Search results for "Availability"
showing 10 items of 510 documents
Bioavailability of pharmaceuticals in waters close to wastewater treatment plants: Use of fish bile for exposure assessment
2012
Pharmaceuticals are ubiquitous in surface waters as a consequence of discharges from municipal wastewater treatment plants. However, few studies have assessed the bioavailability of pharmaceuticals to fish in natural waters. In the present study, passive samplers and rainbow trout were experimentally deployed next to three municipal wastewater treatment plants in Finland to evaluate the degree of animal exposure. Pharmaceuticals from several therapeutic classes (in total 15) were analyzed by liquid chromatography-tandem mass spectrometry in extracts of passive samplers and in bile and blood plasma of rainbow trout held at polluted sites for 10 d. Each approach indicated the highest exposure…
Modelling intestinal absorption of salbutamol sulphate in rats
2005
The objective was to develop a semiphysiological population pharmacokinetic model that describes the complex salbutamol sulphate absorption in rat small intestine. In situ techniques were used to characterize the salbutamol sulphate absorption at different concentrations (range: 0.15-18 mM). Salbutamol sulphate at concentration of 0.29 mM was administered in presence of verapamil (10 and 20 mM), grapefruit juice and sodium azide (NaN3) (0.3, 3 and 6 mM). Different pharmacokinetic models were fitted to the dataset using NONMEM. Parametric and non-parametric bootstrap analyses were employed as internal model evaluation techniques. The validated model suggested instantaneous equilibrium betwee…
Low bioavailability of amoxicillin in rats as a consequence of presystemic degradation in the intestine.
1994
Several studies have been carried out to elucidate the causes of the low oral bioavailability of amoxicillin in rats. The hepatic first-pass effect of the antibiotic was estimated by comparing the area under the plasma drug concentration-versus-time curve from time zero to infinity (AUC0-infinity) obtained after injecting the drug into a mesenteric vein with the AUC0-infinity value obtained after injecting the drug into the jugular vein of conscious rats. No hepatic first-pass effect was detected. The bioavailability of amoxicillin after intraduodenal administration was only 51%, and the fraction of the dose remaining in the intestine at the end of the experiment was 4.5%. This was far less…
Free choline and choline metabolites in rat brain and body fluids: sensitive determination and implications for choline supply to the brain.
1993
In the central nervous system, choline is an essential precursor of choline-containing phospholipids in neurons and glial cells and of acetylcholine in cholinergic neurons. In order to study choline transport and metabolism in the brain, we developed a comprehensive methodical procedure for the analysis of choline and its major metabolites which involves a separation step, selective hydrolysis and subsequent determination of free choline by HPLC and electrochemical detection. In the present paper, we report the levels of choline, acetylcholine, phosphocholine, glycerophosphocholine and choline-containing phospholipids in brain tissue, cerebrospinal fluid and blood plasma of the untreated ra…
Pharmacokinetics and bioavailability of diclofenac in the rat.
1991
Diclofenac sodium is a widely used drug with interesting absorption and disposition features when administered to laboratory animals. The present study was undertaken to assess the pharmacokinetics of the drug after iv and gastrointestinal dosing to rats. Renal excretion of unchanged drug was negligible, but biliary excretion of the drug (unchanged and conjugated) was detected in bile duct-cannulated rats; it accounted for 27.2 and 31.2% of the total dose following iv and intraduodenal administration, respectively. Most of the drug excreted in the bile was conjugated diclofenac; unchanged drug accounted for only 4.7 and 5.4% of total diclofenac excreted in the bile after iv and intraduodena…
The influence of active secretion processes on intestinal absorption of salbutamol in the rat.
2001
Abstract Salbutamol was perfused in the small intestine of rat using a standard rat gut ‘in situ’ preparation: (1) in inhibitor-free solution at seven different concentrations (0.15, 0.29, 1.20, 5.0, 9.0, 13.0 and 18.0 mM); (2) at a 0.29 mM concentration – thought to be close to the allometric dose in man – in the presence of a non-specific enzyme inhibitor, sodium azide (0.3, 3.0 and 6.0 mM); and (3) at 0.29 mM in the presence of a selective secretion inhibitor, verapamil (10.0 and 20.0 mM). In free solution, the mixed-order rate constants, k ′ a , of salbutamol increase as the solute concentration increases until an apparent asymptotic value is reached. This could be due to the saturation…
Hepatic extraction of isosorbide dinitrate in cardiac patients
1983
Hepatic extraction of organic nitrates, including that of isosorbide dinitrate (ISDN), has been thought to be nearly complete in man but has never been directly measured. We examined the time course of plasma ISDN and metabolite concentrations in arterial and hepatic venous blood in four cardiac patients receiving an intravenous ISDN infusion. Apparent hepatic extraction of ISDN was high (90%) at the beginning of infusion but fell to about 44% 1 hr after termination of infusion. The decrease in ISDN concentration gradient across the liver correlates with an increase in plasma isosorbide-5-mononitrate concentration, but a cause-and-effect relationship resulting from metabolite inhibition can…
Bioavailability of nevirapine in rats after oral and subcutaneous administration, in vivo absorption from gastrointestinal segments and effect of bil…
2011
Abstract Nevirapine is a non-nucleoside reverse transcriptase inhibitor of human immunodeficiency virus type-1. The usual dosing regimen is 200 mg twice/day. Reducing the dosing frequency would significantly improve treatment adherence and quality of life of patients. To study new forms of administration, it is necessary to do pre-clinical studies and know the absorption characteristics of nevirapine in laboratory animals. However, there are no studies about its bioavailability in rats and hardly any about its pharmacokinetic. The objectives of this study were to describe the pharmacokinetics of nevirapine in rats after intravenous, oral and subcutaneous administration, to assess its absorp…
Ethical consumerism: a view from Finland
2004
Business ethics and corporate social responsibility have gained more attention in recent years. However, the consumers’ perspective on ethics is still a little researched area. This study reports a survey ( n = 713) on the views of Finnish consumers about ethics in trade. Consumers’ willingness to promote business ethics as well as the obstacles to ethical consumption are investigated. The results of the study show that while the majority of the respondents regard business ethics as important, this attitude does not translate into their choice behaviour. Consumers are uncertain about which products and firms follow ethical rules and which do not. The most important obstacles to ethical cons…
Nanostructured Lipid Carriers-Containing Anticancer Compounds: Preparation, Characterization, and Cytotoxicity Studies
2007
This article describes the development of nanostructured lipid carriers (NLC) as colloidal carriers for two antitumor compounds that possess a remarkable antineoplastic activity. But their limited stability and low solubility in water could give a very low parenteral bioavailability. Results revealed an enhancement of the cytotoxicity effect of drug-loaded NLC on human prostate cancer (PC-3) and human hepatocellular carcinoma (HuH-6, HuH-7) cell lines with respect to that of both free drugs. Results of characterization studies strongly support the potential application of these drugs-loaded NLC as prolonged delivery systems for lipophilic drugs by several administration routes, in particula…