Circadian rhythm of serum sulfate levels in man and acetaminophen pharmacokinetics

CCDB: A database for exploring inter-chemical correlations in metabolomics and exposomics datasets

Inter-chemical correlations in metabolomics and exposomics datasets provide valuable information for studying relationships among chemicals reported for human specimens. With an increase in the number of compounds for these datasets, a network graph analysis and visualization of the correlation structure is difficult to interpret. We have developed the Chemical Correlation Database (CCDB), as a systematic catalogue of inter-chemical correlation in publicly available metabolomics and exposomics studies. The database has been provided via an online interface to create single compound-centric views. We have demonstrated various applications of the database to explore: 1) the chemicals from a chemical class such as Per- and Polyfluoroalkyl Substances (PFAS), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), phthalates and tobacco smoke related metabolites; 2) xenobiotic metabolites such as caffeine and acetaminophen; 3) endogenous metabolites (acyl-carnitines); and 4) unannotated peaks for PFAS. The database has a rich collection of 35 human studies, including the National Health and Nutrition Examination Survey (NHANES) and high-quality untargeted metabolomics datasets. CCDB is supported by a simple, interactive and user-friendly web-interface to retrieve and visualize the inter-chemical correlation data. The CCDB has the potential to be a key computational resource in metabolomics and exposomics facilitating the expansion of our understanding about biological and chemical relationships among metabolites and chemical exposures in the human body. The database is available at www.ccdb.idsl.me site.

Chronopharmacology in Therapeutic Drug Monitoring-Dependencies between the Rhythmics of Pharmacokinetic Processes and Drug Concentration in Blood

The objective of the optimization of pharmacotherapy compliant with the basic rules of clinical pharmacology is its maximum individualization, ensuring paramount effectiveness and security of the patient's therapy. Thus, multiple factors that are decisive in terms of uniqueness of treatment of the given patient must be taken into consideration, including, but not limited to, the patient's age, sex, concomitant diseases, special physiological conditions (e.g., pregnancy, lactation, extreme age groups), polypharmacotherapy and polypragmasia (particularly related to increased risk of drug interactions), and patient's phenotypic response to the administered drug with possible genotyping. Conducting therapy while monitoring the concentration of certain drugs in blood (Therapeutic Drug Monitoring; TDM procedure) is also one of the factors enabling treatment individualization. Furthermore, another material, and yet still a marginalized pharmacotherapeutic factor, is chronopharmacology, which indirectly determines the values of drug concentrations evaluated in the TDM procedure. This paper is a brief overview of chronopharmacology, especially chronopharmacokinetics, and its connection with the clinical interpretation of the meaning of the drug concentrations determined in the TDM procedure.

A comparative review of use of sulphate and phosphate salts for colonoscopy preparations and their potential for nephrotoxicity

Background and study aims  Colonoscopy is a widely used diagnostic procedure which requires prior cleansing of the bowel. Many different bowel cleansing preparations have been developed, all of which have specific advantages and disadvantages. This review compares two low-volume high-osmolarity bowel cleansing preparations, oral phosphate salts and oral sulphate salts, with a particular focus on risk of nephrotoxicity. Patients and methods  An electronic search of the Medline database was performed using the search terms "(phosphates OR sulfates) AND cathartics [MeSH Term] AND kidney" restricted to humans with a cut-off date of December 31, 2016. Results  Introduction of oral phosphate salts offered the advantage of low intake volume and low risk of bowel irritation compared to previous options. However, phosphate salts have been associated with renal toxicity (acute phosphate nephropathy [APN]), thought to arise due to perturbations of calcium and phosphate homeostasis as a consequence of increases in serum phosphate. This results in high concentrations of calcium phosphate in the distal tubule and collecting ducts of the kidney, where it may precipitate. Although APN is rare, it may lead to permanent kidney damage. For this reason, phosphate salts are contraindicated in vulnerable patient groups. As an alternative to phosphate salts, oral sulphate salts have recently been introduced. Because sulphate absorption from the intestinal tract is saturable, serum sulphate concentrations increase only minimally after ingestion. Furthermore, excretion of sulphate in the kidney is not accompanied by calcium excretion and urine calcium levels are unchanged. For these theoretical reasons, use of sulphate salts as bowel cleansing solutions is not expected to lead to calcium precipitation in the nephron. Conclusions  Oral phosphate salts are no longer recommended for routine use as bowel cleansing preparations as they carry significant risk of kidney damage and a safer alternative is available in the form of oral sulphate solutions. To date, use of sulphate salts has not been associated with elevations in serum creatinine or other markers of renal impairment, nor with clinical manifestations of kidney injury. Nonetheless, experience with sulphate salts in everyday practice is limited and physicians should be vigilant in detecting potential safety issues.

Chronopharmacokinetics of drugs in toxicological aspects: A short review for pharmacy practitioners

A rough 24-hour cycle driven endogenously in biochemical, physiological or behavioral processes is called circadian rhythm. Chronobiology is the study of biological temporal rhythms. For decades, we know that the biological rhythm and the drug metabolism are also affected from daylight and chronopharmacology became recognized by scientists in the early 1970s. Its lateral branch chronocopharmacokinetics is the study of rhythmic, predictable-in-time differences in the pharmacokinetics of drugs. Chronopharmacokinetic studies are performed at every step of the biotransformation i.e., absorption, distribution, metabolism and excretion. Feeding schedules, sex and phenotype must be taken into consideration while applying pharmacotherapy to increase the efficiency and to decrease side effects. The impact of drugs on circadian rhythm should be not neglected. On the other hand, new special drug delivery systems can be used to synchronize drug concentrations according to circadian rhythms. “Chronopharmaceuticals” can identify the proper dosing time and this amelioration will lead to improved progress and diffusion of pharmacotherapy. Chronopharmaceuticals coupled with nanotechnology could be the future of drug delivery systems, and lead to safer and more efficient disease therapy in the future. In this review, we will discuss the pharmacokinetic effects of circadian rhythm and its toxicological outcomes. Besides, we will try to give some practical points for clinical pharmacist/pharmacy practitioners, concerning chronopharmacokinetics.

Nutritional essentiality of sulfur in health and disease

Sulfur is the seventh most abundant element measurable in the human body and is supplied mainly by the intake of methionine (Met), an indispensable amino acid found in plant and animal proteins. Met controls the initiation of protein synthesis, governs major metabolic and catalytic activities, and may undergo reversible redox processes safeguarding protein integrity. Withdrawal of Met from customary diets causes the greatest downsizing of lean body mass following either unachieved replenishment (malnutrition) or excessive losses (inflammation). These physiopathologically unrelated morbidities nevertheless stimulate comparable remethylation reactions from homocysteine, indicating that Met homeostasis benefits from high metabolic priority. Inhibition of cystathionine-β-synthase activity causes the upstream sequestration of homocysteine and the downstream drop in cysteine and glutathione. Consequently, the enzymatic production of hydrogen sulfide and the nonenzymatic reduction of elemental sulfur to hydrogen sulfide are impaired. Sulfur operates as cofactor of several enzymes critically involved in the regulation of oxidative processes. A combination of malnutrition and nutritional deprivation of sulfur maximizes the risk of cardiovascular disorders and stroke, constituting a novel clinical entity that threatens plant-eating population groups.

Higher calcium urinary loss induced by a calcium sulphate-rich mineral water intake than by milk in young women Comments by Arnaud

I did not intend to revisit the discussion of the publication of Brandolini et al.1 on Ca urinary excretion attributed to the sulfate content of water but in their answers2 to my comments3, they said that ‘I accept their experimental results’ and that ‘I do not contest the difference in calciuria between milk and sulfate-rich water’. I never wrote that I agree with their results and even more with their conclusions but questioned how is it possible to evaluate a 20 mg difference in daily Ca urinary excretion from a study with subjects under uncontrolled dietary intakes, unbalanced experimental study design and without analytical results on acid–base balance and sulfate to support their acidogenic hypothesis of sulfate. I did not find any convincing explanations in their answers but I want to raise several points of disagreement, which are either repeated or new.

Disposition of Acetaminophen at 4, 6, and 8 g/day for 3 Days in Healthy Young Adults

The objective of this study was to determine the disposition and tolerability of 1, 1.5, and 2 g acetaminophen every 6 h for 3 days. Group I healthy adults received acetaminophen (4 then 6 g/day) or placebo; Group II received acetaminophen (4 then 8 g/day) or placebo. Acetaminophen and metabolites were measured in plasma and urine. Hepatic aminotransferases were measured daily. At steady state, acetaminophen concentrations were surprisingly lower than predicted from single-dose data, although sulfate formation clearance (fCL) was lower as expected, indicating cofactor depletion with possible sulfotransferase saturation. In contrast, glucuronide fCL was unexpectedly higher, strongly suggesting glucuronosyltransferase induction. This is the first evidence that acetaminophen induces its own glucuronidation. No dose-dependent differences were detected in fCL of thiol metabolites formed via cytochrome P4502E1. Hepatic aminotransferases stayed within reference ranges, and the incidence and frequency of adverse events were similar for acetaminophen and placebo. Although dose-dependence of acetaminophen disposition was reported previously, this study shows a novel finding of time-dependent disposition during repeated dosing. Unexpected increases in glucuronide fCL more than offset decreases in sulfate fCL, thus increasing acetaminophen clearance overall. Thiol metabolite fCL remained constant up to 8 g/day. These findings have important implications in short-term (3 day) tolerability of supratherapeutic acetaminophen doses in healthy adults.

Sulphate and osteoarthritis: decrease of serum sulphate levels by an additional 3-h fast and a 3-h glucose tolerance test after an overnight fast

BACKGROUND

Low sulphate levels in blood may contribute to osteoarthritis by decreasing cartilage chondroitin sulphation.

OBJECTIVE

To measure serum levels of sulphate during 3 h of fasting or glucose ingestion after overnight fasts to determine how much sulphate lowering may occur during this period.

METHODS

Sera from 14 patients with osteoarthritis who fasted overnight were obtained every 15-30 min during 3 h of continued fasting and during 3 h after ingestion of 75 g of glucose. Sulphate was assayed by high-performance liquid chromatography with a Metrohm-Peak 761 Compact IC and simultaneously assayed for glucose by high-performance liquid chromatography with a Metrohm-Peak 817 Bioscan.

RESULTS

Continuation of overnight fasting for 3 h resulted in a near-linear 3-h decrease in levels for all 14 patients ranging from 3% to 20% with a mean drop of 9.3%, whereas the 3-h decrease after glucose ingestion ranged from 10% to 33% with a mean drop of 18.9%.

CONCLUSION

A 3-h continuation of fasting caused a marked reduction in serum sulphate levels, whereas ingestion of 75 g of glucose in the absence of protein resulted in doubling the reduction. This suggests that fasting and ingestion of protein-free calories may produce periods of chondroitin undersulphation that could affect osteoarthritis.

The nutritional relationship linking sulfur to nitrogen in living organisms

Nitrogen (N) and sulfur (S) coexist in the biosphere as free elements or in the form of simple inorganic NO3- and SO4(2-) oxyanions, which must be reduced before undergoing anabolic processes leading to the production of methionine (Met) and other S-containing molecules. Both N and S pathways are tightly regulated in plant tissues so as to maintain S:N ratios ranging from 1:20 to 1:35. As a result, plant products do not adequately fulfill human tissue requirements, whose mean S:N ratios amount to 1:14.5. The evolutionary patterns of total body N (TBN) and of total body S (TBS) offer from birth to death sex- and age-related specificities well identified by the serial measurement of plasma transthyretin (TTR). Met is regarded as the most limiting of all indispensable amino acids (IAAs) because of its participation in a myriad of molecular, structural, and metabolic activities of survival importance. Met homeostasis is regulated by subtle competitive interactions between transsulfuration and remethylation pathways of homocysteine (Hcy) and by the actual level of TBN reserves working as a direct sensor of cystathionine-beta-synthase activity. Under steady-state conditions, the dietary intake of SO4(2-) is essentially equal to total sulfaturia. The recommended dietary allowances for both S-containing AAs allotted to replace the minimal obligatory losses resulting from endogenous catabolism is largely covered by Western customary diets. By contrast, strict vegans and low-income populations living in plant-eating countries incur the risk of chronic N and Met dietary deficiencies causing undesirable hyperhomocysteinemia best explained by the downsizing of their TBN resources and documented by declining TTR plasma values.

Human sulfate kinetics

Electrospray tandem mass spectrometry was used to determine steady-state serum and urinary inorganic sulfate and sulfate ester kinetic profiles of nine normal men after intravenous injection of the stable isotope sodium [34S]sulfate. Sulfate ester appearance was traced by eliminating inorganic sulfate from samples, followed by hydrolysis of sulfate esters to inorganic sulfate for analysis. Whole body inorganic sulfate turnover in steady state was calculated using standard tracer techniques. Rate of appearance and disappearance of inorganic sulfate was 841 ± 49 μmol/h. Average urinary inorganic sulfate excretion was 609 ± 41 μmol/h, and the whole body sulfation rate (total rate of disappearance minus rate of urinary excretion) was 232 ± 36 μmol/h. Tracer-labeled sulfate esters appeared in serum and urine within 1 h of tracer injection. The kinetics of inorganic sulfate and sulfate esters were linked by means of a compartmental model. The appearance and excretion of sulfate esters accounted for ∼ 50% of the total sulfation rate. These results indicate that human whole body sulfation accounts for ∼ 27% of inorganic sulfate turnover and that extracellular inorganic sulfate is an important pool for intracellular sulfation. A substantial fraction of newly synthesized sulfate esters promptly enters the extracellular space for excretion in the urine.

Fasting serum sulfate levels before and after development of osteoarthritis in participants of the veterans administration normative aging longitudinal study do not differ from levels in participants in whom osteoarthritis did not develop

OBJECTIVE

To determine whether the development of osteoarthritis (OA) in men over a 33-year period is related to lower sulfate levels in stored serum collected during that time interval.

METHODS

Stored serum samples from participants in the Veterans Administration Normative Aging Study were assayed for sulfate by ion-exchange chromatography. Samples had been obtained every 3-5 years during part or all of a 33-year portion of the study. Sulfate levels were determined in serum from all participants who underwent knee replacement surgery and had evidence of radiographic hand OA, from some of the participants who had evidence of radiographic hand OA but had not undergone knee replacement surgery, from all participants who underwent knee replacement surgery but had no evidence of radiographic hand OA, and from age-matched participants who had no evidence of OA by history, physical examination, or hand radiography.

RESULTS

Serum sulfate levels in participants, with or without radiographic hand OA and/or knee replacements, who were ages 34-72 years at the first examination, ranged from 0.21 mM to 0.51 mM over the course of a maximum of 33 years. Both the overall mean and median sulfate levels rose from 0.32 mM at age 40-50 years to 0.38 mM at age 70-80 years, and the overall mean and median for all ages was 0.36 mM. There were no significant differences in sulfate levels between subjects in any of the 4 groups.

CONCLUSION

There was no evidence of a relationship between these serum sulfate levels and the development of OA. However, all samples were collected after overnight fasting, and no participant was younger than age 34 years at the initiation of the study. It remains to be determined whether differences in the time of ingestion of daily dietary protein providing sulfate are related to the development of OA, or whether sulfate levels measured at an earlier age could be a factor.

Paracetamol and metabolite pharmacokinetics in infants

BACKGROUND

Data concerning metabolism of paracetamol in infants are scant. Previous studies have examined urinary metabolite recovery rates after a single dose of paracetamol in either neonates (<6 weeks) or children (3-9 years). There are no studies investigating infants.

METHODS

Infants ( n=47) undergoing major craniofacial surgery were given paracetamol 19-45 mg/kg 6-, 8-, or 12-hourly as either elixir or suppository formulation for postoperative analgesia, after a loading dose of 33-59 mg/kg rectally during the operation. Serum was assayed for paracetamol concentration in 40 of these infants at 5, 8, 11, 14, 17 and 20 h postoperatively. Urine samples were collected every 3 h for 24 h in 15 of these infants. The clearances of paracetamol to glucuronide and sulphate metabolites as well as the urinary clearance of unmetabolised paracetamol were estimated using non-linear, mixed-effects models.

RESULTS

Mean (+/-SD) age and weight of the patients were 11.8+/-2.5 months and 9.1+/-1.9 kg. Clearances of paracetamol to paracetamol-glucuronide (%CV) and to paracetamol-sulphate were 6.6 (11.5) l/h and 7.5 (11.5) l/h respectively, standardised to a 70-kg person using allometric "1/4 power" models. Glucuronide formation clearance, but not sulphate formation, was related to age and increased with age from a predicted value in a neonate of 2.73 l/h/70 kg to a mature value of 6.6 l/h/70 kg with a maturation half-life of 8.09 months. Urine clearance of paracetamol-glucuronide, paracetamol-sulphate and unchanged paracetamol (%CV) were, respectively, 2.65, 3.03 and 0.55 (28) l/h/70 kg. The urine clearance of unchanged paracetamol and metabolites was related to urine volume flow rate. Clearance attributable to pathways other than these measured in urine was not identifiable. The glucuronide/sulphate formation clearance ratio was 0.69 at 12 months of age. Sulphate metabolism contributed 50% towards paracetamol clearance.

CONCLUSION

Glucuronide formation clearance increases with age in the infant age range but sulphate formation does not. Renal clearance of paracetamol and its metabolites increases with urine flow rate. This and other studies show that paracetamol metabolism to glucuronide appears to be similar in infants and children, but in adults is increased in comparison with children. Oxidative pathways were undetectable in this infant study and may explain, in part, the reduced incidence of hepatotoxicity in infants.

Circadian rhythms of paracetamol metabolism in healthy subjects; a preliminary report

Paracetamol was used as a "probe" drug to study the circadian rhythms of metabolite ratios in man. Paracetamol was orally administered to six volunteers at different times of day, 0-8 h and 8-24 h urine samples being measured for sulphate and glucuronide formation. Results showed a wide interindividual variation in paracetamol metabolite excretion among the six subjects. However, when a 500 mg dose was administered, free paracetamol excretion was minimal when the dose was given at 12.00 h and maximal when given at 20.00 h for the 0-8 h collection period. Sulphate excretion rose slightly at night and decreased gradually during the day. Glucuronide excretion was greatest with drug administration at 16.00 h and least if paracetamol was ingested at 08.00 h. The 8-24 h profiles were roughly similar. At a higher dose (1500 mg), free paracetamol excretion showed a minimum from dosing at 20.00 h and a maximum from dosing at 24.00 h in both 0-8 h and 8-24 h collections, while the sulphate conjugate peaked for doses at 20.00 h and 8.00 h with collections at 0-8 h and 8-24 h respectively. The glucuronide conjugate was maximal for paracetamol administration at 16.00 h for both 0-8 h and 8-24 h collections. There appears to be a 12 hour phase variation in excretion; this may result from circadian rhythms in absorption and enzyme activities. These parameters may also affect metabolism at higher dose levels, so that the hepatotoxicity of paracetamol could vary with the time of dose.

Use of sulfate production as a measure of short-term sulfur amino acid catabolism in humans

There is no fully satisfactory method for measuring amino acid catabolism in the nonsteady state that follows normal protein consumption. Because sulfate is the major product of sulfur amino acid catabolism, we tested whether its production can be accurately depicted using simple tracer or nontracer approaches under basal conditions and after the intravenous administration of a known amount of sulfate. In the basal postabsorptive state, serum sulfate concentration and urinary sulfate excretion remained constant for many hours, but the apparent steady-state serum sulfate rate of appearance achieved with primed continuous oral administration of sodium [(34)S]sulfate was 20% higher than urinary sulfate excretion. By contrast, after magnesium sulfate infusion, the increase in sulfate production above basal accounted for 95% over 6 h and 98% over 9 h of the administered dose when measured simply as urinary inorganic sulfate excretion corrected for changes in its extracellular fluid content. Using the latter method, we measured sulfate production after oral methionine and intravenous infusion of methionine in a mixture of other essential amino acids. Sulfate production above basal accounted for 59% over 6 h and 75% over 9 h of the oral methionine dose. Similar results were obtained with the mixed amino acid infusion, but interpretation of the latter experiment was limited by the mild protein sparing (and, hence, reduced endogenous sulfate production) induced by the amino acid infusion. We conclude that a simple nontracer method can provide an accurate measure of sulfate production and, hence, sulfur amino acid catabolism over collection periods as short as 6 h after a test meal. A significant portion of the sulfur derived from methionine appears to be retained in nonprotein compounds immediately after its ingestion.

Molecular aspects of renal tubular handling and regulation of inorganic sulfate

The renal proximal tubular reabsorption of sulfate plays an important role in the maintenance of sulfate homeostasis. Two different renal sulfate transport systems have been identified and characterized at the molecular level in the past few years: NaSi-1 and Sat-1. NaSi-1 belongs to a Na(+)-coupled transporter family comprising the Na(+)-dicarboxylate transporters and the recently characterized SUT1 sulfate transporter. NaSi-1 is a Na(+)-sulfate cotransporter located exclusively in the brush border membrane of renal proximal tubular and ileal cells. Recently, NaSi-1 was shown to be regulated at the protein and mRNA level by a number of factors, such as vitamin D, dietary sulfate, glucocorticoids and thyroid hormones, which are known to modulate sulfate reabsorption in vivo. The second member of renal sulfate transporters, denoted Sat-1, belongs to a family of Na+-independent sulfate transporter family comprising the DTDST, DRA and PDS genes. Sat-1 is a sulfate/bicarbonate-oxalate exchanger located at the basolateral membrane of proximal tubular epithelial cells and canalicular surface of hepatic cells. Contrary to NaSi-1, no physiological factor has been found to date to regulate Sat-1 gene expression. Both NaSi-1 and Sat-1 transporter activities are implicated in pathophysiological states such as heavy metal intoxication and chronic renal failure. This review focuses on recent developments in the molecular characterization of NaSi-1 and Sat-1 and the mechanisms involved in their regulation.

The clinical chemistry of inorganic sulfate

Although inorganic sulfate is an essential and ubiquitous anion in human biology, it is infrequently assayed in clinical chemistry today. Serum sulfate is difficult to measure accurately without resorting to physicochemical methods, such as ion chromatography, although many other techniques have been described. It is strongly influenced by a variety of physiological factors, including age, diet, pregnancy, and drug ingestion. Urinary excretion is the principal mechanism of disposal for the excess sulfate produced by sulfur amino acid oxidation, and the kidney is the primary site of regulation. In renal failure, sulfoesters accumulate and hypersulfatemia contributes directly to the unmeasured anion gap characteristic of the condition. In contrast, sulfate in urine is readily assayed by a number of means, particularly nephelometry after precipitation as a barium salt. Sulfate is most commonly assayed today as part of the clinical workup for nephrolithiasis, because sulfate is a major contributor to the ionic strength of urine and alters the equilibrium constants governing saturation and precipitation of calcium salts. Total sulfate deficiency has hitherto not been described, although genetic defects in sulfate transporters have been associated recently with congenital osteochondrodystrophies that may be lethal. New insights into sulfate transport and its hormonal regulation may lead to new clinical applications of sulfate analysis in the future.

Molecular mechanisms of renal sulfate regulation

Inorganic sulfate is an important physiological anion that is a required cofactor for sulfate conjugation reactions of both endogenous and exogenous compounds. It is necessary for the detoxification of xenobiotics and endogenous compounds (catecholamines, steroids, bile acids), for the synthesis of structural components of membranes and tissues (sulfated glycosaminoglycans), and for the biologic activity of endogenous compounds (heparin and cholecystokinin). Inorganic sulfate homeostasis is largely maintained by reabsorption in the renal proximal tubule. Sodium-dependent sulfate cotransport in the brush border membrane is of primary importance in the regulation of plasma inorganic sulfate concentrations. Altered renal reabsorption of sulfate has been observed under different physiological (age, pregnancy, low dietary intake), pathological (hypothyroidism, trace metal excess), and pharmacological conditions (treatment with nonsteroidal antiinflammatory agents). The recent identification of the sulfate transporter genes has allowed the investigation of the molecular mechanisms of altered sulfate transport. Although the regulation of sulfate homeostasis is not fully understood, recent investigations have explored the cellular mechanisms of some of these alterations. In this review, the physiological importance of inorganic sulfate, the availability of this anion, and the regulation of sulfate homeostasis are discussed.

Quantitation of sulfate and thiosulfate in clinical samples by ion chromatography

For assay of serum sulfate, quantitation by ion conductimetry after separation by anion-exchange chromatography is the method of choice. In comparison to classical barium precipitation methods, chromatographic methods demonstrate increased precision, specificity and sensitivity, and they may be superior to spectrophotometric methods that rely on organic cation precipitation of sulfate. The increased sensitivity and specificity, as well as the inherent capacity of chromatographic methods for simultaneous determination of other anions, has led to its increasing use in the determination of excreted sulfate in clinical profiles of urinary anion composition. Ion chromatography can also be used to quantitate free sulfate in other clinical samples, including cerebrospinal fluid, sweat, saliva, breast milk and human tissues. Finally, ion chromatography shows promise as a more precise and sensitive method for measurement of total acid-labile sulfoesters and thiosulfate.

Human metabolism of paracetamol (acetaminophen) at different dose levels

Urine (0-24 h) was collected from five subjects on separate occasions following the ingestion of paracetamol at five different dose levels (500, 750, 1000, 1250, 1500 mg) which spanned the normal therapeutic range. The major urinary metabolites were sulphuric and glucuronic acid conjugates which together accounted for around 50% of the administered dose. Unchanged paracetamol excretion was low (5-20%). This situation was similar over the entire dose range. These findings are discussed in relation to previous single dose studies reported in the literature.

Simple method for the determination of inorganic sulfate in human serum and urine using single-column ion chromatography

A single-column ion chromatographic assay with conductivity detection was developed to determine inorganic sulfate concentrations in human plasma and urine samples. Plasma samples were ultrafiltered to remove proteins. Plasma ultrafiltrate and urine samples were diluted prior to injection onto the anion-exchange column. The described method is simple, fast, sensitive and reproducible and was used to study the effect of subchronic administration of acetaminophen on the plasma concentrations and urinary excretion of inorganic sulfate in healthy volunteers.