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Biomedical subjects

W F Trager

Publications and source records attributed to W F Trager.

At least 109 records · Page 6Linked to original sources
PubMed1976

Warfarin: stereochemical aspects of its metabolism in vivo in the rat.

The biotransformation of the R and S isomers of warfarin was investigated in the rat. The formation of 7-hydroxywarfarin was stereoselective for the R enantiomer, while the formation of 4'-hydroxywarfarin was stereoselective for the S enantiomer. The 6-, 8-, and benzylic hydroxylation of both isomers was approximately the same. The reduction of the side chain ketone function of warfarin to the corresponding diastereomeric warfarin alcohols was stereoselective for the S isomer. The reduction also displayed a degree of stereospecificity with S reduction occurring predominantly. The results of the in vivo study agree in many cases with a previous in vitro investigation. However, differences between the in vitro and in vivo studies do exist and suggest that secondary stereoselective biotransformation routes occur in vivo and that the microsomal and soluble enzymes employed in the in vitro study may have been disrupted during isolation. Large amounts of polar labile conjugates of R and S warfarin, and metabolites were found in the urine. The 4-hydroxyl group of the coumarin ring appears to be the position of conjugation and this process appears to be regio and stereoselective.

Animals↗
PubMed1975

The rapid identification of a new metabolite of warfarin via a chemical ionization mass spectrometry ion doublet technique.

An ion doublet chemical ionization mass spectrometry technique was utilized for the rapid detection and elucidation of the structure of a new hydroxylated metabolite of the oral anticoagulant warfarin. This technique involves the use of a 50:50 mixture of stable isotope labeled and unlabeled drug. With this procedure ions found in the mass spectrum which are associated with the administered drug can be identified unambiguously. The unknown metabolite from rat liver microsomal preparations was identified as benzylic hydroxywarfarin by reincubating the microsomes with warfarin specifically labeled in the benzylic position and observing the subsequent loss of label in the product. The ion doublet technique was also employed in a single human study, and benzylic hydroxywarfarin was detected and identified.

Animals↗
PubMed1975

Primary and beta-secondary deuterium isotope effects in N-deethylation reactions.

Lidocaine (1), labeled specifically with deuterium in the alpha-methylene (lidocaine-d4,2) and beta-methyl (lidocaine-d6,3) carbon atoms of the terminal amino group, was used to probe the mechanism of oxidative N-deethylation by rat liver microsomes. The reaction rates were determined by measuring the formation of acetaldehyde colorimetrically. This general assay for oxidative N-deethylation reactions has the advantages of being rapid, producing a relatively stable colored derivative and being linear over the range of 0.25-4 mug of acetaldehyde formed per milliliter of incubate. Deuterium substitution at the methylene carbon atoms, the presumed site of initial oxygen insertion, revealed a kH/kD = 1.49 +/- 0.11 and a KmD/KmH = 1.23. Deuterium substitution on the terminal methyl groups showed a kH/kD = 1.52 +/- 0.10 and a KmD/KmH = 0.92. The results are explained in terms of both primary and secondary isotope effects on a possible rate-determining step in the N-deethylation sequence.

Acetaldehyde↗
PubMed1975

Biotransformation of phenprocoumon in the rat.

The metabolic fate of phenprocoumon [3-(alpha-ethylbenzyl)-4-hydroxycoumarin] in the rat is described. The major metabolites, 4',-6-,7-, and 8-hyproxyphenprocoumon, have been identified yb mass spectrometry, TLC, and uv and compared with authentic smaples. Metabolites are mainly excreted via the feces. The results are compared with those previously reported for warfarin.

Animals↗
PubMed1974

Warfarin. Stereochemical aspects of its metabolism and the interaction with phenylbutazone.

An examination of the metabolic fate of the R and the S isomers of warfarin revealed that the two isomers were metabolized by different routes. R warfarin was oxidized to 6-hydroxywarfarin and was reduced to the (R,S) warfarin alcohol. In contrast, S warfarin was oxidized to 7-hydroxywarfarin and was reduced to the (S,S) warfarin alcohol. S warfarin was also oxidized to 6-hydroxywarfarin. These observations suggested that interactions between warfarin and other drugs might be manifest stereo-specifically, i.e., have a different effect on the isomers of warfarin, so a series of experiments were conducted with each isomer of warfarin, before and after phenylbutazone. The plasma clearance of S warfarin was slowed from 3.1 to 1.1% per h in one subject and from 2.3 to 1.6% per h in another. In contrast, the clearance of R warfarin was increased from 1.5 to 3.0% per h and from 0.9 to 1.6% per h in two subjects after phenylbutazone. The rate of clearance of racemic warfarin was unaffected by phenylbutazone; the depression of the rate of clearance of the S isomer masked the stimulation of the clearance of the R isomer. Since S warfarin is five times more potent an anticoagulant than R warfarin, it is concluded that inhibition of the metabolism of S warfarin provides one mechanism for the augmented anticoagulation which follows phenylbutazone.

Blood Coagulation↗
PubMed1970

Warfarin metabolism in man: identification of metabolites in urine.

After administration of the coumarin anticoagulant racemic warfarin to normal humans, seven fluorescent compounds were chromatographically separated from extracts of their urine. Four of these were identified using mass spectrometry, thin-layer chromatography, and ultraviolet absorption spectroscopy. One metabolic pathway, reduction of the acetonyl side chain of warfarin, resulted in the formation of a second asymmetric carbon atom, and two diastereoisomer alcohols were identified. These warfarin alcohols are structurally similar to pharmacologically active coumarin derivatives. They have not been reported in animal studies. In addition, 6- and 7-hydroxywarfarin were identified. These are the first studies to document the metabolic fate of warfarin in the normal human.

Alcohols↗