The effect of acetaminophen administration on its disposition and body stores of sulphate

Maturation of Paracetamol Elimination Routes in Preterm Neonates Born Below 32 Weeks of Gestation

PURPOSE

Despite being off-label, intravenous paracetamol (PCM) is increasingly used to control mild-to-moderate pain in preterm neonates. Here we aim to quantify the maturation of paracetamol elimination pathways in preterm neonates born below 32 weeks of gestation.

METHODS

Datasets after single dose (rich data) or multiple doses (sparse data) of intravenous PCM dose (median (range)) 9 (3-25) mg/kg were pooled, containing 534 plasma and 44 urine samples of PCM and metabolites (PCM-glucuronide, PCM-sulfate, PCM-cysteine, and PCM-mercapturate) from 143 preterm neonates (gestational age 27.7 (24.0-31.9) weeks, birthweight 985 (462-1,925) g, postnatal age (PNA) 5 (0-30) days, current weight 1,012 (462-1,959) g. Population pharmacokinetic analysis was performed using NONMEM® 7.4.

RESULTS

For a typical preterm neonate (birthweight 985 g; PNA 5 days), PCM clearance was 0.137 L/h, with glucuronidation, sulfation, oxidation and unchanged renal clearance accounting for 5.3%, 73.7%, 16.3% and 4.6%, respectively. Maturational changes in total PCM clearance and its elimination pathways were best described by birthweight and PNA. Between 500-1,500 g birthweight, total PCM clearance increases by 169%, with glucuronidation, sulfation and oxidation clearance increasing by 347%, 164% and 164%. From 1-30 days PNA for 985 g birthweight neonate, total PCM clearance increases by 167%, with clearance via glucuronidation and oxidation increasing by 551%, and sulfation by 69%.

CONCLUSION

Birthweight and PNA are the most important predictors for maturational changes in paracetamol clearance and its glucuronidation, sulfation and oxidation. As a result, dosing based on bodyweight alone will not lead to consistent paracetamol concentrations among preterm neonates.

Consensus Statement on the Use of Oral Contraceptive Pills in Polycystic Ovarian Syndrome Women in India

OBJECTIVE

To provide consensus recommendations for health-care providers on the use of oral contraceptive pills (OCPs) in polycystic ovarian syndrome (PCOS) women in India.

PARTICIPANTS

Extensive deliberations, discussions, and brainstorming were done with different fraternities (specialists) being involved. These included endocrinologists, gynecologists, reproductive endocrinologists, dermatologists, public health experts, researchers, and a project manager with a team to develop the guideline.

EVIDENCE

Published literature was retrieved through searches of Medline and The Cochrane Database from January 2003 to December 2017 using appropriate-controlled vocabulary (e.g., oral contraceptive pills, polycystic ovarian syndrome, long term outcomes, infertility). Clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies' publications and data were also reviewed to suggest the recommendations.

PROCESS

The working group for guideline committee included members from the PCOS Society (India), Indian Society for Assisted Reproduction, The Mumbai Obstetric and Gynecological Society, The Endocrine Society of India, Indian Association of Dermatologists, Venereologists and Leprologists, Cosmetic Dermatology Society (India), Academicians from Medical Colleges, National Institute for Research in Reproductive Health, and a Research Associate. The core team included five reproductive endocrinologists, five gynecologists, five dermatologists, three endocrinologists, two public health experts and one research associate.

CONCLUSIONS

This consensus statement provides the guidance/recommendations for Indian practitioners regarding the use of OCP in women with PCOS. PCOS is one of the common endocrinopathies encountered in gynecological/endocrine practice. The spectrum of this disorder may range from prepubertal girls with premature pubarche, young girls with hirsutism, acne and anovulatory cycles, married women with infertility, and elderly women. Although obesity is a common feature for most PCOS patients, 'lean PCOS' also exists. For several years, OCPs have played an important role in the symptom management of PCOS women. This is due to the fact that OCPs decrease the luteinizing hormone, reduce androgen production, and increase sex hormone-binding globulin, which binds androgens. Several new formulations of OCPs have been developed to decrease the side effects. This includes use of less androgenic progestins and lower doses of ethinyl estradiol. These consensus recommendations help the health provider to choose the right type of OCPs, which will alleviate the symptoms with least side effects. It also gives insight into the indications, contraindications, and concerns regarding its short, intermediate and long-term use.

Can paracetamol (acetaminophen) be administered to patients with liver impairment?

Although 60 years have passed since it became widely available on the therapeutic market, paracetamol dosage in patients with liver disease remains a controversial subject. Fulminant hepatic failure has been a well documented consequence of paracetamol overdose since its introduction, while short and long term use have both been associated with elevation of liver transaminases, a surrogate marker for acute liver injury. From these reports it has been assumed that paracetamol use should be restricted or the dosage reduced in patients with chronic liver disease. We review the factors that have been purported to increase risk of hepatocellular injury from paracetamol and the pharmacokinetic alterations in different pathologies of chronic liver disease which may affect this risk. We postulate that inadvertent under-dosing may result in concentrations too low to enable efficacy. Specific research to improve the evidence base for prescribing paracetamol in patients with different aetiologies of chronic liver disease is needed.

Variability in UDP-glucuronosyltransferase genes and morphine metabolism: observations from a cross-sectional multicenter study in advanced cancer patients with pain

OBJECTIVE

The objective of the present study was to determine whether genetic variability in UDP-glucuronosyltransferase (UGT) genes, together with clinical factors, contribute to variability in morphine glucuronide (M6G and M3G) to morphine serum concentration ratios in patients with advanced cancer receiving chronic morphine therapy.

MATERIALS AND METHODS

A total of 41 polymorphisms and predicted haplotypes in the UGT2B7, UGT1A1, and UGT1A8 genes were analyzed in 759 patients who were recruited from the European Pharmacogenetic Opioid Study and received chronic morphine therapy by the oral route (n=635) or parenterally (n=124). The administration groups were analyzed separately by multiple linear regression analyses.

RESULTS

Two haplotypes in UGT1A1/UGT1A8 were weak predictors of reduced M6G/morphine and M3G/morphine serum ratios after oral administration (false discovery rate-corrected P-values<0.1). No effect of genotype was seen in the parenteral group. Of the clinical variables (age, sex, BMI, renal function, Karnofsky performance status, and presence of liver metastases), renal function was the major contributor to variation in serum concentration ratios. Concomitant administration of paracetamol predicted significantly higher morphine metabolic ratios after oral administration of morphine (false discovery rate-corrected P-values<2.1E-12). The regression models explained about 35% of the total variability in the data.

CONCLUSION

Genetic variation in the UGT genes together with clinical factors influence morphine metabolic ratios in patients with advanced cancer disease and who are scheduled with oral morphine. This information may be included in future research that develop and test new classification systems for opioid treatment in patients with advanced cancer.

Fulminant hepatitis after 10 days of acetaminophen treatment at recommended dosage in an infant

Acetaminophen is considered a safe drug for children, although hepatotoxicity may develop after overdosing. Reports of liver failure after repeated therapeutic doses of the drug have been rare. Here we describe the case of an infant who developed acute liver failure after administration of acetaminophen for 10 days at a total dose of 720 mg/day (72 mg/kg per day). The patient had high levels of aspartate aminotransferase (11 735 U/L) and alanine aminotransferase (6611 U/L) accompanied by encephalopathy and an increased ammonium level (266 μg/dL). Intravenous N-acetylcysteine therapy resulted in rapid improvement of the child's clinical condition and laboratory test results. Health care providers should be aware that multiple doses of acetaminophen in infants may lead to acute hepatic failure. N-acetylcysteine therapy should be initiated in cases of drug-induced acute liver failure.

Acetaminophen safety and hepatotoxicity--where do we go from here?

Acetaminophen has been widely used for > 50 years in the treatment of pain and fever and provides for the safe and effective relief of these symptoms. In a small minority of patients, however, acetaminophen is responsible for life-threatening liver injury and accounts for up to 50% of all adult cases of acute liver failure in the US. Although approximately two-thirds of adult overdoses are associated with suicide attempts, many are inadvertent, often due to the use of multiple acetaminophen formulations over many days. Additionally, some individuals appear to experience acetaminophen toxicity at 'therapeutic' doses of < 4 g/day, for reasons unknown. In pediatric populations, the overwhelming majority of acetaminophen overdoses are due to unintentional overdoses, except for the predominance of suicidal ingestions in the teenage population. This article seeks to review the mechanism and metabolism of acetaminophen and the features of toxicity in adults, pediatric and special populations. Additionally, expert opinion is presented herein to aid in reducing the frequency and severity of liver injury from acetaminophen.

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.

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.

Intra- and interindividual variability of glucuronidation of paracetamol during repeated administration of propacetamol in neonates

BACKGROUND

Major changes in drug clearance and metabolism are observed during infancy, in part based on ontogenic regulation of various metabolic pathways. Since paracetamol provides a good substrate to study UGT (1A6) activity, urinary metabolites of propacetamol were determined in neonates in whom propacetamol was repeatedly administered.

METHODS

Paracetamol glucuronide (APAP-G), paracetamol sulphate (APAP-S) and free paracetamol were determined in urine samples of neonates during repeated administration of propacetamol. Spearman rank and linear multiple regression (MedCalc, Mariakerke, Belgium) were used to study the effect of postnatal age, of postconceptional age and of repeated administration on the relative contribution of APAP-G to overall urine paracetamol (APAP-G+APAP-S+free paracetamol) elimination (G/T ratio).

RESULTS

147 samples were collected in 23 neonates. Molar median G/T ratio was 14% (range 1-53). Besides increasing G/T ratio with increasing postnatal (p<0.0001) and postconceptional age (p<0.01), repeated administration (p<0.01) also correlated with an increasing G/T ratio, and repeated administration remained significant (p<0.01) after correction of postnatal and postconceptional age in a multiple regression model.

CONCLUSION

Major variability in the ontogeny of UGT activity to overall elimination of paracetamol was documented in neonates. Besides postnatal and postconceptional age, a significant effect of repeated administration on UGT activity was documented.

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.

The effects of acetaminophen on pharmacokinetics and pharmacodynamics of warfarin

The oral anticoagulant warfarin is clinically administered as a racemic mixture of two enantiomers, (R) and (S). Many relevant drug interactions with warfarin have been attributed to the specific metabolic inhibition of the elimination of the more pharmacologically active (S)-enantiomer. To investigate reports that acetaminophen can potentiate the anticoagulant effect of warfarin, 20 healthy male volunteers were each given single oral 20 mg doses of racemic warfarin on three separate occasions: (1) alone, (2) after 1 day of acetaminophen (4 g/d), and (3) after 2 weeks of acetaminophen (4 g/d). The urinary excretion pattern of acetaminophen and its metabolites was not significantly altered over its course of administration. The (R)- and (S)-enantiomers of warfarin exhibited significantly different pharmacokinetic properties. However, acetaminophen did not alter the disposition of either (R)- or (S)-warfarin. All subjects exhibited a pharmacodynamic response to racemic warfarin. The response was not significantly altered in the presence of acute or chronic acetaminophen dosing, as assessed by prothrombin time and factor VII concentrations.

Therapeutic misadventures with acetaminophen: hepatoxicity after multiple doses in children

We compiled reports of acetaminophen hepatotoxicity after multiple overdoses from published cases, cases reported to the Food and Drug Administration, and cases from Children's Hospital Medical Center, Cincinnati, Ohio. Forty-seven children (age range, 5 weeks to 10 years) received 60 to 420 mg/kg/day for 1 to 42 days; 52% had received adult preparations of acetaminophen. The mean peak serum aspartate aminotransferase level was 10,225 IU/L (n = 45), and the mean serum alanine aminotransferase level was 7355 IU/L (n = 31), which were significantly higher (both p < 0.001) than the mean serum aspartate aminotransferase level of 3500 IU/L and alanine aminotransferase level of 3098 IU/L found in children (n = 12) with non-acetaminophen-associated hepatic failure. Serum acetaminophen levels for which an estimate of time from last dose could be calculated were available for 30 patients, of which 22 levels were greater than the toxic range described for acute ingestion. Twenty-four of 43 patients (55%) died, with an additional three surviving after orthotopic liver transplantation. Parents should be advised about the potential hepatotoxicity of acetaminophen when given to ill children in doses exceeding weight-based recommendations.

Paracetamol (acetaminophen) poisoning

Paracetamol poisoning caused by intentional overdose remains a common cause of morbidity. In this article the mechanism of toxicity and the clinical effects and treatment of poisoning, including specific antidotal therapy, are reviewed. Areas for further research directed at reducing morbidity and mortality from paracetamol poisoning are considered.

The disposition of paracetamol and its conjugates during multiple dosing in patients with end-stage renal failure maintained on haemodialysis

The disposition of oral paracetamol (1.0 g 3 times daily for 10 days) was studied in 6 patients with end-stage renal failure (creatinine clearance < 5 ml x min-1) maintained on haemodialysis 2 or 3 times per week. Blood was sampled daily for 10 days. The time of sampling depended on whether the patients were dialysed in the morning or afternoon but was always within 5 h of the last dose of paracetamol. On dialysis days samples were taken at the start of the session. The mean plasma concentration of paracetamol was 6.8 mg x l-1 after the first 24 h and subsequently varied little throughout the 10 days. Apparent steady-state plasma concentrations of 60.0 mg x l-1 and 54.5 mg x l-1 were reached for the glucuronide and sulphate conjugate of paracetamol respectively by the 2nd day of treatment with little variation throughout the remainder of the study. These steady-state concentrations of paracetamol glucuronide and sulphate were much lower than predicted. The steady-state plasma concentrations of the retained cysteine and mercapturate conjugates of paracetamol were low (5.7 and 3.7 mg x l-1, respectively) and there was no evidence of accumulation of these potentially toxic metabolites. It is not clear why regular dosing with paracetamol in haemodialysis patients did not cause the accumulation of paracetamol glucuronide or sulphate as predicted. There may be enterohepatic elimination of retained paracetamol conjugates or depletion of substrates such as inorganic sulphate during chronic dosing.

Paracetamol poisoning in children and hepatotoxicity

1. Paracetamol is one of the most common drugs that children accidentally ingest. Unlike the situation in adults, death and hepatotoxicity in children from paracetamol poisoning are exceedingly uncommon events. A review of the literature has revealed only seven deaths and fourteen cases of hepatotoxicity in children, with most of the cases resulting from chronic poisoning and not acute poisoning. 2. Children may be less prone to paracetamol hepatotoxicity because of developmental differences in the drug's metabolism and its pathways of detoxification. In the therapeutic setting of treatment of fever and pain in children, paracetamol is regarded as a drug with a higher therapeutic index, and as such, there seems to be little concern with strict adherence to dosage regimes. 3. Scrutiny of the above paediatric cases associated with chronic paracetamol poisoning suggests that the margin of safety of frequent therapeutic doses of paracetamol in infants and young children to be a lot lower than previously appreciated. This review highlights the need to re-evaluate the safety of paracetamol in the context of chronic therapy in infants and young children.

The disposition of paracetamol and the accumulation of its glucuronide and sulphate conjugates during multiple dosing in patients with chronic renal failure

We have compared the disposition of oral paracetamol (1.0 g t.d.s. for 10 days) in 6 healthy volunteers and 6 conservatively-managed patients with chronic renal failure (mean plasma creatinine 451 mumol.l-1). Blood was sampled daily for 10 days before the morning dose of paracetamol. Each day the pretreatment plasma concentrations of paracetamol were higher in the renal failure patients than in the volunteers, with mean values over the 10 days of 3.1 and 1.1 mg.l-1 respectively. The mean daily plasma concentrations of the sulphate and glucuronide conjugates of paracetamol were markedly higher in the renal failure group and apparent steady-state concentrations of about 25 and 85 mg.l-1 were reached on the 2nd and 6th days respectively. The mean steady-state plasma concentrations of the glucuronide conjugate on the 7th to 10th days of treatment were positively correlated with the plasma creatinine concentration (r = 0.97), but this relationship did not hold for the sulphate conjugate. Cysteine and mercapturate conjugates could only be detected in one patient. Predictions of steady-state concentrations based on previous studies with single doses of paracetamol in renal failure patients were remarkably accurate for the glucuronide but not for the sulphate conjugate. These results are consistent with some extra-renal elimination of retained paracetamol conjugates in patients with chronic renal failure, with limited regeneration of the parent compound. The sulphate metabolite did not accumulate as predicted, possibly because of depletion of inorganic sulphate.

The effect of therapeutic doses of paracetamol on sulphur metabolism in man

1. This study was designed to investigate the effect of prolonged paracetamol intake on sulphur metabolism in patients. Six patients, taking paracetamol in doses of 2-4 g d-1 and one taking 12 g d-1 took part in the study. Daily (24-h) collections of urine, and also plasma samples from these patients were analysed and in one case a study with additional methionine was performed. 2. The patients showed variable decrease in urinary output of inorganic sulphate but moderately raised plasma levels of inorganic sulphate. 3. Paracetamol metabolism was characterized by dominance of the glucuronidation pathway with the increase of the administered dose of paracetamol. Methionine added to the diet did not change this metabolic pattern. None of the subjects produced more than 0.6 mmol h-1 paracetamol sulphate while total sulphur excretion was 7.5-26.7 mmol d-1. 4. Volunteers taking 3 g d-1 paracetamol were also studied. 5. In persons taking a normal western diet containing over 20 mmol d-1 sulphur amino-acids paracetamol metabolism will not lead to sulphur amino-acid depletion even if high daily doses are used.

Circadian rhythm of serum sulfate levels in man and acetaminophen pharmacokinetics

The circadian variation of serum inorganic sulfate levels was studied in healthy volunteers. The effect of subchronic acetaminophen administration (650 mg q.i.d. for 4 days) on serum inorganic sulfate levels was investigated and the possible role of fluctuating serum inorganic sulfate levels on the pharmacokinetics of acetaminophen was evaluated. During a 24 h cycle, serum inorganic sulfate levels were lowest in the morning (11.00 h) and typically increased in the afternoon to reach a maximum in the early evening (19.00 h). Average 24 h serum concentrations were 360 microM and the difference between minimum and maximum levels was on average 25.8%. Subchronic administration of acetaminophen (650 mg q.i.d. for 4 days) significantly reduced serum inorganic sulfate levels to a 24 h average of 253 microM. The circadian rhythm, however, was not affected and the difference between minimum (12.00 h) and maximum (18.50 h) serum concentrations was 31.3%. Subchronic acetaminophen administration lead to a significant decrease in the renal excretion (-51%) and renal clearance (-33%) of inorganic sulfate. No significant differences were found in the disposition kinetics of acetaminophen and its glucuronide and sulfate conjugates during two consecutive dosing intervals (08.00-14.00 h, 14.00-20.00 h) on Day 4 of the acetaminophen regimen.

Pharmacokinetic drug interactions with oral contraceptives

Oral contraceptive steroids are used by an estimated 60 to 70 million women world-wide. Over the past 20 years there have been both case reports and clinical studies on the topic of drug interactions with these agents. Some of the interactions are of definite therapeutic relevance, whereas others can be discounted as being of no clinical significance. Pharmacological interactions between oral contraceptive steroids and other compounds may be of 2 kinds: (a) drugs may impair the efficacy of oral contraceptive steroids, leading to breakthrough bleeding and pregnancy (in a few cases, the activity of the contraceptive is enhanced); (b) oral contraceptive steroids may interfere with the metabolism of other drugs. A number of anticonvulsants (phenobarbital, phenytoin, carbamazepine) are enzyme-inducing agents and thereby increase the clearance of the oral contraceptive steroids. Valproic acid has no enzyme-inducing properties, and thus women on this anticonvulsant can rely on their low dose oral contraceptive steroids for contraceptive protection. Researchers are now beginning to unravel the molecular basis of this interaction, with evidence of specific forms of cytochrome P450 (P450IIC and IIIA gene families) being induced by phenobarbital. Rifampicin, the antituberculous drug, also induces a cytochrome P450 which is a product of the P450IIIA gene subfamily. This isozyme is one of the major forms involved in 2-hydroxylation of ethinylestradiol. Broad spectrum antibiotics have been implicated in causing pill failure; case reports document the interaction, and general practitioners are convinced that it is real. The problem remains that there is still no firm clinical pharmacokinetic evidence which indicates that blood concentrations of oral contraceptive steroids are altered by antibiotics. However, perhaps this should not be a surprise, given that the incidence of the interaction may be very low. It is suggested that an individual at risk will have a low bioavailability of ethinylestradiol, a large enterohepatic recirculation and gut flora particularly susceptible to the antibiotic being used. Two drugs, ascorbic acid (vitamin C) and paracetamol (acetaminophen), give rise to increased blood concentrations of ethinylestradiol due to competition for sulphation. The interactions could have some significance to women on oral contraceptive steroids who regularly take high doses of either drug. Although on theoretical grounds adsorbents (e.g. magnesium trisilicate, aLuminium hydroxide, activated charcoal and kaolin) could be expected to interfere with oral contraceptive efficacy, there is no firm evidence that this is the case. Similarly, there is no evidence that smoking alters the pharmacokinetics of oral contraceptive steroids. These agents are now well documented as being able to alter the pharmacokinetics of other concomitantly administered drugs.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of chronic paracetamol administration to rats on the glycosaminoglycan content of patellar cartilage

Male Wistar rats were treated with paracetamol (200 mg/kg twice a day) for 2, 3, 4 and 9 weeks. During the first four weeks of paracetamol administration the serum sulfate concentration was significantly decreased. However, during the fourth until the ninth week, the serum sulfate concentration was only diminished to a small and insignificant extent. The paracetamol administration did not lead to serious liver or renal toxicity, as determined by alanine aminotransferase and creatinine levels in the serum of the rats. The paracetamol-induced serum sulfate depletion, observed during the first four weeks of the experiment, led to a significantly lower glycosaminoglycan content of the patellar cartilage of the rats after three and four weeks paracetamol treatment. When after the fourth week the serum sulfate concentration rose to nearly normal levels also the glycosaminoglycan content in the rat patellar cartilage reached control levels. These data indicate that the serum sulfate depletion might be the causative factor for the observed reduction in glycosaminoglycan content of rat patellar cartilage.

Decrease of inorganic blood sulfate following treatment with selected antirheumatic drugs: potential consequence for articular cartilage

The elimination kinetics of inorganic blood sulfate in mice was followed for four hours after a single, oral administration of an antirheumatic drug. Sodium salicylate, aspirin, diflunisal and benorylate, all in a dose of 1.25 mmol/kg, reduced the sulfate level to the less than half that of control. This phenomenon was also demonstrated by phenylbutazone, oxyphenbutazone (both 1 mmol/kg), chloroquine diphosphate (0.6 mmol/kg) and tiaprofenic acid (0.02-0.35 mmol/kg). Niflumic acid (1.08 mmol/kg), piroxicam (0.03 mmol/kg), indomethacin (6.10(-3) mmol/kg), diclofenac (5.10(-3) mmol/kg), ketoprofen (0.2 mmol/kg), naproxen (0.08 mmol/kg) and ibuprofen (0.24 mmol/kg) possessed no sulfate lowering properties. The potential relevance of the use of sulfate lowering drugs for articular cartilage integrity is discussed in the light of what is already known about this subject.

Review: first-pass metabolism by the gastrointestinal mucosa

The bioavailability of orally administered drugs may be reduced due to presystemic elimination. The first-pass effect can occur in the gastrointestinal tract, the liver and lung. Although the liver is the main drug metabolizing organ in the body, the gut wall can play an important role in the first-pass metabolism of certain drugs. Both phase I (preconjugation) and phase II (conjugation) reactions have been described. However, while the oxidative metabolic capacity of the intestinal mucosa is considerably smaller than that of the liver, the activity of conjugation reactions in the gut may be close to that of the liver, and in some cases may exceed it. Sulphate conjugation is particularly important for steriod hormones such as ethinyloestradiol, and for the beta-adrenoceptor stimulants isoprenaline and isoetharine. Glucuronidation has been demonstrated to occur in man for morphine, paracetamol and oestrogens. Significant drug--drug interactions have been described involving drugs undergoing sulphate conjugation. The study of intestinal metabolism in vivo is difficult in man since direct methods (for example, hepatic portal vein catheterization) is justified in only a small number of patients. Therefore, much of our present understanding has been derived from various in-vitro studies involving intestinal sheets, mucosal biopsies, isolated enterocytes and microsomal preparations.

Paracetamol interaction with oral contraceptive steroids: increased plasma concentrations of ethinyloestradiol

The effect of a single dose of paracetamol (1 g) on plasma concentrations of the oral contraceptive steroids ethinyloestradiol (EE2) and levonorgestrel (LNG) has been studied in six healthy female volunteers. The area under the plasma concentration-time curve (AUC0-24) of EE2 was significantly increased following paracetamol administration by 22% (control 2221 +/- 291; following paracetamol, 2702 +/- 452 pg ml-1 h; mean +/- s.d.; P less than or equal to 0.05). The greatest effect was evident in the time period 0-3 h. There was a significant decrease in the AUC of EE2-sulphate after paracetamol (7736 +/- 3791 pg ml-1 h) compared with control (13161 +/- 4535 pg ml-1 h; P less than or equal to 0.05). Plasma concentrations of LNG were unaltered by concurrent paracetamol administration. We conclude that the administration of a single 1 g dose of paracetamol causes an increase in plasma concentrations of EE2 as a result of a reduction in the sulphation of the steroid. This interaction may be of clinical significance in women on oral contraceptive steroids who regularly take paracetamol.