Simple method of methylation for gas chromatographic analysis of S-benzyl-N-acetylcysteine,a metabolite of toluene,in human urine

A simplified method of methylation for the determination of urinary S-benzyl-N-acetylcysteine (benzylmercapturic acid, SBAC), a metabolite of toluene, by gas chromatography (GC) was developed. Acidified urine samples (pH 2) were extracted once with ethyl acetate and then derivatized to methyl ester (ME) using HCl-methanol. The optimum conditions for derivatization for SBAC and the internal standard (S-phenethyl-N-acetylcysteine) were reaction at 60 degrees C for 20 min. The SBAC-ME was measured by capillary GC. The calibration curve showed good linearity over the range of 0.2 to 5.0 mg/L (r = 0.986). This method was compared with a previously developed diazomethane methylation method for testing urine from subjects who had sniffed toluene. The values obtained by the two different methods were in good accordance. These results suggest that this technique for the methylation of SBAC by means of HCI-methanol is simpler and time-saving, thus making it feasible to determine SBAC and other mercapturic acids in urinary samples obtained from subjects who have been exposed to organic solvents.     

Cytochrome P 450 2C9 phenotyping using low-dose tolbutamide

Objectives The hypoglycaemic drug tolbutamide is used for assessment of CYP2C9 activity in vivo. However, therapeutically active doses of 500 mg bear the risk of hypoglycaemia, and a tolbutamide-derived parameter based on a single plasma or urine concentration reflecting CYP2C9 activity accurately is lacking.Methods We examined tolbutamide and its metabolites 4-hydroxy-tolbutamide and carboxytolbutamide in plasma and urine of 26 healthy, male volunteers up to 24 h after intake of 125 mg tolbutamide using liquid chromatography–tandem mass spectrometry. CYP2C9 genotypes were determined by sequencing of exons 3 and 7. Raw plasma and urine data were compared with pharmacokinetic parameters, CYP2C9 genotypes, and data from a study in 23 volunteers with all six CYP2C9*1–*3 combinations who received 500 mg tolbutamide.Results Plasma clearance and tolbutamide plasma concentrations 24 h after drug intake reflected the genotypes: 0.85 l/h and 1.70 µg/ml (95% confidence interval, CI, 0.80–0.89 l/h and 1.50–1.90 µg/ml) for CYP2C9*1 homozygotes (n=15), 0.77 l/h and 2.14 µg/ml (95%CI, 0.67–0.88 l/h and 1.64–2.63 µg/ml) for *1/*2 genotypes (n=7), 0.60 l/h and 3.13 µg/ml (95%CI, 0.58–0.62 l/h and 2.68–3.58 µg/ml) for *1/*3 genotypes (n=3), and 0.57 l/h and 3.27 µg/ml in the single *2/*2 carrier. Natural logarithms of tolbutamide plasma concentrations 24 h after intake correlated to plasma clearance (r²=0.84, P<0.0000001). This correlation was confirmed in the comparison data set (r²=0.97, P<0.0000001).Conclusions A low dose of 125 mg tolbutamide can safely and accurately be used for CYP2C9 phenotyping. As a simple metric for CYP2C9 activity, we propose to determine tolbutamide in plasma 24 h after drug intake.     

Stereoselective Disposition of Ibuprofen Enantiomers in the Isolated Perfused Rat Kidney

The renal clearance of ibuprofen enantiomer was studied separately in the isolated perfused rat kidney at initial perfusate concentrations of 10 µg/ml (n = 4) and 100 µg/ml (n = 4). Perfusate and urine samples were measured for R(–) and S( + )-ibuprofen using a stereospecific HPLC assay; urine samples were also analyzed after alkaline hydrolysis. Functional viability of the kidney was assured by determining the fractional excretion of glucose and glomerular filtration rate (GFR) at similar perfusion pressures. The clearance of ibuprofen was equivalent to the apparent formation clearance of conjugated enantiomer since unchanged ibuprofen could not be detected in the urine. At 10 and 100 µg/ml, the clearance (±SD) of R(–)-ibuprofen was 2.50 ± 1.28 and 2.19 ± 1.42 µl/min, respectively. At 100 µg/ml, the clearance of S( + )-ibuprofen was 0.805 ± 0.290 µl/min. The protein binding of ibuprofen was found to be concentration dependent and favored the R(–)-enantiomer. The excretion ratio (clearance corrected for free fraction and GFR) of R(–)-ibuprofen was 0.398 ± 0.209 and 0.295 ± 0.209 for perfusate concentrations of 10 and 100 µg/ml, respectively. The excretion ratio of S( + )-ibuprofen was 0.0886 ± 0.0335 for perfusate concentrations of 100 µg/ml. These results demonstrate that the sum of renal mechanisms involved for the clearance of R(–)- and S( + )-ibuprofen was net reabsorption. Ibuprofen was recovered in the urine solely as conjugated material and no evidence of R(–) to S( + ) conversion was observed. In addition, the data suggest that R(–)-ibuprofen is cleared through the kidney faster than its S( + )-enantiomer.     

Identification of the n-heptane metabolites in rat and human urine

Numerous n-heptane metabolites have been identified and quantified by gas chromatography and mass spectrometry in some tissues and in the urine of Sprague Dawley rats exposed for 6 h to 1800 ppm n-heptane. 2-Heptanol and 3-heptanol were the main biotransformation products of the solvent. 2-Heptanone, 3-heptanone, 4-heptanol, 2,5-heptanedione, -valerolactone, 2-ethyl-5-methyl-2, 3-dihydrofuran and 2,6-dimethyl-2,5-dihydropyran were also found as metabolites of n-heptane. In five shoe factory workers and in three rubber factory workers the mean exposure to technical heptane was measured (n-heptane ranged between 5 and 196 mg/m³). In the urine collected at the end of their work shift some n-heptane biotransformation products were found: 2-heptanol, 3-heptanol, 2-heptanone, 4-heptanone and 2,5-heptanedione. 2-Heptanol was the main n-heptane metabolite and its urinary concentrations ranged between 0.1 and 1.9 mg/l. Urinary 2,5-heptanedione was detectable only in some samples and at very low concentration (0.1–0.4 mg/1).These data suggest that n-heptane can be considered as a neurotoxic product, since it gives rise to 2,5-heptanedione, but the small amount of the urinary metabolite is very unlikely to cause clinical damage to the peripheral nervous system.Part of this work was presented at the 48 Congr. Naz. Soc. Ital. Med. Lav. Igiene Ind. Pavia 18–21 September 1985     

Development and validation of a fast ultra-high-performance liquid chromatography tandem mass spectrometry method for determining carbonic anhydrase inhibitors and their metabolites in urine and hair

A new, rapid, sensitive, and comprehensive ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC–MS/MS) method for quantifying diuretics (acetazolamide, brinzolamide, dorzolamide, and their metabolites) in human urine and hair was developed and fully validated. Twenty-five milligrams of hair were incubated with 500-μl M3® buffer reagent at 100°C for 1 h for complete digestion. After cooling, 1-μl supernatant was injected onto chromatography system. Urine samples were simply diluted before injection. The chromatographic run time was short (8 min) through a column with a mobile phase gradient. The method was linear (determination coefficients always higher than 0.99) from limit of quantification (LOQ) to 500 ng/ml in urine and from LOQ to 10 ng/mg in hair. LOQs ranged from 0.07 to 1.16 ng/ml in urine and from 0.02 to 0.15 ng/mg in hair. No significant ion suppression due to matrix effect was observed, and process efficiency was always higher than 80%. Intra- and inter-assay precision was lower than 15%. The suitability of the methods was tested with six urine and hair specimens from patients treated with acetazolamide, dorzolamide, or brinzolamide for ocular diseases or systemic hypertension. Average urine concentrations were 266.32 ng/ml for dorzolamide and 47.61 ng/ml for N-deethyl-dorzolamide (n = 3), 109.27 ng/ml for brinzolamide and 1.02 ng/ml for O-desmethyl-brinzolamide (n = 2), and finally, 12.63 ng/ml for acetazolamide. Average hair concentrations were 5.94 ng/mg for dorzolamide and 0.048 ng/mg for N-deethyl-dorzolamide (n = 3), 3.26 ng/mg for brinzolamide (n = 2), and 2.3 ng/mg for acetazolamide (n = 1). The developed method was simple and fast both in the extraction procedures making it eligible in high-throughput analysis for clinical forensic and doping purposes.     

Pharmacokinetics of the active metabolite of the prodrug repirinast in healthy Caucasian volunteers after a single oral dose

Summary The pharmacokinetics of BAY w 8199, the active metabolite of the prodrug repirinast (BAY u 2372), has been investigated after oral administration of 150, 300 and 450 mg repirinast to twelve healthy male Caucasians.Plasma BAY w 8199 concentrations were very variable between subjects. The mean peak level (geom. mean; 1s-range) was 0.14 (0.08–0.25), 0.19 (0.13–0.29) and 0.24 (0.14–0.42) mg/l after the 150, 300 and 450 mg doses, respectively. Peak levels were reached 0.5–2.5 h after drug intake. Terminal half-lives were calculated as 5.9 h (150 mg), 8.0 h (300 mg) and 9.8 h (450 mg).The dose proportionality of the plasma profiles of BAY w 8199 and of its excretion in urine was demonstrated by testing several parameters.About 7.4% of each dose (calculated as BAY w 8199) was excreted in urine over 36 h. The renal clearance of about 27 l/h suggests that BAY w 8199 is excreted by tubular secretion in addition to glomerular filtration.Abbreviations C_max maximum plasma concentration - C_max,norm dose and body weight normalized; C_max - C'(n) concentration calculated for time t_n from a log-linear regression line - t_max time of the maximum plasma concentration - AUC area under the curve from t=0 to infinity - AUC(0–12) area under the curve from t=0 to t=12 hours - AUC(0–t_n) area under the curve from t=0 to the last data point - AUC(t_n–) area under the curve extrapolated from t_n to infinity - AUC_norm dose and body weight normalized AUC-values - t_1/Z terminal half-life - Ae amount excreted into urine - CL_R renal clearance     

Urinary excretion of N-acetyl-S-allyl-L-cysteine upon garlic consumption by human volunteers

  N-Acetyl-S-allyl-L-cysteine (allylmercapturic acid, ALMA) was previously detected in urine from humans consuming garlic. Exposure of rats to allyl halides is also known to lead to excretion of ALMA in urine. ALMA is a potential biomarker for exposure assessment of workers exposed to allyl halides. It is not known whether garlic consumption can lead to urinary concentrations of ALMA which may interfere with biological monitoring of exposure to allyl halides by determination of urinary ALMA. Therefore, this study was undertaken to determine the cumulative excretion and the excretion kinetics of ALMA in urine of humans consuming garlic. Six human volunteers were given orally two garlic tablets, each containing 100 mg garlic extract (each representing 300 mg fresh garlic). Three of the volunteers consumed additional garlic after the garlic tablet intake. Urine samples were collected up to 24 h after the intake of the garlic tablets. ALMA was identified in the urine using gas chromatography-mass spectrometry (GC-MS) and determined quantitatively with a limit of detection of 0.10 μg/ml with gas chromatography with sulphur selective detection. The total amount of ALMA found in urine of volunteers who consumed two garlic tablets was 0.43±0.14 mg (n=3). In the urine of the three volunteers who consumed not only two garlic tablets but also additional fresh garlic, a significantly higher amount of ALMA was excreted in the urine, 1.4±0.2 mg (n=3). The elimination half-life of ALMA, estimated from urinary excretion rate versus time curves, was 6.0±1.3 h (n=5). One volunteer, who ate additional garlic, showed an irregular elimination profile and was excluded from this estimation. The highest urinary concentration of ALMA found in this study was 2.2 μg/ml. In a preliminary biological monitoring study of exposure in workers with potential exposure to allyl chloride (AC) up to the occupational exposure limit of 1 ppm (8-h TWA), we recently found urinary ALMA concentrations up to 4 μg/ml. Based on the results presented here, we conclude that garlic consumption is a potential confounder when monitoring human exposure to allylhalides and other chemicals leading to ALMA excretion when ALMA is used as a biomarker of exposure. Received: 17 November 1995/Accepted: 14 February 1996     

The pharmacokinetics of eflornithine (α-difluoromethylornithine) in patients with late-stage <Emphasis Type="Italic">T.b. gambiense</Emphasis> sleeping sickness

Objective To investigate the plasma, cerebrospinal fluid (CSF) levels and pharmacokinetics of eflornithine (DFMO) in patients with late-stage T.b. gambiense sleeping sickness who were treated with an oral DFMO at 100 mg/kg or 125 mg/kg body weight every 6 h for 14 days.Methods Plasma and CSF concentrations of DFMO were measured during day 10 and day 15 in patients following oral DFMO at 100 mg/kg (group I: n=12) and 125 mg/kg (group II: n=13) body weight every 6 h for 14 days. Clinical and parasitological assessments were performed at 24 h after the last dose of DFMO and at 12 months.Results Patients in each group had a good initial response, but relapse was observed in six patients (three patients for each group) during 12 months follow-up. Plasma DFMO concentrations did not increase proportionally to doses when the dose increased from 100 mg/kg to 125 mg/kg body weight given every 6 h (60–70% of the expected increase). In most cases, concentration–time profiles of DFMO in each group were best fit using a two-compartment open model with first-order input, with absorption lag-time and first-order elimination. Average trough (C_ss-min) and average (C_ss-ave) plasma DFMO concentrations during steady state varied between 189–448 nmol/ml and 234–528 nmol/ml, following 100 mg/kg and 125 mg/kg dose group, respectively. C_max, t_max and AUC_0– values following the last dose were 296–691 nmol/l, 2–3 h, and 2911–6286 nmol h/ml, respectively. V_z/F, CL/F and t_1/2z values were 0.47–2.66 l/kg, 0.064–0.156 l/h/kg, and 3.0–16.3 h, respectively. CSF concentrations at steady state varied between 22.3 nmol/ml and 64.7 nmol/ml. Patients who had treatment failure tended to have lower plasma and CSF DFMO concentrations than those who had successful treatment.Conclusion Oral DFMO at the dose of 125 mg/kg body weight given every 6 h for 14 days may not produce adequate therapeutic plasma and CSF levels for patients with late-stage T.b. gambiense sleeping sickness.     

Urinalysis for detection of chemically induced renal damage (3) — establishment and application of radioimmunoassay for lysozyme of rat urine

The radioimmunoassay (RIA) as a high sensitive detection method for rat lysozyme (LZM) was established and applied to determine LZM excretion in urine from rats treated with tubulotoxic chemicals in order to establish a sensitive method of detecting minor renal damage. Rat LZM which showed a single protein band on sodium dodecylsulfate polyacrylamide gel electrophoresis was purified by ion-exchange chromatography and gel filtration. The assay sensitivity of the established RIA using the purified rat LZM was 4–256 ng/ml rat LZM and was about 20 times the turbidity method. The concentration of LZM in normal rat urine was 76.2±6.0 ng/ml (mean ± SE, n = 50) using the RIA. In urine containing more than 100 ng/ml LZM, a high correlation between the values determined by the RIA and those by the turbidity method was observed. However, egg white LZM, human urinary LZM and guinea pig urinary LZM were not detectable by the RIA. Using the RIA, it was ascertained that urinary LZM excretion began to increase on day 5 in rats treated with gentamicin (15 or 30 mg/kg/day sc for 17 days), during the 6–9 h period in the rats treated with mercuric chloride (1 mg/kg sc), and during the 0–3 h period in the rats treated with p-aminophenol (1 mmol/kg sc). These significant increases in LZM excretion were not detectable by the turbidity method; therefore, it was concluded that this RIA for rat LZM was very useful for detection of minor renal damage.     

Individualized aminophylline therapy in patients with obstructive airway disease: Oral dosage prediction from an intravenous test dose

Summary Theophylline disposition after an intravenous test dose of aminophylline was determined in 83 subjects: 7 patients with and 58 without congestive heart failure (CHF), and 18 healthy controls. Based on the pharmacokinetics of theophylline in the individual, the oral dosage of aminophylline was scheduled to attain steady-state trough theophylline concentrations (C_pred) near the therapeutic margin. Significant differences in theophylline clearance with a relatively constant volume of distribution were observed between various groups divided by age, smoking habit and CHF; the significantly different (p<0.001) mean clearance values were: 0.042±0.0161/h/kg (mean ± SD) in patients without CHF (n=58) as opposed to 0.016±0.001 l/h/kg in patients with CHF(n=7), 0.038±0.013 l/h/kg in non-smokers (n=59) versus 0.054±0.015 l/h/kg in smoking subjects (n=17), and 0.030±0.010 l/h/kg in elderly (>60 years) non-smoking patients (n=7) versus 0.057±0.017 l/h/kg in smoking patients (n=5) aged 40 to 59 years. No gender-related difference was detected in theophylline disposition. For all subjects together (n=83), there was no significant correlation between age and clearance (r=-0.111, p>0.1). The multivariate analysis indicated that the overall variability in theophylline clearance was affected first by the smoking habit (t=4.960; p<0.001) and second by CHF (t=-3.052; p<0.001), but not by age (t=1.140) or by sex (t=0.069). 78% of the patients who did not have CHF required a daily dose of aminophylline of 600 to 900 mg, whereas a dose of 300 to 450 mg was the rule in patients with CHF. The measured steady-state minimum concentration (C_meas) ranged from 5.4 to 14.6 µg/ml (9.0±2.2 µg/ml: mean ± SD) which was in good agreement with the C_pred (5.6 to 13.6, 9.0±1.6 µg/ml) in all patients (n=60) who received the oral dose of aminophylline calculated from the test dose. The overall prediction error was -0.08±1.83 µg/ml (–1.42±19.90%); only 3 of 60 measurements were found to be outside±2 SD. It is concluded that using a test dose to individualize aminophylline therapy is likely to remain the most reliable means to assure the maximum therapeutic benefit in patients with airway obstruction.A preliminary account of this study was presented at the Eighth International Congress of Pharmacology, Tokyo, July 19–24, 1981     

Pharmacokinetics of nicorandil in patients with normal and impaired renal function

Summary The pharmacokinetics of oral nicorandil 20 mg 12 hourly for 9 doses was evaluated in 21 hospitalized patients with angina pectoris due to coronary heart disease and with normal and impaired renal function. Patients were divided into 3 groups based on creatinine clearance (CL_Cr): GROUP I (n=6) > 80 ml/min, GROUP II (n=8) 20–80 ml/min, and GROUP III (n=7) < 20 ml/min.After the first dose, the total clearance of nicorandil (CL) value did not change with increasing renal failure and so was not dependent on creatinine clearance. After the last dose CL was 51 l·h^–1 in Group I, 44 l·h^–1 in Group II and 56 l·h^–1 in Group III, and it was not related to creatinine clearance. The percentage of the dose excreted in the urine was 0.4%. No significant difference was noted in any of the other pharmacokinetic parameters examined in the three groups, not even on comparing values obtained on the first and last days of treatment.The findings suggest that there is no need to change the dose of nicorandil in subjects with different degrees of renal failure.     

Elimination profiles of prednisone and prednisolone after different administration routes: Evaluation of the reporting level and washout periods to ensure safe therapeutic administrations

Prednisolone (PRED) and prednisone (PSONE) are prohibited in sports competitions when administered by systemic routes, and they are allowed by other routes for therapeutic purposes. There is no restriction of use in out-of-competition periods. The present study aimed to evaluate the urinary excretion of PRED, PSONE, and their most important metabolites after systemic and nonsystemic treatments in order to verify the suitability of the current reporting level of 30 ng/ml used to distinguish allowed and prohibited administrations and to establish washout periods for oral treatments performed in out-of-competition periods. PRED was studied after dermatological administration (5 mg/day for 5 days, n = 6 males) and oral administration (5 mg, n = 6 males; 10 mg, n = 2 males). PSONE was studied after oral administration (10 mg, n = 2 males; 30 mg, n = 1 male and 1 female). Concentrations in urine were measured using an LC–MS/MS method. Concentrations after dermatological treatment were low for all metabolites. After oral administration, concentrations were very high during the first 24 h after administration ranging from 1.6 to 2261 ng/ml and from 4.6 to 908 ng/ml for PRED and PSONE, respectively. Concentrations of most of the metabolites measured were lower than 30 ng/ml from 24 h after all oral administrations. New reporting levels are proposed for PRED and PSONE considering data of our study and other information published after nonsystemic administrations of the compounds. Washout periods of at least 24 h are recommended to ensure no false positives when oral treatments need to be performed in out-of-competition periods.     

S-p -Toluylmercapturic acid in the urine of workers exposed to toluene: a new biomarker for toluene exposure

A mercapturic acid attached to the aromatic ring of toluene was for the first time detected in human urine as a metabolite of toluene. Since the metabolism of toluene is usually considered to take place at the side-chain, this gives, besides the biosynthesis of cresols, a further hint of a metabolic conversion of the aromatic system. We examined a group of 33 workers occupationally exposed to toluene, determining the concentrations of toluene in ambient air and in whole blood, o-cresol and hippuric acid in urine and p-toluylmercapturic acid (p-TMA) in urine. All blood and urine samples were collected post-shift. The renal excretion of S-p-toluylmercapturic acid showed highly significant correlations with established parameters of a biological monitoring of toluene. The median ambient air concentration was 63 ppm, ranging from 13 to 151 ppm, the median concentration of toluene in whole blood was 804 μg/l, corresponding to median urinary concentrations for o-cresol of 2.3 mg/l, hippuric acid of 2.3 g/l and p-TMA of 20.4 μg/l. p-TMA was not detectable in urine samples of a control group of 10 non-exposed persons. Both the German Biological Tolerance Values (BAT-values) for toluene in blood (1000 μg/l) and o-cresol in urine (3 mg/l) correspond to a mean p-TMA elimination of ∼50 g/l, and thus are in agreement with each other. According to our results p-TMA reflects internal toluene exposure diagnostically sensitive and specifical. With the developed analytical procedure we determined a median benzylmercapturic acid (BMA) concentration of 190 μg/l in the urine samples of the toluene exposed persons. We also determined a median BMA concentration of 30 μg/l in the control samples of non-exposed persons. However, these results are preliminary and require further confirmation as the reliability of the method was determined only for p-TMA. Received: 15 July 1997 / Accepted: 24 September 1997     

Kinetics of cotinine after oral and intravenous administration to man

Summary Cotinine, the main metabolite of nicotine, was administered intravenously to healthy male non-smoking volunteers in doses of 5, 10 and 20 mg, and orally in doses of 10 and 20 mg.Intravenous administration was characterized by a dose-independent half-life of 12.2 h, mean residence time of 15.9 h, total clearance of 3.64 l h^–1 and a volume of distribution of 56.5 l. Renal clearance was 0.46 l h^–1 and approximately 12.0% of the dose was excreted unchanged in the urine. The mean absorption time after oral dosing ranged between 1 and 3 h, the peak concentration was reached within 45 min and the mean elimination half-lives were 12.9 and 11.7 h, respectively, after the 10 and 20 mg doses. Systemic bioavailability ranged between 0.84 and 1.11 following 10 mg and between 0.97 and 1.03 following the 20 mg dose. Mean urinary recovery and renal clearance were almost identical with the values after iv administration.     

Pharmacokinetics of methadone during maintenance treatment: Adaptive changes during the induction phase

Summary Deuterated methadone (M-d₃0) and GC-MS were used to study the pharmacokinetics of methadone (M) during the induction stage of methadone maintenance treatment (MMT). A pulse dose of M-d₃ was given on Days 1 and 25 of two dosage regimens, one with a continuous 30 mg dose (n=6), and the other with 30 mg for 10 days, followed by 60 mg as the maintenance dose (n=6). Plasma and urinary levels of M and M-d₃ were measured throughout and plasma half-lives, oral bioavailabilities and volumes of distribution were calculated from the data of Days 1–2 and 24–26. The oral bioavailability of a methadone solution was found to be between 81 and 95%; elimination half-life in the -phase varied between 19 and 58 h; the volume of distribution was 4.1±0.65 l/kg; and total body clearance of M was 54–195 ml/min and its renal clearance 3.4–34 ml/min. A consistent finding was a lower urinary pH and increased renal clearance during the first days of MMT as compared with after one month. In 4/12 of the patients dispositional tolerance was developed to methadone during the first month of treatment. The shorter elimination half-lives in those patients probably caused unacceptably high fluctuation in the body content of M during the 24 h dosage interval, and may have interfered therefore, with its therapeutic effectiveness     

Pharmacokinetics of the oral narcotic analgesic bezitramide and preliminary observations on its effect on experimentally induced pain

Summary The oral absorption of bezitramide 5 mg was studied in 7 human volunteers, using a specific radioimmuno-assay which measured both bezitramide and its active metabolite R-4618. A lag time of 0.5–1.0 h and a C_max of 5.4 ng/ml plasma were found, the latter occurring 2.5–3.5 h after administration. The apparent elimination half-life varied from 11 to 24 h. Less than 0.3% of the dose was excreted unchanged in the urine. High concentrations in the faeces of some individuals indicate incomplete absorption and/or biliary secretion. The analgesic effect, using a standardized superficial electrical stimulation method, reached its maximum between 2.5 and 3.5 h after dosing, in accordance with the absorption phase. The duration of the effect was highly variable. Experiments in rats (n=6,³H-bezitramide 2.5 µg), demonstrated extensive biliary excretion (up to 70% of total radioactivity) and less than 3% of the label was removed by urinary excretion.     

The effect of St. John's wort on the pharmacokinetics, metabolism and biliary excretion of finasteride and its metabolites in healthy men

The aim of this study was to investigate what the consequences of induced drug metabolism, caused by St. John's wort (SJW, Hypericum perforatum) treatment, would have on the plasma, biliary and urinary pharmacokinetics of finasteride and its two previously identified phase I metabolites (hydroxy-finasteride and carboxy-finasteride). Twelve healthy men were administered 5 mg finasteride directly to the intestine via a catheter with a multi-channel tubing system, Loc-I-Gut, before and after 14 days SJW (300 mg b.i.d, hyperforin 4%) treatment. Bile samples were withdrawn via the Loc-I-Gut device from the proximal jejunum. LC–ESI-MS/MS was used to analyze finasteride and its metabolites in plasma, bile and urine. HPLC-UV was used to analyze hyperforin in plasma. The herbal treatment significantly reduced the peak plasma concentration (C_max), the area under the plasma concentration–time curve (AUC_0–24h) and the elimination half-life (t_1/2) of finasteride. The geometric mean ratios (90% CI) were 0.42 (0.36–0.49), 0.66 (0.56–0.79) and 0.54 (0.48–0.61), respectively. Finasteride was excreted unchanged to a minor extent into bile and urine. Hydroxy-finasteride was not detected in plasma, bile or urine. Carboxy-finasteride was quantified in all three compartments and its plasma pharmacokinetics was significantly affected by SJW treatment. Hyperforin concentration in plasma was 21 ± 7 ng/ml approximately 12 h after the last dose of the 14 days SJW treatment. In conclusion, SJW treatment for 2 weeks induced the metabolism of finasteride and caused a reduced plasma exposure of the drug. New knowledge was gained about the biliary and urinary excretion or the drug and its metabolites.     

Pharmacodynamics and kinetics of etozolin/ozolinone in hypertensive patients with normal and impaired kidney function

Summary The effect on urinary electrolyte excretion, renin release and plasma norepinephrine of single oral doses of 400 mg etozolin (E) and of 40 mg furosemide (F) were studied in hypertensive patients with normal (n=6) and impaired kidney function (n=6). E caused a marked saluresis up to 24 hours, showing its long duration of action. F, however, displayed a brief, brisk peak diuresis, followed by a rebound from the 4th to the 24th hours. The brisk peak diuresis induced by F was associated with pronounced release of renin, almost twice that induced by E. In chronic renal failure the renin release in relation to the magnitude of the diuresis was increased, i.e. the sensitivity of these patients to changes in water homeostasis was increased. E and F stimulated the sympathetic system to roughly the same extent. Patients with essential hypertension had higher plasma levels of norepinephrine than hypertensive patients with chronic renal failure. In addition, hypertensive patients with normal renal function (n=4) and varying degrees of renal impairment (n=11) were also given 400 mg daily for 2 weeks. Effects on blood pressure and electrolyte homeostasis were monitored, as well as the plasma kinetics of metabolite I, ozolinone. At the end of the 2 week treatment E had significantly lowered systolic (–12 mm Hg) and diastolic (–9 mm Hg) blood pressure, and had produced a significant loss of body weight, without altering plasma electrolytes or blood chemistry. There was no accumulation of the effective metabolite ozolinone under conditions of severe impairment of kidney function. It is concluded that E can effectively control high blood pressure in patients with normal and impaired kidney function. Its effective metabolite ozolinone did not accumulate in chronic renal failure.     

Taurine,a possible urinary marker of liver damage: a study of taurine excretion in carbon tetrachloride-treated rats

Carbon tetrachloride (CCl₄) caused a dose-dependent increase in urinary taurine which correlated with both the histological and biochemical assessment of liver damage. The peak elevation in urinary taurine occurred within the first 48 h after dosing but there was still significant taurinuria 72 and 96 h after the intermediate dose (1 ml.kg^–1) and highest dose (2 ml.kg^–1), respectively. Levels of taurine in serum were also elevated over the 24 h period following a hepatotoxic dose (2 ml.kg^–1) of CCl₄. In contrast, although initially elevated, levels of taurine in the liver declined over the 24 h period following dosing and were significantly lower 96 h after a hepatotoxic dose of CCl₄ (2 ml.kg^–1). Male rats showed a different urinary profile for taurine than female rats after dosing with CCl₄. A reduction in food intake seemed to lower urinary taurine levels although these changes were not statistically significant. There was a significant correlation between the level of urinary taurine and the level of serum AST for individual animals given a hepatotoxic dose of CCl₄ (2 ml.kg^–1). The data presented suggest that: i) taurine is produced by the liver in response to a toxic insult and subsequent leakage from damaged cells leads to increased levels in the urine; ii) the urinary taurine level may be a useful non-invasive marker of liver damage.     

Assay of the major (4-hydroxylated) metabolites of diphenylhydantoin in human urine

Summary A modified gas chromatographic procedure for the determination of unconjugated and conjugated 4-hydroxydiphenylhydantoin (4-OH-DPH) in urine has been developed.Unconjugated 4-OH-DPH is determined after selective extraction with toluene — ether (1:1). For the assay of conjugated 4-OH-DPH, the urine is pre-extracted withisoamylalcohol before acid hydrolysis to avoid interference by the dihydrodiol metabolite of DPH. The sensitivity of the method is 0.1 µg per ml. The method has been used to determine the urinary metabolites in two adult volunteers, during steady state plasma concentrations of DPH and in the elimination phase.To the memory of Balzar Alexanderson