Unaltered etanercept pharmacokinetics with concurrent methotrexate in patients with rheumatoid arthritis

The purpose of this study was to evaluate the potential impact of concurrent weekly oral methotrexate administration on the pharmacokinetics of etanercept in patients with rheumatoid arthritis (RA) in a phase 3B trial. As part of a double-blind randomized trial of 682 patients with rheumatoid arthritis who received etanercept (25 mg subcutaneously twice weekly), methotrexate (weekly oral dose, median weekly dose: 20 mg), or etanercept (25 mg subcutaneously twice weekly) plus methotrexate (weekly oral dose, median weekly dose: 20 mg), serum etanercept concentrations were measured in a subset of patients. Serum samples for 98 randomly selected patients (48 receiving etanercept-alone treatment, 50 receiving etanercept plus methotrexate combination treatment) were analyzed to assess the pharmacokinetics of etanercept. A single blood sample was drawn from each patient at baseline and at the week 24 visit. Given the variable sampling time for patients in both groups, a population pharmacokinetic analysis using NONMEM was conducted for etanercept. A final covariate population pharmacokinetic model was constructed based on previously obtained etanercept data from both healthy subjects (n = 53) and patients with RA (n = 212) in 10 prior clinical trials. The predictive performance of the final model was assessed by both bootstrap and data-splitting validation approaches. The final model was then used to estimate Bayesian pharmacokinetic parameters for the patients in both treatments in the current trial. The potential effect of the concurrent administration of methotrexate on the pharmacokinetics of etanercept was examined by comparing the clearance values between 2 treatments using statistical criteria. A population 2-compartment model with first-order elimination from the central compartment and with either zero-order (intravenous administration) or first-order (subcutaneous administration) input was selected based on the data from the prior 10 etanercept clinical studies. The following pharmacokinetic parameters (typical value +/- standard error) were estimated: clearance (CL: 0.072 +/- 0.005 L/h), volume of distribution in the central compartment (V(c): 5.97 +/- 0.45 L), volume of distribution in the peripheral compartment (V(p): 2.05 +/- 0.32 L), intercompartment clearance (Q: 0.0645 +/- 0.0093 L/h), first-order absorption rate constant (k(a): 0.0282 +/- 0.0039 1/h), and absolute bioavailability for subcutaneous administration (F: 0.626 +/- 0.056). Interindividual variability of the pharmacokinetic parameters was quantified for CL (25.1%), V(c) (41.7%), k(a) (53.1%), and F (24.2%). Residual variability consisted of combined additive (11.4 ng/mL) and proportional error (49.9%). Both age (< 17 years) and body weight (< 60 kg) were found to be important covariates on CL. The results of both validation tests indicated the adequate predictive performance of the population model. Based on the bioequivalence criteria, the Bayesian-estimated clearance for patients receiving etanercept alone (mean: 0.070 L/h) was comparable to that for patients receiving a combination of etanercept and methotrexate (mean = 0.066 L/h). The pharmacokinetics of etanercept were not altered by the concurrent administration of methotrexate in patients with rheumatoid arthritis. Thus, no etanercept dose adjustment is needed for patients taking concurrent methotrexate.     

雷腾舒治疗甲氨蝶呤反应不足类风湿关节炎患者群体药动学研究

目的:建立群体药代动力学(PPK)模型,探讨群体药代动力参数与有效性和安全性之间的关系.方法:采用非线性混合效应模型,建立雷腾舒的PPK模型,评估PPK对临床的安全性及有效性的影响.结果:模型能较好地拟合雷腾舒的血药浓度,参数估计稳健.研究发现血红蛋白(HBG)水平越高,雷腾舒的清除率越高.药效方面,ACR20与雷腾舒的体内暴露程度显著相关(P<0.05).安全性方面,雷腾舒体内暴露与不良反应、育龄妇女生殖系统不良反应相关性不显著.结论:本研究所建立的群体药动学模型能较好地描述雷腾舒在患者中的药动学特征.雷腾舒的暴露量与ACR20相关性显著、与生殖系统不良反应呈现一定相关性.     

Salicylate pharmacokinetics in patients with rheumatoid arthritis.

1. The pharmacokinetics of salicylic acid (SA) and its major metabolite salicyluric acid (SU) were studied in nine patients with rheumatoid arthritis following a 900 mg oral dose of acetylsalicylic acid and during 6 weeks of chronic administration of enteric coated aspirin (3,900 mg day). Response to therapy was also monitored. 2. The various pharmacokinetic parameters determined in the study were similar to those observed in other single dose salicylate studies amongst healthy volunteers but were not predictive of salicylate concentration in the chronic dose study. 3. Plasma concentrations of SA (total and unbound) were found to decline significantly over the 6 weeks and plasma SU concentrations increased. 4. During the chronic dosing study, there was a significant increase in the Vmax (total and unbound) for the formation of SU, whilst the Km and SU clearance remained constant. Also, the elimination rate constant (k) for salicylate was not significantly affected. 5. Therapeutic response to salicylate therapy was not significantly affected by the decline in SA concentrations.     

Tocilizumab has no clinically relevant effects on methotrexate pharmacokinetics in patients with rheumatoid arthritis

Objective: To assess the effects of tocilizumab on methotrexate and 7-hydroxymethotrexate pharmacokinetics in patients with rheumatoid arthritis and to explore the pharmacodynamic effect of tocilizumab on C-reactive protein (CRP), a marker of inflammation. Methods: Methotrexate (10 - 25 mg) was administered orally on Days 1, 8, 15, 22, 29, 36, and 43. On Day 8 patients received 10 mg/kg tocilizumab intravenously. Blood samples for pharmacokinetic analyses were collected on Days 1, 15, and 43 and for pharmacodynamics (CRP) throughout the study. Results: 90% CIs for mean effect ratios (Day 15/Day 1 and Day 43/Day 1) of methotrexate and 7-hydroxymethotrexate (AUClast and Cmax) were close to or within the bioequivalence boundaries (80 - 125%). CRP normalized within 1 week after tocilizumab injection and remained within normal limits for 3 weeks. Conclusion: Tocilizumab and methotrexate can be administered concurrently without dosage adjustments.     

Monitoring methotrexate therapy in patients with rheumatoid arthritis

OBJECTIVE: The aim of this work was to study methotrexate (MTX) kinetics and their relation to the effectiveness of the therapy in patients with rheumatoid arthritis (RA). Other aims were to analyze the influence of MTX on liver, kidney, hematopoietic function and to determine the possibility of using early drug concentrations to predict the subsequent value of the treatment. MATERIAL AND METHODS: The observations were carried out in 49 patients with RA after the first dose of MTX and after 7 months of treatment. Methotrexate concentrations in blood serum and urine were determined using fluorescence polarization immunoassay applying a TDx Abbott analyzer. RESULTS: No correlation between concentrations, pharmacokinetic parameters and the duration of the disease, its activity, clinical symptoms, observations pertaining to the disease made by physician and patients and morning stiffness of joints was seen. Of those tests for the evaluation of liver, kidney and hematopoietic function, only the mean activity of N-acetyl-beta-D-glucosaminidase (NAG) in urine was significantly elevated both before and after treatment with MTX when compared to corresponding values in the control group of healthy subjects. We have formulated equations allowing for the early recognition of patients with a risk of adverse effects due to impaired elimination of MTX from the body. CONCLUSION: Our results show that monitoring MTX therapy using concentrations in patients with RA does not significantly improve the effectiveness of the treatment, but it can play an important role in increasing the safety of this drug.     

The pharmacokinetics of flurbiprofen in younger and elderly patients with rheumatoid arthritis.

The pharmacokinetics of flurbiprofen (Ansaid Tablets, Upjohn Company of Canada, Don Mills, Ontario) were evaluated in both younger (40 to 60 years) and elderly (65 to 83 years) rheumatoid arthritic patients after both a 100-mg single-dose administration and at steady state during a 100-mg twice-a-day dosage regimen. Both flurbiprofen plasma concentration-time profiles and the urinary excretion of flurbiprofen and its major metabolites were evaluated. The results indicate that the pharmacokinetics of flurbiprofen are linear in both age groups based on only minor changes between single-dose and steady-state parameter determinations and the agreement between calculated and predicted accumulation values in plasma concentrations. Only minor differences in the pharmacokinetic parameters were observed between the younger and elderly patients. Only free flurbiprofen clearance was found to have a significant but variable correlation to patient age. The effect of flurbiprofen on the urinary excretion of two prostaglandins were also evaluated throughout this study. In both age groups, the maximum decrease in urinary excretion was observed after the first dose, and this effect was maintained throughout the remainder of the study. Percent decreases from baseline in urinary excretion during drug administration were similar for both age groups. Similar side-effect profiles were observed between age groups.     

The pharmacokinetics of isoxicam in elderly patients with rheumatoid arthritis

Nineteen patients, aged 60 years and over, with rheumatoid arthritis participated in a clinical trial to investigate the pharmacokinetics of isoxicam (a new non-steroidal anti-inflammatory drug) in this age group. The purpose of the study was to determine if the pharmacokinetics are different compared to a younger healthy population. The half-lives were independent of dosage, indicating linearity of pharmacokinetics. Furthermore, the half-lives after repeated dosing were not different from those found after single doses of 400 mg. This shows that there is neither undue accumulation of the drug nor induction of its own metabolism. These results are similar to the results obtained in other centres when isoxicam was administered to healthy subjects between 18 and 32 years.     

The pharmacokinetics of the enantiomers of flurbiprofen in patients with rheumatoid arthritis.

Plasma and synovial fluid concentrations of the enantiomers of flurbiprofen were measured in 15 rheumatoid patients receiving 100 mg racemic flurbiprofen twice daily. Pharmacokinetic parameters showed considerable variability within the group of patients, although differences in S(+)/R(-) plasma concentration ratios were small. The average values (+/- s.d.) of oral plasma clearance, volume of distribution and elimination half-life for R(-)-flurbiprofen were 0.075 (+/- 0.066) l min-1, 12.47 (+/- 5.79) l and 138 (+/- 61) min, respectively. The average values (+/- s.d.) of oral plasma clearance, volume of distribution and elimination half-life for S(+)-flurbiprofen were 0.057 (+/- 0.035) l min-1, 12.81 (+/- 4.43) l and 155 (+/- 49) min, respectively. S(+)/R(-) ratios (+/- s.d.) rose from 1.06 (+/- 0.12) to 1.75 (+/- 0.61) at the end of the 12 h interval in plasma and from 1.18 (+/- 0.13) to 1.47 (+/- 0.24) over the measured time course in synovial fluid. Increases in S(+)/R(-) ratios may be clinically important as they demonstrate accumulation of the pharmacologically active species.     

Fostamatinib, a Syk-kinase inhibitor, does not affect methotrexate pharmacokinetics in patients with rheumatoid arthritis

Fostamatinib (R788) is being investigated as an add-on therapy for the treatment of rheumatoid arthritis (RA) in patients with inadequate response to methotrexate (MTX). This study evaluated the potential pharmacokinetic interaction between R788 and MTX. Sixteen RA subjects on a stable weekly MTX regimen were enrolled and received MTX on days 1 and 8. Twelve subjects received 100 mg of R788 orally, and 4 subjects received a matching placebo twice daily from days 4 to 8 and once daily on days 3 and 9. Blood samples were collected on days 1 and 8 for MTX and 7-hydroxymethotrexate (7-OH-MTX), and days 3 and 9 for R788 and its active metabolite, R406. MTX and 7-OH-MTX pharmacokinetic parameters were similar on days 1 and 8. In the R788 group, the mean day 8 to day 1 ratios (90% confidence intervals) of maximum concentration and area under the plasma concentration-time curve estimates were 1.01 (0.85-1.20) and 1.12 (0.90-1.40) for MTX and 1.06 (0.82-1.35) and 1.06 (0.83-1.36) for 7-OH-MTX, respectively. Urinary excretion of MTX and 7-OH-MTX was also similar with or without R788, averaging 58% to 69% and 4% to 5% of the MTX dose, respectively. The data suggest that there is no clinically significant pharmacokinetic interaction of R788 and MTX in RA patients.     

Population pharmacokinetics of hydroxychloroquine in patients with rheumatoid arthritis

SUMMARY: Hydroxychloroquine (HCQ) is an antimalarial drug that is also used as a second-line treatment of rheumatoid arthritis (RA). Clinically, the use of HCQ is characterized by a long delay in the onset of action, and withdrawal of treatment is often a result of inefficacy rather than from toxicity. The slow onset of action can be attributed to the pharmacokinetics (PK) of HCQ, and wide interpatient variability is evident. Tentative relationships between concentration and effect have been made, but to date, no population PK model has been developed for HCQ. This study aimed to develop a population PK model including an estimation of the oral bioavailability of HCQ. In addition, the effects of the coadministration of methotrexate on the PK of HCQ were examined. Hydroxychloroquine blood concentration data were combined from previous pharmacokinetic studies in patients with rheumatoid arthritis. A total of 123 patients were studied, giving the data cohort from four previously published studies. Two groups of patients were included: 74 received hydroxychloroquine (HCQ) alone, and 49 received HCQ and methotrexate (MTX). All data analyses were carried out using the NONMEM program. A one-compartment PK model was supported, rather than a three-compartment model as previously published, probably because of the clustering of concentrations taken at the end of a dosing interval. The population estimate of bioavailability of 0.75 (0.07), n = 9, was consistent with literature values. The parameter values from the final model were: Cl = 9.9 +/- 0.4 L/h, V = 605 +/- 91 L, ka = 0.77 +/- 0.22 hours(-1), t(tag) = 0.44 +/- 0.02 hours. Clearance was not affected by the presence of MTX, and, hence, steady-state drug concentrations and maintenance dosage requirements were similar. A population PK model was successfully developed for HCQ.     

First dose and steady-state pharmacokinetics of oxcarbazepine and its 10-hydroxy metabolite

Summary The pharmacokinetics of oxcarbazepine (a new anticonvulsant which is a congener of carbamazepine) and of its 10-hydroxy metabolite were studied at the outset of therapy in 8 adult epileptics comedicated with other anticonvulsants. The pharmacokinetic study was repeated under steady-state conditions after 3 months of drug intake in 6 of these subjects.The plasma elimination half-life of oxcarbazepine appeared to lie in the range 1.0–2.5 h, and that of its 10-hydroxy metabolite averaged 8.4 h. The apparent oral clearance of the parent drug (averaging 2.51·kg^–1·h^–1) was high enough to suggest substantial presystemic elimination. The oral clearance fell after 3 months of drug intake, but the half-lives of the drug and metabolite showed no statistically significant change over this time. Steady-state plasma levels of both drug and metabolite were linearly related to drug dose, metabolite levels averaging 9 times those of the parent substance.     

Pharmacokinetics of low-dose methotrexate in rheumatoid arthritis patients

The pharmacokinetics and bioavailability of low-dose methotrexate (MTX) (10 mg/m2) were evaluated in 41 subjects who had definite or classical rheumatoid arthritis as defined by the American Rheumatism Association criteria. Subjects received 10 mg/m2 (to the nearest 2.5 mg) of MTX in a single oral dose and a single intravenous (iv) dose one week apart. Serum concentrations for this low-dose regimen were monitored using a radiochemical ligand binding assay. The results indicate the MTX is cleared from the plasma at a rate of 84.6 mL/min/m2. The terminal half-life was approximately 6 h. The volumes of distribution at steady state and for the central compartment were 22.2 and 13.5 L/m2, respectively. The mean residence time in the body, in the systemic circulation, and in the periphery were estimated to be 4.7, 3.0, and 1.7 h, respectively, with a peripheral single-pass mean transit time of 6.0 h and an intrinsic mean residence time in the periphery of 7.9 h. The mean absorption time was 1.2 h and the oral bioavailability was 0.70. The ratio of synovial fluid concentration to serum concentration 4 and 24 h after a dose was found to be approximately 1.0, indicating that at least within that time range serum and synovial fluid concentrations are approximately equal. Because of conflicting results and insufficient data from previous high-dose pharmacokinetic studies, it is difficult to say whether or not low-dose MTX pharmacokinetics differs from those of high-dose MTX.     

Salicyl phenolic glucuronide pharmacokinetics in patients with rheumatoid arthritis

Summary The pharmacokinetics of salicyl phenolic glucuronide (SPG) and other salicylic acid (SA) metabolites were studied at three aspirin dosage regimens in eight patients with rheumatoid arthritis. Each patient received 1, 2 and 4 g enteric coated aspirin (ASA) daily in ascending order. At the end of each 2-week dosage period, plasma and urine were collected over a dosage interval for the estimation of various pharmacokinetic parameters. With increasing ASA dosage, mean clearance of SA to SPG was approximately constant (1.8±0.3, 1.7±0.2, and 1.5±0.2 ml/min at 1, 2 and 4 g/day, respectively) when related to plasma concentrations of total SA. The percentage of the ASA dosage recovered in urine as SPG increased from 5.2±1.1 to 7.1±1.1 to 10.5±1.7 at 1, 2 and 4 g/day, respectively. It was concluded, however, that the conversion of SA to SPG is saturable, since the mean clearance of SA to SPG decreased when calculated with respect of the plasma concentration of unbound SA (13.4±1.6, 11.0±1.4, and 6.6±1.9 ml/min at 1, 2 and 4 g/day, respectively). The kinetics of the formation and excretion of salicylurate and the excretion of gentisate were similar to those found in previous studies.     

The use of methotrexate in rheumatoid arthritis

The use of methotrexate in rheumatoid arthritis is reviewed. Methotrexate, a folic acid antagonist, is sometimes employed in an attempt to symptomatically control patients whose disease does not respond adequately to conventional therapies. Systemic administration of 7.5-15 mg/wk in a "pulse" fashion appears to be effective without precipitating severe adverse effects. However, concern over potentially serious side effects and a lack of well-controlled clinical trials have limited its use to severe, refractory disease. Further studies are needed before its role in rheumatoid arthritis can justifiably be expanded.     

甲氨蝶呤及其活性代谢产物在类风湿关节炎患者体内的药动学模型研究

目的:通过模型化方法定量研究甲氨蝶呤(MTX)及其活性代谢产物(多谷氨酸结合物,MTXPGn)在类风湿关节炎(RA)患者血浆、红细胞及骨关节液的药动学特征.方法:使用Digiti-zer软件获取四篇文献中RA患者经口服、静脉、膝关节液注射三种方式给MTX后MTX及MTX-PGn在血浆、红细胞、骨关节液的时间-浓度数据,由ADAPT 5软件使用最大似然算法对这些数据同时进行非线性拟合分析,通过一个基于半生理特征的药动学模型获取MTX及MTXPGn在RA患者体内的血液和骨关节液中的药动学参数.结果:本文建立的PK模型可使用基本二房室模型较好描述血浆与关节液中MTX药动学特征,血浆与骨关节液中央室中的MTX可相互分布;可使用由血浆中央室以一级速率常数进入红细胞的五房室模型较好描述红细胞中MTXPG1-5的药动学特征,这五种物质之间可相互依次转化,并以相同速率常数被清除.其中的红细胞体积参数引用了健康人生理参数.上述估计的系统参数均接近于RA患者的生理、病理报告值,显示本模型估计值合理,并且除骨关节液中的分布清除率估计精密度略大于50％(56.7％)以外,其他参数均小于50％,显示参数估计可靠.结论:本文成功建立了MTX及MTXPGn在RA患者体内的基于半生理的药动学模型,该模型有助于定量理解MTX及MTXPGn在RA患者循环系统以及骨关节液药效部位之间的药动学特征.     

Naproxen pharmacokinetics in patients with rheumatoid arthritis during active polyarticular inflammation.

Patients with rheumatoid arthritis often have hypoalbuminaemia as a sign of disease activity. In view of the extensive binding of naproxen to albumin, the pharmacokinetics of total and unbound drug were studied in eight patients and eight healthy male volunteers during chronic intake of 500 mg twice daily. The area under the serum concentration-time curve of total naproxen during a dose interval, AUC (0,12), smaller in patients (641 +/- 101 mg l-1 h) than in volunteers (896 +/- 85 mg l-1 h; P less than 0.0001). The unbound naproxen AUCu (0,12) was larger in patients (1.9 +/- 0.9 mg l-1 h) than in volunteers (0.7 +/- 0.2 mg l-1 h; P less than 0.01). The higher unbound naproxen concentrations in patients were accompanied by an approximately 40% increase in apparent clearance/bioavailability (CL/F) and a 60% increase in volume of distribution (V/F). Both CL/F and V/F were inversely correlated with the individual serum albumin concentration (r = 0.76, P less than 0.001; r = -0.85, P less than 0.001, respectively). The high unbound naproxen concentration in the serum of patients with active rheumatoid arthritis and concomitant hypoalbuminaemia is not known to be accompanied by an increase in side effects and may be beneficial if anti-inflammatory effects correlate with unbound drug concentration.     

First dose and steady state pharmacokinetics of nimesulide and its 4-hydroxy metabolite in healthy volunteers.

The pharmacokinetics of nimesulide (4-nitro-2-phenoxymethane-sulfonanilide, NMS), a non-steroidal antiinflammatory drug, and of its 4-hydroxy metabolite (4-nitro-2-(4'-hydroxy-phenoxy)-methane sulfonanilide, OH-NMS) was studied after a single oral dose (200 mg) and after repeated treatments (100 mg every 12 hours for 7 days) of NMS to two groups of 12 healthy volunteers. Plasma concentrations of NMS and OH-NMS were followed for 48 hours after the single dose and up to the 12th hour on the 1st day and on the 7th day during repeated treatment. After the single dose of 200 mg peak plasma concentrations of the drug (9.85 micrograms/ml) were reached at 3.17 hours and the half-life during the elimination phase was 4.95 hours. The metabolite reached highest plasma levels (3.03 micrograms/ml) at 5.33 hours and its apparent half-life was similar to that of the parent drug (4.78 hours). NMS plasma levels on the 7th day, predicted from the results of the 1st day, were similar to the measured values. The pharmacokinetics of NMS or OH-NMS after single or repeated dose was not time or dose dependent.     

Highly aggressive plasmablastic neoplasms in patients with rheumatoid arthritis treated with methotrexate

Patients with rheumatoid arthritis occasionally develop lymphoproliferative disorders. Methotrexate-associated lymphoproliferative disorders is a lymphoproliferative disease or lymphoma in patients treated with methotrexate for autoimmune diseases, such as rheumatoid arthritis. Here we report two rare cases of highly aggressive plasmablastic lymphoproliferative disorders in rheumatoid arthritis treated with methotrexate.Case 1 is a 68-year-old female patient with leukemic transformation of malignant lymphoma. She received methotrexate therapy for rheumatoid arthritis for >6 years. The patient showed rapid progressive course and died on the 2nd hospital day. After the death, we diagnosed the patient as plasmablastic lymphoma. Case 2 is an 80-year-old female patient with plasmablastic plasma cell myeloma, with a history of methotrexate treatment for rheumatoid arthritis for >5 years. Although M-protein was decreased by chemotherapy, bone marrow examination revealed the further increase of plasmablastic cells and she died 2 months later.The present cases were difficult to diagnose because proliferation of malignant plasmablasts was hardly predicted because neither lymph node enlargement nor an evident M-protein was observed. Both cases showed aggressive features and extremely poor prognosis. Clinicians should be aware of the underlying malignant plasmablastic proliferation when inexplicable inflammatory findings are observed in inactive rheumatoid arthritis patients.