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PubMed1981

Evaluation of methods for estimating population pharmacokinetic parameters. II. Biexponential model and experimental pharmacokinetic data.

Individual pharmacokinetic parameters quantify the pharmacokinetics of an individual, while population pharmacokinetic parameters quantify population mean-kinetics, interindividual variability, and residual variability, including intraindividual variability and measurement error. Individual pharmacokinetics are estimated by fitting individual data to a pharmacokinetic model. Population pharmacokinetic parameters have been estimated either by fitting all individuals' data together as though there were no individual kinetic difference, the naive pooled data (NPD) approach, or by fitting each individuals' data separately and then combining the individual parameter estimates, the two stage (TS) approach. A third approach, NONMEM, takes a middle course between these. This study provides further evidence of NONMEM's validity by comparing, using simulation, the three approaches on three types of data sets corresponding to three typical types of pharmacokinetic studies. The estimates of population parameters provided by the NPD method are poorer than those provided by either of the other methods. The estimates provided by the TS method are adequate for mean values and for residual variability, but not for interindividual kinetic variability. NONMEM's estimates are as good as those of the TS method for mean parameters and for residual variability, and considerably better for interindividual variability. The latter estimates are still not acceptable in an absolute sense. This is probably due, not to an intrinsic fault of the method (as it is in the case of the TS approach), but to an insufficient number of individuals being studied.

Biopharmaceutics↗
PubMed1981

Clinical bioavailability evaluation of a controlled release formulation of diazepam.

A controlled release formulation of diazepam was compared to equal daily dose of the trade tablet under single day and steady-state conditions. Virtually no differences were found in the mean steady-state concentrations of diazepam or its metabolites, N-desmethyldiazepam, when the subjects received the 5 mg trade table three times daily or the 15 mg controlled release formulation once daily. Similarly, there was no difference in mean diazepam or N-desmethyldiazepam plasma concentrations when single doses of the controlled release formulation were give to fed or fasted volunteers. These data indicate that the controlled release formulation produces plasma concentrations of diazepam and N-desmethyldiazepam comparable to those achieved with the same daily dose of the trade product given three times daily, suggesting that these regimens can be used interchangeably.

Adult↗
PubMed1990

[Industrial production of monoclonal antibodies].

Murine monoclonal antibodies (mabs) are produced in either mouse ascites or bioreactors (spinner culture, stirred-tank reactor, airlift reactor, hollow-fiber reactor). Human mabs are produced solely in bioreactors. Encapsulation represents a special technology. Hybridoma cells have to be adapted prior to growth in bioreactors. Of crucial importance is the construction of over-producing cell lines by cell- and gene-technological methods. Manipulated cell lines often produce modified mabs.

Animals↗
PubMed1975

[Cardiac effects and glycoside concentrations in serum and urine after oral administration of beta-methy-digoxin to healthy individuals (author's transl)].

Six healthy individuals were digitalized orally with beta-methyl-digoxin. The serum glycoside concentration, determined radioimmunologically at the end of the digitalization period was 1.2 +/- 0.22 ng/ml. At this period of time renal excretion attained 55.9% of the daily administered oral dose. The calculated renal clearance of beta-methyl-digoxin was 63 +/- 8.1 ml/min e. g. 57.5 +/- 8.3 ml/min/1.73 m2. After discontinuation of the glycoside the serum half life was 54 h. During the digitalization period the cardiac glycoside effects could be measured by ECG changes, especially a shortening of the QT interval as well as a shortening of the left ventricular ejection time and the pre ejection period, corrected for the heart rate.

Administration, Oral↗
PubMed1975

[Comparison of digitoxin bioavailability from tablets and elixir during maintenance therapy (author's transl)].

The bioavalability of digoxin tablets and solution has been studied during maintenance therapy in a cross over study. Each preparation was given over a period of at least 7 days to patients with compensated congestive heart failure. Urine concentrations and plasma levels were analysed for digitoxin. There was no significant difference between the two preparations. Determination of steady state serum concentrations and urinary excretion during maintenance therapy as an index of bioavalability are more cumbersome than a single dose study. From a pharmacokinetic point of view however, analyses of steady-state conditions are preferable to a single dose study. In addition, steady state of drug input and output resembles the usual digitalis therapy.

Administration, Oral↗