In vitro and in vivo metabolism of the progestagen Org 30659 in several species.

The metabolism of Org 30659 [(17alpha)-17-hydroxy-11-methylene-19-norpregna-4, 15-dien-20-yn-3-one], a new potent progestagen currently under clinical development by NV Organon for use in oral contraceptive and hormone replacement therapy, was studied in vivo after oral administration to rats and monkeys and in vitro using rat, rabbit, monkey, and human liver microsomes and rat and human hepatocytes. After oral administration of [7-3H]Org 30659 to rats and monkeys, Org 30659 was extensively metabolized in both species. Fecal excretion appeared to be the main route of elimination. In rats, opening of the A-ring, resulting in a 2-OH,4-carboxylic acid, 5alpha-H metabolite of Org 30659, was the major metabolic route in vivo. Other metabolic routes involved the introduction of an OH group at C15beta, followed by a shift of the Delta15-double bond to a 16/17-double bond with subsequent removal of the OH group at C17 and reduction of the 3-keto,Delta4 moiety followed by sulfate conjugation of the 3-OH substituent. These metabolic routes observed in vivo were also major routes in incubations with rat hepatocytes. In rat liver microsomes, Org 30659 was metabolized by reduction of the 3-keto,Delta4 moiety. Rat hepatocyte incubations with Org 30659 were more representative of the in vivo metabolism of Org 30659, compared with rat microsomal incubations. Both in vitro and in vivo, the majority of the metabolites were 3alpha-OH,4,5alpha-dihydro derivatives. In monkeys, Org 30659 was mainly metabolized at the C3- and C17-positions in vivo. The 3-keto moiety was reduced to both 3beta-OH and 3alpha-OH substituents. In addition to phase I metabolites, glucuronic acid conjugates were observed in vivo. In monkey liver microsomes, the 6beta-OH metabolite of Org 30659 was the major metabolite present. Similar to the monkey liver microsomes, rabbit and human liver microsomes converted Org 30659 to the 6beta-OH metabolite. This metabolite was also the major metabolite in incubations with human hepatocytes.

In vitro and in vivo metabolism of desogestrel in several species.

The metabolism of desogestrel (13-ethyl-11-methylene-18, 19-dinor-17alpha-pregn-4-en-20-yn-17-ol), an orally active progestogen, was studied in vivo after administration of single oral doses to rats and dogs and in vitro using rat, rabbit, dog, and human liver microsomes. Metabolites were isolated and identified by NMR and MS analysis. After oral administration of [3H]desogestrel to rats and dogs, desogestrel was extensively metabolized in both species. Radioactivity was predominantly eliminated in the feces. In rats, desogestrel was metabolized mainly at the C3-, C5-, C11-, and C15-positions. Both in vivo and in vitro, the majority of metabolites were 3alpha-hydroxy,4,5alpha-dihydro derivatives. Other main metabolic routes for desogestrel in rats were 15alpha-hydroxylation and epoxidation of the C11-methylene moiety. In addition to phase I metabolites, glucuronic acid and sulfate conjugates of desogestrel were observed in vivo. In dogs, desogestrel was mainly metabolized at the C3- and C17-positions. In contrast to the rat metabolites, metabolites isolated from dog urine or feces were mainly 3beta-hydroxy,4,5alpha-dihydro derivatives. In most of the metabolites present in dog urine and feces, the five-membered D-ring was expanded to a six-membered D-ring, i.e. D-homoannulation to a 17A-keto-D-homo ring. D-Homo metabolites, which were major metabolites in plasma, urine, and feces of dogs, were not observed in vitro. In dog liver microsomes, the 3-keto metabolite of desogestrel was the major metabolite. Similarly to dog liver microsomes, rabbit and human liver microsomes mainly converted desogestrel to its 3-keto metabolite. Predominant positions for further hydroxylation of the 3-keto metabolite of desogestrel were the C6-position (6beta-hydroxy) and the ethyl substituent at the C13-position, for both species.

Pharmacokinetics and biotransformation of mirtazapine in human volunteers.

This paper investigated the pharmacokinetics and biotransformation of mirtazapine in healthy human volunteers. The results showed that the area under the plasma drug concentration-time curve (AUC) of mirtazapine in human plasma appeared to be three times higher than the AUC of demethylmirtazapine. As mirtazapine is marketed as a racemic mixture and both enantiomers possess pharmacological properties essential for the overall activity of the racemate, the pharmacokinetics of mirtazapine were examined and appeared to be enantioselective. The R(-)-enantiomer showed the longest elimination half-life from plasma. This was ascribed to the preferred formation of a quaternary ammonium glucuronide of the R(-)-enantiomer. This glucuronide may be deconjugated, leading to a further circulation of the parent compound, thus causing a prolongation in the elimination half-life. The S(+)-enantiomer was preferentially metabolised into an 8-hydroxy glucuronide. Other metabolic transformation pathways found for mirtazapine were demethylation and N-oxidation. Mirtazapine was extensively metabolised and almost completely excreted in the urine (over 80%) and faeces within a few days after oral administration.

Biotransformation of trans-5-chloro-2-methyl-2,3,3a,12b-tetrahydro-1-H-dibenz[2,3:6,7]oxepin o [4,5-c]pyrrolidine maleate in rats.

The metabolism of trans-5-chloro-2-methyl-2,3,3a,12b-tetrahydro-1 H-dibenz[2,3:6,7]oxepinol [4,5-c]pyrrolidine maleate (Org 5222) labelled with [3H] or [14C] was investigated in Wistar rats. Metabolites were identified by mass spectrometry, 13C- and 1H-NMR analysis, IR spectroscopy and, wherever possible, by comparison with authentic reference compounds. The metabolites found in plasma, bile, faeces and urine revealed the processes of metabolism in which Org 5222 underwent oxidation to yield an N-oxide existing in two diastereoisomeric forms, or N-demethylation to yield a demethyl metabolite. A novel metabolite was found in bile, viz. a carbamate glucuronide, formed from an intermediate carbamic acid, derived from the addition of CO2 to the demethyl metabolite.

The discrimination between human, porcine and bovine insulin with 1H NMR spectroscopy.

The 1H- and 1H-1H correlation (COSY) NMR spectra of human, porcine and bovine insulin have been recorded. The 1.1-1.5 ppm regions of these spectra show the methyl signals of the alanine and threonine residues. The number of alanines and threonines differs for the three insulins and thus allows an easy discrimination with NMR.