Biomedical subjects

T Blaschke

Publications and source records attributed to T Blaschke.

21 records · Page 2Linked to original sources

PubMed1978

Probenecid inhibition of methotrexate-cerebrospinal fluid pharmacokinetics in dogs.

Cerebrospinal fluid (CSF) and plasma concentrations of methotrexate (MTX) were followed in dogs for 72 hours after intracisternal injection of MTX with and without probenecid pretreatment. CSF levels declined as a biexponential function of time. Probenecid pretreatment of the animals prolonged the second phase half-disappearance time of MTX from 5.20 +/- 0.89 to 7.086 +/- 0.23 hours (mean +/- SD). The peak mean plasma concentration of MTX was lower in the presence of probenecid. Also, the rate of decline of plasma MTX concentrations was slower after treatment with probenecid, with mean half-disappearance times of 7.60 +/- 0.77 and 11.32 +/- 1.08 hours. These CSF and plasma data support the proposal that probenecid inhibits the transfer of MTX from CSF to blood.

Animals↗

PubMedDate not supplied

Improving drug dosing in hospitalized patients: automated modeling of pharmacokinetics for individualization of drug dosage regimens.

Many clinical useful drugs have a narrow range of blood concentrations which are both safe and efficacious. Inter-individual and intra-individual variations in drug disposition are important factors causing blood concentrations of drug to fall outside of the therapeutic range. Modeling of the pharmacokinetics of the individual offers an effective approach to the problem of variation in drug disposition. Previous approaches for the modeling of individual pharmacokinetics have required either extensive computations or access to computer software and hardware in the clinical environment, and special expertise to interpret the results. This paper describes a prototype computer program, PK Monitor, which can, when connected with an appropriate interface, automatically monitor drug dosing and recommend changes that may be required to obtain blood concentrations in the therapeutic range. The software can also detect the occurrence of change in drug disposition which will lead to concentrations outside of the therapeutic range, identify potentially erroneous blood concentration measurements, and assess the need for further blood concentration measurements. This program will be an integral part of the MENTOR therapeutic monitoring system of programs. PK Monitor awaits a complete evaluation with the rest of the MENTOR system, but preliminary simulations suggest reasonable sensitivity and specificity in monitoring for unexpected data and change.

Drug Administration Schedule↗

PubMedDate not supplied

Prazosin first-pass metabolism and hepatic extraction in the dog.

The short half-life, low plasma concentrations, and extensive biotransformation of prazosin suggest that it might be subject to extensive first-pass metabolism. Bioavailability, disposition, and hepatic extraction were studied in the dog. In conscious dogs whole blood prazosin concentrations were measured after oral and intravenous administration of the drug. Anesthetized dogs were used to measure prazosin concentrations in arterial and hepatic venous blood samples drawn simultaneously. The bioavailability of prazosin was 0.38 +/- 0.11. In anesthetized dogs the hepatic extraction of prazosin was 0.47 +/- 0.08 for a predicted availability of 0.53 +/- 0.08. Pharmacokinetic parameters were similar in conscious and anesthetized animals. Following intravenous administration to conscious dogs, prazosin concentrations in whole blood declined with a fast half-life of 3.9 +/- 1.74 min and a slow half-life of 153 +/- 24 min, the volume of distribution at steady state being 48.6 +/- 15.3 liters in dogs (mean weight, 22.6 kg). We conclude that prazosin availability following oral administration is low and that first-pass hepatic metabolism is largely responsible for this. A one-compartment model adequately describes prazosin pharmacokinetics in the dog.

Animals↗