Determination of ciramadol in plasma by gas-liquid chromatography.

An analytical method for determining ciramadol concentrations in plasma was developed and evaluated for its specificity, precision, linearity, and sensitivity. GLC-electron capture detection of a dipentafluorobenzoyl derivative of the drug was used for quantitation. An isomer of the drug served as an internal standard. Resulting mean ratios of the peak height of derivatized drug to that of derivatized internal standard varied with a coefficient of variation that ranged from 3.8 to 11.1%. The mean ratio was linearly related to ciramadol content (8.75-175 ng) with a correlation coefficient greater than to 0.999. The minimum quantifiable concentration was 4 ng/ml with a 2-ml specimen. An application of this method is presented.

The metabolic disposition of norgestrel in female rhesus monkeys.

Following single intragastric doses of d- and dl-[24C]norgestrel (Ng), rhesus monkeys excreted 29.5 +/- 2.0 (SE) and 52.6 +/- 5.4% of the administered radioactivity in urine. Fecal excretion accounted for 57.1 +/- 4.0 and 37.2 +/- 4.4%, respectively. Urinary radioactivity was separated into neutral, acidic, and conjugated fractions. The neutral and conjugated fractions contained Ng; 2 alpha, 16 alpha- and 16 beta-hydroxy-Ng; 3 alpha,5 beta-tetrahydro-Ng and 16 beta-hydroxy-3 alpha,5 beta-tetrahydro-Ng and their glucuronides. However, the bulk of the radioactivity in these fractions was associated with more polar metabolites. The acidic fraction contained unstable metabolies which lose 14CO2 at pH values below 5. The most abundant of these metabolites was isolated as its stable methyl ester. The structure of a 13-ethyl-D-homogon-4-ene-3,17 alpha-dione-17 carboxylic acid is proposed for the metabolite which decomposes to 13-ethyl-D-homogon-4-ene-3,17 alpha-dione [D-homo-G]. The probable mechanism of the metabolite's formation is postulated. Quantitative differences in urinary metabolite patterns were observed following the administration of d- and dl-Ng. Ng is the major identified drug-related entity in plasma. The d-Ng concentrations in plasma measured by radioimmunoassay were in good agreement with those determined by fractionation and radiometry. The latter method indicated the presence of D-homo-G and a glucuronide of 3 alpha,5 beta-tetrahydro-Ng following the administration of d- and dl-Ng.

Excretion and stereoselective biotransformations of dl-, d- and l-norgestrel in women.

Excretion data and urinary metabolite patterns of di-, d-, and l-norgestrel were obtained from women who received a single, oral 1.5-mg dose of 14C-labeled racemic norgestrel (Ng) or one of its enantiomers. The average percentage of administered radioactivity +/- SD recovered in the urine after 7 days was 58.1 +/- 7.9% for dl-Ng, 44.8 +/- 8.9% for d-Ng, and 63.6 +/- 15.1% for l-Ng; in feces it was 23.4 +/- 7.7% (dl-Ng), 31.6 +/- 8.2% (d-Ng), and 24.8 +/- 10.7% (l-Ng). Different metabolite patterns were observed for each enantiomer in urine, and the pattern for the racemate appeared to be an approximate composite of the metabolite patterns of the two enantiomers. These differences in the metabolite pattern result from stereoselective transformations; notably 16 beta-hydroxylation of l-Ng and ring A reduction of d-Ng. Other stereoselective pathways noted were: 16 alpha- and 1 beta-hydroxylation as well as D-homoannulation of l-Ng and sulfate conjugation of l-16 beta-hydroxynorgestrel; 2 alpha-hydroxylation of d-Ng, formation of a labile neutral, polar compound which contained the norgestrel moiety in the d-form, and formation of a glucuronide of d-16 beta-hydroxynorgestre. The formation of phenolic derivatives occurred to a very minor degree from transformations of the biologically inactive l-enantiomer. With d-norgestrel, this formation occurred to an even lesser extent, if at all.

Species-related differences in the stereoselective glucuronidation of oxazepam.

The concentrations of (R)-(-)- and (S)-(+)-oxazepam glucuronides in plasma and urine of several species have been measured. The relative amounts of these diastereoisomers vary among species. Thus, in the plasma and urine of rhesus monkeys the concentrations of the R-isomer are higher, whereas in man and dog more of the S-isomer is present. In plasma and urine of miniature swine the amounts of the two diastereoisomers are about equal. In the urine of rabbits the S-isomer prevails. Similar species-related differences are observed in the in vitro formation of the isomeric oxazepam glucuronides. Homogenates of dog, miniature swine, rabbit, and rat liver produce more of the S-isomer, whereas with monkey liver the formation of (R)-oxazepam glucuronide is favored. The agreement between in vivo and in vitro data is fairly good for rhesus monkey, miniature swine, and rabbit. However, for the dog the ratio of S- to R-isomers in the liver homogenate is much higher than in plasma and urine. This species-dependent stereoselective glucuronidation of oxazepam is not related to the phylogenetic or dietary grouping of these species.

Excretion and metabolism of recainam, a new anti-arrhythmic drug, in laboratory animals and humans.

The metabolic disposition of recainam, an antiarrhythmic drug, was compared in mice, rats, dogs, rhesus monkeys, and humans. Following oral administration of [14C]recainam-HCl, radioactivity was excreted predominantly in the urine of all species except the rat. Metabolite profiles were determined in excreta by HPLC comparisons with synthetic standards. In rodents and rhesus monkeys, urinary excretion of unchanged recainam accounted for 23-36% of the iv dose and 3-7% of the oral dose. Aside from quantitative differences attributable to presystemic biotransformation, metabolite profiles were qualitatively similar following oral or iv administration to rodents and rhesus monkeys. Recainam was extensively metabolized in all species except humans. In human subjects, 84% of the urinary radioactivity corresponded to parent drug. The major metabolites in mouse and rat urine and rat feces were m- and p-hydroxyrecainam. Desisopropylrecainam and dimethylphenylaminocarboxylamino propionic acid were the predominant metabolites in dog and rhesus monkey urine. Small amounts of desisopropylrecainam and p-hydroxyrecainam were excreted in human urine. Selective enzymatic hydrolysis revealed that the hydroxylated metabolites were conjugated to varying degrees among species. Conjugated metabolites were not present in rat urine or feces, while conjugates were detected in mouse, dog, and monkey urine. Structural confirmation of the dog urinary metabolites was accomplished by mass spectral analysis. The low extent of metabolism of recainam in humans suggests that there will not be wide variations between dose and plasma concentrations.

Species differences in the pharmacokinetics of recainam, a new anti-arrhythmic drug.

The pharmacokinetics of recainam, an anti-arrhythmic drug, were compared in mice, rats, rabbits, dogs, rhesus monkeys, and man. Bioavailability was virtually complete in monkeys and dogs, 67 per cent in man and 51 per cent in rats. Non-linear kinetics between the oral and i.v. dose in rabbits precluded estimation of bioavailability. Linear plasma dose proportionality occurred in dogs between 6 and 60 mg kg-1 oral doses and rhesus monkeys between 1 and 15 mg kg-1 i.v. doses. A greater than proportional increase in the plasma AUC of recainam occurred between oral doses ranging from 54-208 mg kg-1 in mice, 25-110 mg kg-1 in rats, and 50-100 mg kg-1 in rabbits. In human subjects, the AUC/unit dose was linear between 400 and 800 mg. The terminal elimination t1/2 of recainam ranged from 1-5h in laboratory animals and man. The plasma Cmax and AUC of recainam were virtually identical after single or multiple (21 day) oral doses in dogs. After an i.v. dose, plasma clearance of recainam (l kg-1 .h) was 4.9-5.2 in rats and rabbits and 0.4-1.9 in dogs, rhesus monkeys, and man. The steady state volume of distribution was 2-5 times larger than the total body water of laboratory animals and man. Recainam was very poorly bound (10-45 per cent) to the serum proteins of rodents, rabbits, dogs, rhesus monkeys and man. In rhesus monkeys and man, recainam accounted for 10 per cent and 70 per cent, respectively, of the plasma radioactivity at 6 h post-dose. The pharmacokinetic profile of recainam in dogs most closely resembled that of man.