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Biomedical subjects

L Nyberg

Publications and source records attributed to L Nyberg.

At least 109 records · Page 6Linked to original sources
PubMed1984

Pharmacokinetic parameters of terbutaline in healthy man. An overview.

After a single intravenous dose, plasma concentrations of terbutaline fall in a multi-exponential manner. The pharmacokinetic parameters are therefore preferably calculated by a non-compartmental method. Not until 6-12 h after an intravenous injection does terbutaline enter a mono-exponential decline phase. Negligence of this behaviour has produced reports of terminal half-lives in the literature, which are large underestimates. Prolonged sampling reveals that the terminal half-life of terbutaline in healthy subjects is about 17 h with an about twofold variation between subjects. This half-life determines, as a mean, about half the total area under the plasma concentration-time curve. Most studies have been performed in male subjects. On average, they have a body clearance of 3.0 mL/min/kg, 2/3 of this being the renal contribution. On a body weight basis, the renal clearance in women is at least as high as in men, possibly somewhat larger. Terbutaline's volume of distribution at steady state averages 1.6 L/kg. The systemic mean residence time of the drug is about 9 h. Terbutaline is little bound to plasma proteins but shows affinity to erythrocytes. However, clearance calculations should probably be based on the plasma concentration, because of a comparatively slow release rate from the erythrocytes. After oral administration, plasma concentration peaks of terbutaline appear within 1-4 h. Food reduces their height by about 40%. Particularly after single doses, more than one concentration peak is observed in plasma. Subjects differ considerably in their oral absorption capacity of the drug; an interindividual range of about 25-80% of the dose can be estimated. This creates a range in the extent of bioavailability of 7-26%, the decrease of the percentages being due to a high first-pass metabolism. There are strong indications that this occurs preferentially in the gut wall. The predominant metabolite of terbutaline formed in man is a sulphate conjugate. Mean bioavailability of oral terbutaline in fasting subjects is 14-15%. Food impairs the bioavailability by about one third because of reduced absorption. Despite the large variation in extent of terbutaline bioavailability between subjects, each individual behaves reproducibly from dose to dose.

Administration, Oral↗
PubMed1984

Pharmacokinetics of terbutaline therapy.

Terbutaline is widely used in respiratory medicine, in obstetrics and to some extent in cardiovascular medicine. The growing use of the drug has increased the need of pharmacokinetic information to design and optimize therapy. The clinical pharmacokinetics of terbutaline are briefly reviewed and discussed with special consideration given to therapeutic plasma concentration, bioavailability, volume of distribution, clearance and half-life of elimination.

Biological Availability↗
PubMed1984

Kinetics of terbutaline in asthmatic children.

Seven asthmatic children (8-12 years) were given terbutaline sulphate intravenously (5.5 micrograms/kg) and orally (50 micrograms/kg) one week apart. Unchanged terbutaline was measured in plasma and urine. In urine, conjugates were also assayed. The intravenous plasma concentration-time curve declined in a multiexponential manner. The terminal half-life ranged from 8.8 to 15.8 (mean 12.1) h. Body clearance (mean +/- SD) was 3.76 +/- 0.86, renal clearance 2.42 +/- 0.49 mL/min/kg. The volume of distribution at steady state was 1.57 +/- 0.19 L/kg. The extrapolated recovery of intact terbutaline in urine was 65.4 +/- 6.5% of the dose and the total recovery 80.8 +/- 8.4%. After oral administration, the recovery of intact terbutaline in urine was 6.2 +/- 1.1%. Absorption was on average 33%, but because of a mean first-pass elimination of 70%, bioavailability was 9.5 +/- 2.4%. It seems that children as a group have shorter terminal half-lives than adults and slightly higher weight-corrected clearances.

Administration, Oral↗
PubMed1984

Transfer of terbutaline into breast milk.

Terbutaline has been determined in milk and plasma from 4 nursing mothers treated with Bricanyl tablets (2.5 or 5 mg, 3 times daily) because of obstructive lung disease. Both doses produced milk concentrations of terbutaline in the range 2.5-4.6 ng/mL, which were similar to or higher than the concentrations found in plasma. The highest milk:plasma concentration ratios (up to 2.9) were observed at the beginning and end of the dosage interval. The infants in this study were estimated to have ingested about 0.4-0.6 micrograms/kg/day of terbutaline base, which corresponds to 0.2-0.7% of the daily dose per kg taken by the mothers. Terbutaline was not detectable in plasma when samples were taken from one of the infants and no symptoms of beta-adrenoceptor stimulation could be found in any of the babies.

Biological Transport↗
PubMed1975

Human pituitary luteinizing hormone. Isolation and characterization of four glycoproteins with luteinizing activity.

Two major and two minor components of human luteinizing hormone (lutropin) were isolated from whole frozen pituitaries by a procedure involving extraction of homogenized pituitaries, (NH4)2SO4 fractionation, chromatography on DEAE-cellulose, Sephadex G-100, and SE-Sephadex C-50 and electrophoresis in polyacrylamide gel. The isolation procedure was monitored by both bioassays and radioimmunoassays. Contamination of the final products by other pituitary hormone activities was very low. The four lutropin components were all homogeneous by polyacrylamide gel electrophoresis (a sieving medium) and by free zone electrophoresis (a non-sieving medium). No heterogeneity was observed when the components were studied in the ultracentrifuge by sedimentation-equilibrium technique. The molecular weights of the components were in the range of 34 000-40 000. Sedimentation velocity experiments with the two major components revealed in each case one boundary with S20,W values of 3.2 S and 3.5 S. Further evidence for the homogeneity of the components was the observation of only one precipitin line for each component upon immunodiffusion against a rabbit anti-human lutropin serum. Amino acid and carbohydrate analyses indicated close similarity among the four components. From the analysis data the molecular weights of the components were calculated to be 31 000-33 000.

Amino Acids↗
PubMed1975

Absorption of digoxin in man after oral and intrasigmoid administration studied by portal vein catheterization.

The absorption of digoxin has been studied in fasting patients undergoing transumbilical, portal catheterization for diagnostic purposes. A purely aqueous solution was administered orally in 4 patients and in the sigmoid colon in 2 patients. Blood samples were taken simultaneously from the portal and a peripheral vein. Plasma digoxin concentrations were determined by radioimmunoassay. Digoxin appeared early in the blood after oral administration; the average peak of porto-peripheral concentration differences was at 18 min. After intrasigmoid administration, absorption was slower, and no distinct peaks were found. Calculation of the mean amounts absorbed showed that half the dose had been absorbed via the portal vein during 2 hours in the oral study and during6 hours in the intrasigmoid test. Approximately 2/3 of the dose had been absorbed during 6 hours after oral dosing. The absorption rate was estimated taking into account the decreasing amount of drug left to be absorbed at different times. After cral administration, the mean peak rate was found to correspond to an absorption half-time of 0.78 h, which was more than 20 times faster than the rate after 6 h. The mean rate after intrasigmoid administration appeared to be about 1/3 of that after oral dosing. Physiological factors that might account for these differences in absorption rate are discussed.

Administration, Oral↗