Paracetamol elimination in patients with non-insulin dependent diabetes mellitus

Why paracetamol (acetaminophen) is a suitable first choice for treating mild to moderate acute pain in adults with liver, kidney or cardiovascular disease, gastrointestinal disorders, asthma, or who are older

Acute pain is among the most common reasons that people consult primary care physicians, who must weigh benefits versus risks of analgesics use for each patient. Paracetamol (acetaminophen) is a first-choice analgesic for many adults with mild to moderate acute pain, is generally well tolerated at recommended doses (≤4 g/day) in healthy adults and may be preferable to non-steroidal anti-inflammatory drugs that are associated with undesirable gastrointestinal, renal, and cardiovascular effects. Although paracetamol is widely used, many patients and physicians still have questions about its suitability and dosing, especially for older people or adults with underlying comorbidities, for whom there are limited clinical data or evidence-based guidelines. Inappropriate use may increase the risks of both overdosing and inadequate analgesia. To address knowledge deficits and augment existing guidance in salient areas of uncertainty, we have researched, reviewed, and collated published evidence and expert opinion relevant to the acute use of paracetamol by adults with liver, kidney, or cardiovascular diseases, gastrointestinal disorders, asthma, or/and who are older. A concern is hepatotoxicity, but this is rare among adults who use paracetamol as directed, including people with cirrhotic liver disease. Putative epidemiologic associations of paracetamol use with kidney or cardiovascular disease, hypertension, gastrointestinal disorders, and asthma largely reflect confounding biases and are of doubtful relevance to short-term use (<14 days). Paracetamol is a suitable first-line analgesic for mild to moderate acute pain in many adults with liver, kidney or cardiovascular disease, gastrointestinal disorders, asthma, and/or who are older. No evidence supports routine dose reduction for older people. Rather, dosing for adults who are older and/or have decompensated cirrhosis, advanced kidney failure, or analgesic-induced asthma that is known to be cross-sensitive to paracetamol, should be individualized in consultation with their physician, who may recommend a lower effective dose appropriate to the circumstances.

Type 2 diabetes mellitus and osteoarthritis

OBJECTIVES

Type 2 diabetes mellitus (T2DM) and osteoarthritis (OA) are common diseases that frequently co-exist, along with overweight/obesity. While the mechanical impact of excess body weight on joints may explain lower limb OA, we sought to explore whether T2DM is linked to OA outside of excess weight and whether T2DM may play a role in OA pathophysiology. The consequence of T2DM on OA outcomes is a question of research interest.

METHODS

We conducted a critical review of the literature to explore the association between T2DM and OA, whether any association is site-specific for OA, and whether the presence of T2DM impacts on OA outcomes. We also reviewed the literature to assess the safety of anti-OA treatments in patients with T2DM.

RESULTS

T2DM has a pathogenic effect on OA through 2 major pathways involving oxidative stress and low-grade chronic inflammation resulting from chronic hyperglycemia and insulin resistance. T2DM is a risk factor for OA progression and has a negative impact on arthroplasty outcomes. Evidence is mounting for safety concerns with some of the most frequently prescribed anti-OA medications, including paracetamol, non-steroidal anti-inflammatory drugs, and corticosteroid injections, while other anti-OA medications may be safely prescribed in OA patients with T2DM, such as glucosamine and intra-articular hyaluronic acid.

CONCLUSIONS

Future research is needed to better understand whether diabetes control and prevention can modulate OA occurrence and progression. The selection of therapy to treat OA symptoms in patients with T2DM may require careful consideration of the evidence based to avoid untoward safety issues.

Paracetamol in Older People: Towards Evidence-Based Dosing?

Paracetamol is the most commonly used analgesic in older people, and is mainly dosed according to empirical dosing guidelines. However, the pharmacokinetics and thereby the effects of paracetamol can be influenced by physiological changes occurring with ageing. To investigate the steps needed to reach more evidence-based paracetamol dosing regimens in older people, we applied the concepts used in the paediatric study decision tree. A search was performed to retrieve studies on paracetamol pharmacokinetics and safety in older people (> 60 years) or studies that performed a (sub) analysis of pharmacokinetics and/or safety in older people. Of 6088 articles identified, 259 articles were retained after title and abstract screening. Further abstract and full-text screening identified 27 studies, of which 20 described pharmacokinetics and seven safety. These studies revealed no changes in absorption with ageing. A decreased (3.9-22.9%) volume of distribution (Vd) in robust older subjects and a further decreased Vd (20.3%) in frail older compared with younger subjects was apparent. Like Vd, age and frailty decreased paracetamol clearance (29-45.7 and 37.5%) compared with younger subjects. Due to limited and heterogeneous evidence, it was difficult to draw firm and meaningful conclusions on changed risk for paracetamol safety in older people. This review is a first step towards bridging knowledge gaps to move to evidence-based paracetamol dosing in older subjects. Remaining knowledge gaps are safety when using therapeutic dosages, pharmacokinetics changes in frail older people, and to what extent changes in paracetamol pharmacokinetics should lead to a change in dosage in frail and robust older people.

Influence of the Time of Intravenous Administration of Paracetamol on its Pharmacokinetics and Ocular Disposition in Rabbits

BACKGROUND AND OBJECTIVES

Paracetamol is one of the most common analgesics and antipyretics applied in health care. The aim of the study was to investigate the influence of the time-of-day administration on the paracetamol pharmacokinetics and its penetration into aqueous humour (AH).

METHODS

Rabbits were divided into three groups: I-receiving paracetamol at 08.00 h, II-receiving paracetamol at 16.00 h, and III-receiving paracetamol at 24.00 h. Paracetamol was administered intravenously at a single dose of 35 mg/kg. The concentrations of paracetamol and its metabolite (paracetamol glucuronide) in the plasma, as well as in AH were measured with the validated HPLC-UV method.

RESULTS

No significant differences in the pharmacokinetic parameters of paracetamol was observed. When the drug was administered at 24.00 h,  elimination half-life (t _1/2kel) of paracetamol glucuronide was longer than when the drug was administered 08.00 h (P = 0.0193). In addition, a statistically significant increase in the paracetamol glucuronide/paracetamol ratio was observed when the drug was administered at 08.00 vs. 16.00 h (P ≤ 0.0001) and 24.00 h (P ≤ 0.0001).

CONCLUSIONS

There was no chronobiological effect on the pharmacokinetic parameters of paracetamol.

Differences in the single-oral-dose pharmacokinetics and urinary excretion of paracetamol and its conjugates between Hong Kong Chinese and Caucasian subjects

BACKGROUND AND OBJECTIVES

The present study was conducted to determine if ethnic differences exist for single oral dose pharmacokinetics of paracetamol and its conjugates between Hong Kong Chinese and Caucasian subjects.

METHODS

Twenty healthy Chinese (n = 11) and Caucasian (n = 9) subjects, aged 21-44 years, 11 male and nine female, were given oral paracetamol syrup 20 mg/kg, following an overnight fast. Paracetamol and its metabolites (glucuronide, sulphate, cysteine and mercapturic acid conjugates) were measured in serial plasma samples (0.25, 0.5, 0.75, 1.0, 1.5, 2, 3,...,12, 24 h) and urine collections (0-24 h) by high-performance liquid chromatography.

RESULTS

In Chinese subjects, the (mean range) peak plasma concentration of paracetamol was 23.8 mug/mL (17.9-32.3) and time to attain this peak 0.66 h (0.5-0.75). This was lower (P < 0.015) at 18.7 microg/mL (14.4-22.9) and achieved later (P < 0.033) at 1.06 h (0.5-2.0) in Caucasians. In Chinese subjects, plasma levels of glucuronide were lower, sulphate higher and cysteine conjugates significantly lower than in Caucasians (P < 0.05). Chinese subjects excreted 6% more sulphate and 5% less glucuronide. They also excreted significantly less mercapturic acid conjugates (P < 0.001).

DISCUSSION AND CONCLUSION

Chinese subjects show more rapid absorption of paracetamol, a tendency to produce less glucuronide but more sulphate conjugates and reduced production of cysteine and mercapturic acid conjugates. The latter may help to protect against hepatotoxicity following paracetamol overdose.

Pediatric intravenous paracetamol (propacetamol) pharmacokinetics: a population analysis

BACKGROUND

The aim of this study was to describe propacetamol pharmacokinetics in children in order to predict concentrations after a standard dosing regimen of propacetamol 30 mg x kg(-1) (15 mg x kg(-1) paracetamol) 6 h.

METHODS

A population pharmacokinetic analysis of paracetamol time-concentration profiles (846 observations) from 144 children [postconception age (PCA) 27 weeks-14 years] was undertaken using nonlinear mixed effects models (NONMEM). These data were taken from seven separate studies involving children given intravenous propacetamol. Time-concentration profiles (503 observations) from a further 86 children (PCA: 37 weeks-14 years) given paracetamol elixir orally were included in the analysis to assess relative bioavailability of intravenous propacetamol.

RESULTS

A three-compartment (depot, central and peripheral) linear disposition model fitted data better than a two-compartment (depot and central) model. Population parameter estimates (between subject variability, %) were central volume (V2/F(oral)) 24 (55%) l x 70 kg(-1), peripheral volume of distribution (V3/F(oral)) 30 (32%) l x 70 kg(-1), clearance (CL/F(oral)) 16 (40%) l x h(-1) x 70 kg(-1) and intercompartment clearance (Q/F(oral)) 55 (116%) l x h(-1) x 70 kg(-1). Clearance increased from 27 weeks PCA (1.87 l x h(-1) 70 kg(-1)) to reach 84% of the mature value by 1 year of age (standardized to a 70 kg person using allometric '1/4 power' models). Peripheral volume of distribution decreased from 27 weeks PCA (45.0 l x 70 kg(-1)) to reach 110% of its mature value by 6 months of age. Central volume of distribution and intercompartment clearance did not change with age. Between occasions variability for the peripheral volume of distribution (V3/F(oral)) and clearance (CL/F(oral)) were 18.5 and 19.3%, respectively. A rate constant representing hydrolysis of propacetamol to paracetamol (K(a) 96 h(-1)) was size related, but not age related. The relative bioavailability of intravenous propacetamol compared with an oral elixir was 0.5.

CONCLUSIONS

A mean paracetamol serum concentration of 10 mg x l(-1) is achieved in children 2-15 years given a standard dose of propacetamol 30 mg x kg(-1) 6 h. This concentration in the effect compartment is associated with a pain reduction of 2.6/10 after tonsillectomy and provides satisfactory analgesia for mild to moderate pain. Clearance is reduced in children less than 1 year of age and the target concentration of 10 mg x l(-1) may be achieved by scaling this standard dose regimen using predicted clearance in this younger age group.

Pharmacokinetics of intravenous paracetamol in children and adolescents under major surgery

BACKGROUND

The aim of this study was to describe the pharmacokinetics of paracetamol (acetaminophen) and to get primary information on its metabolism after first indicated intravenous administration of paracetamol in children and adolescents undergoing major surgery.

METHODS

About 4 weeks after the last chemotherapy, seven children and adolescents (five osteosarcoma, two Ewing tumors) received paracetamol infusion (median: 15.0 mg/kg) for analgesia. Sparse serum (37 samples; 4-7 per patient) and urine samples (27 samples; 0-15 per patient) were analyzed for paracetamol, paracetamol-glucuronide, paracetamol-sulfate, paracetamol-mercapturate and paracetamol-cysteine using capillary electrophoresis. Nonlinear mixed-effect models were used to describe the pharmacokinetics of paracetamol in plasma.

RESULTS

Pharmacokinetics of paracetamol after intravenous administration was best described by a two-compartment model with clearance of 13.2 l/h per 70 kg (between-subject variability: 30%), intercompartmental clearance of 45.7 l/h per 70 kg (both parameters standardized to a 70-kg person using allometric "1/4 power models"), central volume of distribution of 13.2 l per 70 kg (between-subject variability: 71%) and peripheral volume of distribution of 33.0 l per 70 kg. Paracetamol, the glucuronide- and sulfate conjugates as well as cysteine and mercapturic acid conjugates, both products of oxidative pathways of paracetamol, were excreted in urine.

CONCLUSIONS

Surgery, with all its potential influencing factors, together with chemotherapy given about 4 weeks previously do not seem to have a major impact on the pharmacokinetic behavior and the between-subject variability of paracetamol after intravenous administration.

Human variability for metabolic pathways with limited data (CYP2A6, CYP2C9, CYP2E1, ADH, esterases, glycine and sulphate conjugation)

Human variability in the kinetics of a number of phase I (CYP2A6, CYP2C9, CYP2E1, alcohol dehydrogenase and hydrolysis) and phase II enzymes (glycine and sulphate conjugation) was analysed using probe substrates metabolised extensively (>60%) by these routes. Published pharmacokinetic studies (after oral and intravenous dosing) in healthy adults and available data on subgroups of the population (effects of ethnicity, age and disease) were abstracted using parameters relating primarily to chronic exposure [metabolic and total clearances, area under the plasma concentration time-curve (AUC)] and acute exposure (C(max)). Interindividual differences in kinetics for all these pathways were low in healthy adults ranging from 21 to 34%. Pathway-related uncertainty factors to cover the 95th, 97.5th and 99th centiles of healthy adults were derived for each metabolic route and were all below the 3.16 kinetic default uncertainty factor in healthy adults, with the possible exception of CYP2C9*3/*3 poor metabolisers (based on a very limited number of subjects). Previous analyses of other pathways have shown that neonates represent the most susceptible subgroup and this was true also for glycine conjugation for which an uncertainty factor of 29 would be required to cover 99% of this subgroup. Neonatal data were not available for any other pathway analysed.

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.

Human variability in glucuronidation in relation to uncertainty factors for risk assessment

The appropriateness of the default uncertainty factor for human variability in kinetics has been investigated for glucuronidation using an extensive database of substrates metabolised primarily by this pathway. Inter-individual variability was quantified for 15 compounds from published pharmacokinetic studies (after oral and intravenous dosing) in healthy adults and other subgroups using parameters relating to chronic exposure (metabolic and total clearances, area under the plasma concentration time-curve (AUC)) and acute exposure (C(max)). Low inter-individual variability (about 30-35%) was found for all parameters (clearance corrected or not corrected for body weight, metabolic clearance, oral AUC and C(max)) after either iv or oral administration to healthy adults. The overall variability of 31% for glucuronidation in healthy adults supported the validity of the default kinetic uncertainty factor of 3.16 for this group, because it would cover more than 99% of individuals. Comparisons between potentially sensitive subgroups and healthy adults using differences in means and variability indicated that neonates showed the greatest impairment of glucuronidation, and that the 3.16 kinetic default factor applied to the mean data for adults would be inadequate for this subpopulation. The in vivo data have been used to derive pathway-related default factors for compounds eliminated largely via glucuronidation.

Paracetamol metabolism in patients with ulcerative colitis

AIMS

The capacity for sulphation of phenols appears to be impaired in the colonic mucosa of patients with ulcerative colitis. The aim of the present study was to investigate the systemic capacity for sulphation of phenols in patients with ulcerative colitis assessed by the metabolic clearances of paracetamol to the sulphate, glucuronide and glutathione derived metabolites.

METHODS

Ten patients with ulcerative colitis and 10 control subjects received a single oral dose of paracetamol (1 g). Venous blood samples were collected frequently for pharmacokinetic determinations (one compartment model). Urine was collected for 24 h. Plasma samples were analysed for parent drug and urine samples for parent drug and metabolites by h.p.l.c. Partial metabolic clearances were calculated as the fractional urinary recovery of each conjugate multiplied by the apparent oral clearance of paracetamol.

RESULTS

The apparent oral clearance of paracetamol and the partial clearances of its metabolites were not significantly different between the two study groups. Median value and the corresponding 25th and 75th percentiles for the clearance of the sulphate metabolites were 93.6 (82.5-138.8) ml kg(-1)h(-1) and 77.4 (75.5-99.1), patients with ulcerative colitis and control subjects, respectively.

CONCLUSIONS

These results do not indicate a general impairment of the systemic capacity for sulphation of paracetamol in patients with ulcerative colitis.