Urinary excretion of phenobarbitone and its metabolites in chronically treated patients

The elimination of phenobarbitone (PB) was studied in 14 chronically treated epileptic patients under steady state conditions. PB, [S]-PB-N-glucoside ([S]-PB-N-G) and p-hydroxy-PB (p-OH-PB) were assayed in urine by a HPLC method.Some 57 % of the daily dose was recovered in urine, 14 % as [S]-PB-N-G, 16 % as p-OH-PB (conjugated plus non-conjugated) and 27 % as unaltered PB.Thus PB-N-G formation contributed significantly to the elimination of PB during long-term administration of the drug, and there was reason to suspect that some of the PB-N-G formed may have already been degraded to untraced products before excretion from the body.     

Urinary excretion of valproate and some metabolites in chronically treated patients

Urinary excretion of the antiepileptic agent valproic acid (VPA) and major metabolites from its glucuronidation, beta-oxidation, and omega- and omega 1-hydroxylation pathways were studied under steady state conditions in 24 epileptic patients. Some 55 +/- 18% (SD) of the daily dose was recovered in urine, 33 +/- 14% in the form of VPA-glucuronide, 15 +/- 8% as beta-oxidation products, and 4 +/- 2% and 2 +/- 1% as products of the omega- and omega 1-hydroxylation pathways, respectively. Only 1 +/- 2% of the dose was excreted unchanged. The proportion metabolized by direct glucuronidation tended to increase with dose at the expense of the oxidative pathways, particularly beta-oxidation. However, the wide variation in the patterns of urinary metabolite excretion precludes use of routinely collected urinary excretion data as a basis for detecting any but severe noncomplicance with VPA therapy or abnormalities of VPA metabolism.     

Urinary excretion of acrylonitrile and its metabolites in rats

Quantitative analysis of the dose-dependent urinary excretion of acrylonitrile and its metabolites was carried out in male Wistar rats following inhalation exposure of the animals to 1, 5, 10, 50 and 100 ppm acrylonitrile for 8 h. Quantitative analysis of acrylonitrile in urine was performed by gas chromatography. The urinary metabolites cyanoethyl mercapturic acid, S-carboxymethyl cysteine and hydroxyethyl mercapturic acid were measured by a modified amino acid analysis, and thiodiglycolic acid by GC-MS. The excretion pattern of the compound and its metabolites was dependent on the exposure level; it is concluded that urinary determination of the unmetabolized acrylonitrile and two of its metabolites, cyanoethyl mercapturic acid and thioglycolic acid, may be useful for biological monitoring of industrial exposure.     

Urinary excretion of methylparaben and its metabolites in preterm infants

A high-performance liquid chromatographic (HPLC) assay to quantitate methylparaben in urine was developed. Standard curves were linear and recovery of the paraben from urine averaged 82.6%. The urinary excretion of methylparaben in six preterm infants (less than or equal to 31 weeks gestational age), who were receiving intramuscular injections of a paraben-containing gentamicin formulation, ranged from 13.2 to 88.1%. Small quantities of the metabolite, p-hydroxybenzoic acid, were detected by GC-MS.     

Urinary excretion of digoxin and its metabolites in hyperacidic patients and in patients during coronary care

The hydrolytic cleavage of digoxin was studied after single oral doses of tritiated glycoside to four patients with gastric hyperacidity (GH-group) and to six patients during coronary care (CCU-group). Drug analysis was performed with a high-pressure liquid chromatographic method. Results in the two groups did not differ and were similar to results in a previous study in healthy volunteers. On the average 22% of the radioactivity was recovered in 24-h urine specimen. Of this 24.8 +/- 8.5% (GH-group, mean +/- SEM) and 19.3 +/- 6.6% (CCU-group) were cleavage products and unidentified, polar metabolites in equal amounts. This indicates that hydrolysis of digoxin is on average limited even in patients at risk for such metabolic cleavage.     

Urinary excretion of n-hexane metabolites

Exposure to n-hexane, a component of many industrial solvent mixtures, is known to cause polyneuropathy in man. The concentration of metabolites in urine following exposure may be useful in biological monitoring. In a comparative study experimental animals (rat, rabbit and monkey) were subjected to single inhalatory treatments of 6, 12 and 24 h with 5,000 ppm of pure n-hexane. At the end of the treatments and at intervals thereafter, urine, and in rats also blood, were collected and analyzed for n-hexane and its metabolites. While the urine of rats contained 2-hexanol, 3-hexanol, methyl n-butyl ketone, 2,5-dimethylfuran, -valerolactone and 2,5-hexanedione, rabbit and monkey urine were found to contain only 2-hexanol, 3-hexanol, methyl n-butyl ketone and 2,5-hexanedione. Within 72 h of the end of exposure, the principal metabolite was 2,5-dimethylfuran in rats and 2-hexanol in rabbits and monkeys. In all three species the excretion rates of methyl n-butyl ketone, 3-hexanol and 2-hexanol peaked several hours earlier than 2,5-hexanedione (and -valerolactone and 2,5-dimethylfuran in rats). In all species 2,5-hexanedione was still detectable in urine 60 h following exposure. n-Hexane metabolites in rat blood were 2-hexanol, methyl-n-butyl ketone, 2,5-dimethylfuran and 2,5-hexanedione. The first two, as well as n-hexane itself, were found in maximum concentration immediately after termination of exposure, while 2,5-dimethylfuran and 2,5-hexanedione, with the longer exposure times, peaked some hours later. The data from urine collected at the end of exposure were compared with those obtained in a parallel study in humans occupationally exposed to a mixture of hexane isomers. Humans chronically exposed to 10–140 ppm n-hexane had 2,5-hexanedione concentrations in urine ranging from 0.4 to 21.7 mg/l, i.e., in the same proportion as rats exposed once for 6 or 12 h to 5,000 ppm.     

Urinary cyclophosphamide excretion in rats after intratracheal, dermal, oral and intravenous administration of cyclophosphamide

The urinary excretion of unmetabolized cyclophosphamide was studied in rats after intratracheal, dermal, oral and intravenous administration. Rats were given two doses of 1 mg kg-1 cyclophosphamide 48 h apart and urine was collected for 96 h after the first treatment. With the help of a phosphor-specific filter in a flame photometer attached to a gas chromatograph, low levels of cyclophosphamide were determined after derivatization with trifluoroacetic anhydride. Cumulative excretion as a percentage of dose ranged from 4.0 to 6.9 after the first dose and 2.7 to 5.5 after the second dose. The highest rate of excretion after the second administration was observed in rats treated intratracheally, while cumulative excretion was higher (6.9%) after the first than after the second (2.7%) intravenous treatment. The most prolonged excretion was observed after dermal application.     

Stability of thioTEPA and its metabolites, TEPA, monochloroTEPA and thioTEPA-mercapturate, in plasma and urine

The degradation of N,N′,N′′-triethylenethiophosphoramide (thioTEPA) and its metabolites N,N′,N′′-triethylenephosphoramide (TEPA), N,N′-diethylene,N′′-2-chloroethylphosphoramide (monochloroTEPA) and thioTEPA-mercapturate in plasma and urine has been investigated. ThioTEPA, TEPA and monochloroTEPA were analyzed using a gas chromatographic (GC) system with selective nitrogen/phosphorous detection; thioTEPA-mercapturate was analyzed on a liquid chromatography-mass spectrometric (LC-MS) system. The influences of pH and temperature on the stability of thioTEPA and its metabolites were studied. An increase in degradation rate was observed with decreasing pH as measured for all studied metabolites. In urine the rate of degradation at 37°C was approximately 2.5±1 times higher than at 22°C. At 37°C thioTEPA and TEPA were more stable in plasma than in urine, with half lives ranging from 9–20 h for urine and 13–34 h for plasma at pH 6. Mono- and dichloro derivatives of thioTEPA were formed in urine and the monochloro derivative was found in plasma. Degradation of TEPA in plasma and urine resulted in the formation of monochloroTEPA. During the degradation of TEPA in plasma also the methoxy derivative of TEPA was formed as a consequence of the applied procedure. The monochloro derivative of thioTEPA-mercapturate was formed in urine, whereas for monochloroTEPA no degradation products could be detected.     

Urinary excretion of probenecid and its metabolites in humans as a function of dose.

A GLC assay was used to study the excretion of probenecid and its metabolites in the urine of human subjects following oral doses of 0.5, 1, and 2 g. From 75 to 88% of the dose was found in the urine. The major metabolite, probenecid acyl glucuronide, accounted for 34-47% of the dose. Approximately equal amounts (10-15%) of the mono-N-propyl, secondary alcohol, and carboxylic acid metabolites were excreted in the unconjugated from with only traces in the conjugated form. The primary alcohol metabolite was not found in measurable amounts. The terminal half-lives for excretion of all metabolites were in the range of 4-6 hr, were independent of dose, and were limited by their rates of formation. A prolonged time course of excretion of the metabolites, particularly at higher doses, suggests that probenecid, being poorly soluble in water, precipitates from solution in the GI tract, forming a depot of drug from which absorption is dissolution rate limited. The urinary excretion of unchanged probenecid, which accounts for 4-13% of the dose, is dependent on both the pH and flow rate of urine.     

Urinary and biliary excretion of metabolites of halothane in dogs.

To determine the urinary and biliary excretion of metabolites of halothane in dogs, 12 beagles were anesthetized with halothane either at 0.5 MAC (minimum alveolar concentration) for 1 hr or at 1.4 MAC for 4 hr. Urine and bile were then collected for 11 days following the anesthesia. The concentrations of inorganic fluoride in the urine and bile were measured with a fluoride electrode and an ion meter. The concentration of total fluoride containing organic fluoride also was measured in the same manner after conversion of the organic fluoride to an inorganic form by combustion. The concentration of trifluoroacetic acid (TFA) in the urine was measured by ion chromatography and that in the bile by gas chromatography. Over 80% of all the fluoride was excreted in the urine as organic fluoride in both groups. While the fraction of TFA in the organic fluoride in the bile was about 30% in both groups, that in the urine was 40% in the 0.5 MAC group and 65% in the 1.4 MAC group. Therefore, it was concluded that the organic fluoride compounds, the metabolites of halothane, and in particular TFA, were excreted mostly into the urine. The extent of metabolism of halothane decreased from 7.6% in the 0.5 MAC group to 4.9% in the 1.4 MAC group. The urinary excretion rate of TFA, however, was not affected by the concentration of inspired halothane.     

Urinary excretion of ciclosporin and 17 of its metabolites in renal allograft recipients

Renal elimination of the immunosuppressant ciclosporin is virtually unknown. Therefore, in 17 renal allograft recipients under steady-state conditions we studied the urinary excretion of ciclosporin and 17 of its metabolites in blood and 24-hour urine. Patients with liver dysfunction or treated with drugs potentially influencing the metabolism and elimination of ciclosporin were excluded from the study. Ciclosporin and its metabolites were measured by HPLC. Metabolite but not ciclosporin excretion was strongly correlated with creatinine clearance. Metabolites 18 and 26 (beta, epsilon-cyclic metabolite) were rarely found in blood but were excreted in considerable amounts in urine. Approximately 3% of the administered dose of ciclosporin per day undergoes renal elimination in unchanged form or as metabolites investigated. The data suggest glomerular filtration of ciclosporin metabolites, a difference in the rate of elimination between ciclosporin and the metabolites and some kind of metabolism or active transport mechanism for metabolites in the kidney.     

The analysis of cyclophosphamide and its metabolites.

Cyclophosphamide (CP) has been in clinical use for the treatment of malignant disease for over 40 years. CP is inactive until it undergoes complex metabolic pathways leading to the ultimate alkylating agent, phosphoramide mustard, but also to inactive and toxic metabolites. Sensitive and specific methods are now available for the measurement of CP and its enantiomers, its metabolites and their stereoisomers, in biological matrices. An overview is given of the methods of analysis of CP and its metabolites described in literature since 1993 as well as the current knowledge about its metabolism. Five classes of methods are described: (1) thin-layer chromatography-photographic densitometry, (2) high performance liquid chromatography, (3) gas chromatography and gas chromatography coupled to mass spectrometry, (4) phosphorus-31 nuclear magnetic resonance and (5) enantiomeric separation. In each case, sample clean up and preparation are described. Precision and limits of quantification of the assays are indicated. A table summarizes all the analytical methods for assaying each metabolite.     

Biotransformation of amitriptyline in depressive patients: Urinary excretion of seven metabolites

Summary The urinary excretion of amitriptyline (AMT) and seven of its metabolites was studied by mass spectrometry in 10 depressive in-patients treated to steady-state condition with oral amitriptyline. An average of 68.3% of the dose was recovered in the urine, of which 68.6% was present as conjugates. Hydroxynortriptyline and its conjugate represented 54% of the total recovery. There was marked variation in metabolite pattern between patients. The variations were not due to concomitant medication with benzodiazepines. There was no correlation between the plasma and urine concentrations of AMT and its metabolites, except for amitriptyline conjugates. Two groups of patients could be distinguished — low and high excretors, who displayed alternative routes of metabolism. The disappearance rate of AMT from plasma was determined by the metabolic clearance of AMT to its metabolites. It varied considerably between patients.     

Urinary excretion of p-hydroxylated methamphetamine metabolites in man

p-Hydroxymethamphetamine and p-hydroxyamphetamine in urine samples from methamphetamine addicts were analyzed by high-performance liquid chromatography-electrochemistry (HPLC-EC). The urine samples were hydrolyzed with equal volumes of 12 N HCl at 60 °C for 4 h and were then diluted with water and neutralized with NaOH solution. The neutralized urine was passed through a solid phase extraction column, Bond-Elut^® C₁₈, and after washing, the substances were eluted with acidified acetonitrile. The eluate was evaporated under a stream of nitrogen. The residue was dissolved in 0.1 N PCA and a small volume of the aliquots was injected into the HPLC. This procedure for determination quantitated both free and conjugated forms of the metabolites together. Thereby we could determine concentrations of the metabolites in minute urine samples; i.e., from 2.5 l urine. The free form of the metabolites alone was analyzed by the same procedure except for hydrolysis of the conjugates.Concentrations of methamphetamine, p-hydroxymethamphetamine and p-hydroxyamphetamine in the urine samples of addicts collected at arbitrary times were determined by this procedure or by gas chromatography. It was found that there was no correlation between the concentration of methamphetamine and that of the metabolites. This investigation also revealed that various ratios between the concentrations generally were scattered over a wide range of percentages.     

Urinary excretion of metallothionein-I and its degradation product in rats treated with cadmium, copper, zinc or mercury

The metallothionein-I (MT-I) content of urine following administration of cadmium (Cd), copper (Cu), mercury (Hg) or zinc (Zn) to rats was determined by radioimmunoassay. Urinary excretion of MT-I was increased significantly after injection of each of these metals. Fractionation of urine from Cd-treated rats on Sephadex G-50 showed a single immunoreactive component corresponding to native MT-I, whereas in urine from Cu, Zn or Hg-treated rats 2 immunoreactive components corresponding to MT-I and a possible degradation production were observed. Since a comparable low molecular weight component corresponding to this degradation product was not detected to the same extent on fractionation of plasma from Cu-exposed rat, it seemed to be derived from degradation of MT in the kidney.     

Population pharmacokinetics of cyclophosphamide and its metabolites 4-hydroxycyclophosphamide, 2-dechloroethylcyclophosphamide, and phosphoramide mustard in a high-dose combination with Thiotepa and Carboplatin

The anticancer prodrug cyclophosphamide (CP) is activated by the formation of 4-hydroxycyclophosphamide (4OHCP), which decomposes into phosphoramide mustard (PM). This activation pathway is inhibited by thiotepa. CP is inactivated by formation of 2-dechloroethylcyclophosphamide (2DCECP). The aim of this study was to develop a population pharmacokinetic model describing the complex pharmacokinetics of CP, 4OHCP, 2DCECP, and PM when CP is administered in a high-dose combination with thiotepa and carboplatin. Patients received a combination of CP (1000-1500 mg/m/d), carboplatin (265-400 mg/m/d), and thiotepa (80-120 mg/m/d) administered in short infusions over 4 days. Twenty blood samples were collected per patient per course. Concentrations of CP, 4OHCP, 2DCECP, PM, thiotepa, and tepa were determined in plasma. Using NONMEM, an integrated population pharmacokinetic model was used to describe the pharmacokinetics of CP, 4OHCP, 2DCECP, and PM, including the already described processes of autoinduction of CP and the interaction with thiotepa. Data were available on 35 patients (70 courses). The pharmacokinetics of CP were described with a 2-compartment model, and those of 4OHCP, 2DCECP, and PM with 1-compartment models. Before onset of autoinduction, it was assumed that CP is eliminated through a noninducible pathway accounting for 20% of total CP clearance, whereas 2 inducible pathways resulted in formation of 4OHCP (75%) and 2DCECP (5%). It was assumed that 4OHCP was fully converted to PM. Induction of CP metabolism was mediated by 2 hypothetical amounts of enzyme whose quantities increased in time in the presence of CP (kenz=0.0223 and 0.0198 hours). Induction resulted in an increased formation of 4OHCP (approximately 50%), PM (approximately 50%), and 2DCECP (approximately 35%) during the 4-day course, and concomitant decreased exposure to CP (approximately 50%). The formation of 2DCECP was not inhibited by thiotepa. Apparent volumes of distribution of CP, PM, and 2DCECP could be estimated being 43.7, 55.5, and 18.5 L, respectively. Exposure to metabolites varied up to 9-fold. The complex population pharmacokinetics of CP, 4OHCP, 2DCECP, and PM in combination with thiotepa and carboplatin has been established and may form the basis for further treatment optimization with this combination.     

Urinary excretion of monoamines and metabolites in patients dependent on and withdrawn from barbiturates

Urine collections were made from six barbiturate-dependent subjects immediately prior to, during and after drug withdrawal. Urines were analysed for the monoamines adrenaline, noradrenaline, and dopamine and for the metabolites VMA, HVA and 5-HIAA. Withdrawal did not produce any change in the pattern of excretion and at no time did the excretion of any of these substances differ from normal values.     

Urinary excretion of the 1,4-dihydropyridine calcium antagonist VULM 993 and its metabolites in the rat.

After oral dose of the 1,4-dihydropyridine calcium antagonist 14C-VULM 993 (50 mg/kg) a mean of 44.5% of the administered radioactivity was excreted via urine during the first 72 hours. Using an extractive fractionation procedure, the urinary metabolites were classified on the basis of their polarity and acidic/basic properties. Approx. 40% of total urine metabolites were found to be polar, non-extractable compounds--mostly glucuronide/sulphate conjucates. About one half of all urine metabolites were shown to possess overall acidic nature. G.l.c.-m.s. and t.l.c.-m.s. analyses of urine extracts revealed the presence of only minor amounts of the parent drug toghether with six metabolites identified as products of 1,4-dioxaspiro[4,4]nonane moiety cleavage, hydrolysis of one or both ester side functions also combined with 1,4-dihydropiridine nucleus dehydrogenation. Technique of thin-layer radio-chromatography was used to quantify urinary excretion rates of the parent drug and the established metabolites.