Liquid chromatographic assay for debrisoquine and 4-hydroxydebrisoquine in urine

Separation and quantitation of debrisoquine and 4-hydroxydebrisoquine in human urine by capillary electrophoresis and high-performance liquid chromatography

A comparative study on the use of reversed-phase high-performance liquid chromatography (RP-HPLC) and capillary electrophoresis (CE) for the determination of debrisoquine (D) and its metabolite, 4-hydroxydebrisoquine (4-HD), in human urine is presented. Four different urine pre-treatments are compared for purification of samples prior to their injection in HPLC and CE. The use of a solid-phase extraction with a C18 cartridge provides the best results for the urine sample treatment, with good recoveries, i.e., 94.5% for D and 93.4% for 4-HD, and high reproducibility, i.e., R.S.D. N = 10 values of 1.7% and 1.2%, respectively. Under our separation conditions it is shown that CE is twice as fast and provides slightly better analysis time reproducibility than HPLC for this type of sample. Both the sensitivity and peak area reproducibility are better when HPLC is used. The two techniques show good agreement when employed for determination of phenotypes for hydroxylation, which seems to corroborate the usefulness of CE for this type of study.

Improved high-performance liquid chromatographic determination of debrisoquine and 4-hydroxydebrisoquine in human urine following direct injection

A sensitive and specific reversed-phase high-performance liquid chromatographic assay was developed for the determination of debrisoquine and 4-hydroxydebrisoquine in urine. The urine samples were directly injected following an ether clean-up step which eliminated interference. Separation of the analytes was achieved using a mobile phase consisting of acetonitrile-methanol-0.02 M heptane sulfonic acid (pH 3.0) (6:37:57) and a mu Bondapak C18 analytical column. The assay utilizes fluorescence detection at 208 nm (ex) and 562 (em). The within-day and between-day coefficients of variation were < or = 10% for both components and accuracy was within 12%. The method is suitable of pharmacogenetic studies utilizing debrisoquine.

Determination of debrisoquine and 4-hydroxydebrisoquine in urine by high-performance liquid chromatography with fluorescence detection after solid-phase extraction

A simple, selective and sensitive method has been developed to determine debrisoquine and 4-hydroxydebrisoquine in human urine. Separation of the analytes was obtained using a mobile phase of 0.1 M sodium dihydrogen phosphate-acetonitrile (87:13, v/v) and a muBondapak C18 column. The column effluent was monitored with fluorescence detection at 210 nm (ex) and 290 nm (em). Rapid sample preparation was achieved by solid-phase extraction columns (Bond Elut CBA, 3 ml capacity) which provided excellent recovery values for both compounds. The cost per sample using this approach could be minimized by column regeneration and re-use. The within-day and the day-to-day reproducibilities were less than 7% for both components. The method was shown to be suitable for the study of the debrisoquine-sparteine type genetic polymorphism in man.

Debrisoquine metabolism in Chinese patients with Alzheimer's and Parkinson's diseases

We determined the oxidative phenotype and metabolic ratio of debrisoquine in 96 Chinese patients with Alzheimer's disease (n = 12), Parkinson's disease (n = 55), and using patients with stroke and cervical spondylosis as controls (n = 29). We did not find any difference in debrisoquine metabolic phenotype among Parkinson's disease, Alzheimer's disease, and control patients as judged by chi-square analysis. In addition, the metabolic ratio of all our patients was less than 12.6. The result suggested that Chinese patients with Parkinson's disease and Alzheimer's disease metabolize debrisoquine at a velocity not different from that of their Western counterparts even though the frequency distribution of debrisoquine metabolism phenotyping in these two populations is quite different.

Disposition of minaprine in animals and in human extensive and limited debrisoquine hydroxylators

1. The disposition of 14C-minaprine was studied after oral administration of 5 and 20 mg/kg to rats, dogs and macaques, and of 200 mg to human volunteers with a genetic status of either limited or extensive hydroxylation of debrisoquine. 2. The drug was readily absorbed and a large proportion of the administered radioactivity was excreted within 48 h. The total excretion over 5 days ranged from 83% in monkeys to almost 100% in human with a status of extensive hydroxylators. 3. In the two limited hydroxylators Cmax values of total radioactivity in plasma were 4.6 and 3.7 mg equiv/l respectively. Those in the two extensive hydroxylators were 1.9 and 1.6 respectively. The highest value in the animal species was 8.1 in rats at a dose of 20 mg/kg. Plasma Cmax values of minaprine were 4.0 and 1.4 mg/l in limited hydroxylators and 0.35 and 0.23 mg/l in extensive ones. The highest value in the animal species was 2.7 mg/l in dogs treated with 20 mg/kg. 4. In rats and dogs, the ratios of the plasma AUC values for 20 mg/5 mg doses were close to those of the ratios of the doses administered, whereas in the macaque a slower clearance of radioactivity occurred with the higher dose (t 1/2 beta 5.5 h at 5 mg/kg dose versus 25.7 h at 20 mg/kg dose). 5. Marked species differences were observed in the metabolic pathways. The dog and limited hydroxylators showed higher levels of minaprine and its N-oxide (M4) whereas p-hydroxy-minaprine (M3) prevailed in monkey, rat and extensive hydroxylators. 6. In dogs only, seizures appeared within 10-15 min after dosage with minaprine at 20 mg/kg, when the concentrations of minaprine in erythrocytes (6.9 mg/l) and of M4 in plasma (0.40 mg/l) and erythrocytes (0.25 mg/l), were high. 7. The measurements and clinical observations indicate that onset of an adverse behavioural response in humans is unlikely at the dose of 200 mg.

Determination of debrisoquine and metabolites in human urine by gas chromatography-mass spectrometry

A gas chromatographic-mass spectrometric analysis has been developed for the determination of debrisoquine and its metabolites in the urine of healthy individuals (controls) and patients with chronic renal failure. The sensitive and specific assay comprises selected-ion monitoring of the drug and the metabolites 4-hydroxydebrisoquine and 8-hydroxydebrisoquine using guanoxan as the internal standard. The limit of detection is ca. 0.2 microgram/ml. The clinical study shows that the healthy individuals and patients with chronic renal failure can be divided in two groups of extensive metabolizers and poor metabolizers, respectively. The extensive metabolizers excreted large amounts of 4-hydroxydebrisoquine and minor amounts of 8-hydroxydebrisoquine. The poor metabolizers excreted small amounts of 4-hydroxy metabolite, and no 8-hydroxydebrisoquine was detected in the urine.

Dextromethorphan: polymorphic serum pattern of the O-demethylated and didemethylated metabolites in man

1. The interindividual differences in serum concentrations of dextromethorphan (DM) and its metabolites were studied in 29 healthy subjects given 120 mg orally. They were also phenotyped according to the urinary ratio of debrisoquine and 4-hydroxy-debrisoquine. 2. Four (14%) subjects were found to be poor metabolizers (PM) with a dextromethorphan/dextrorphan metabolite ratio in plasma of 3.6 or more compared with extensive metabolizers (EM) with a ratio of 0.11 or less. Significant levels of 3-hydroxymorphinan were measurable in all individuals except two, both of whom were PMs. This subdivision corresponded to the phenotype determined by the metabolic ratio of debrisoquine (r = 0.92). 3. Twelve of the 29 subjects reported adverse drug reactions after dextromethorphan administration compared with none after placebo.

Xenobiotic metabolism in motor neuron disease

Debrisoquine, carbocysteine, and paracetamol were selected as safe drugs to investigate the ability of the liver's microsomal system to oxidise carbon, oxidise sulphur, and conjugate sulphate in patients with motor neuron disease (MND), other hospital patients, and healthy volunteers. Subjects with poor sulphur-oxidising and sulphur-conjugating activities were heavily over-represented in the MND group.

Stereoselectivity of the 4-hydroxylation of debrisoquine in man, detected by gas chromatography/mass spectrometry

A stable isotope assay for the quantification of debrisoquine (1) and its major urinary metabolite 4-hydroxydebrisoquine (2) is described. The method consists of extractive derivatization of 1 and 2 by use of 1,3-diketones, chiral derivatization of the 4-hydroxy group of 2, and gas chromatography/negative ion chemical ionization mass spectrometry in the presence of deuterated analogues of 1 and 2. In comparison with synthetic R-(-)-2 and S-(+)-2 it is shown that in vivo benzylic 4-hydroxylation of 1 is highly stereoselective, leading predominantly to S-(+)-4-hydroxydebrisoquine (enantiomeric excess greater than or equal to 90%).