bioavailability and omega. If a model can be found to fit the data adequately, it would be sufficient that only one sampled interval end in the log-linear phase.

Amitriptyline↗