Pharmacokinetic Modeling of Morphine's Effect on Plasma Concentrations of Ticagrelor and Its Metabolite in Healthy Volunteers

This study aimed to build a mathematical model describing the pharmacokinetics of ticagrelor and its active metabolite (AR-C124910XX) in a stable setting with concomitant administration of morphine. The model consists of a set of four differential equations prepared upon the available knowledge regarding the biological processes in the pharmacokinetics of ticagrelor. The set of equations was solved numerically using the Runge–Kutta method. The data were obtained in a double-blind, randomized, placebo-controlled, crossover trial. Twenty-four healthy volunteers received a 180-mg ticagrelor loading dose together with either 5-mg morphine or placebo. Blood samples were analyzed with liquid chromatography–tandem mass spectrometry to assess plasma concentrations of ticagrelor and AR-C124910XX before ticagrelor loading dose and after that 1, 2, 3, 4, and 6 h. The model allowed us to reproduce the experimental results accurately and led us to conclusions consistent with clinical observations that morphine delays the time of maximum drug concentration and that the morphine effect occurs due to decreased gastrointestinal motility. Based on the model, we were able to predict the effect of drug dose on receptor blocking efficacy.

Acute Limb Ischemia after Intake of the Phenylethylamine Derivate NBOMe

Objective: N-(2-methoxy) benzyl-phenethylamine (NBOMe) derivatives have a high affinity to the serotonin receptor 2A and emerged as new psychedelic agents. We report the case of a 30-year-old man admitted to the hospital because of acute ischemia of the left arm with clinical symptoms of pallor, pulselessness, paresthesia, and a motoric deficit. The patient had a history of schizophrenia and drug abuse and disclosed during the hospital stay the sublingual intake of a substance bought as 25I-NBOMe the night before the ischemic event. Methods: Routine clinical diagnostics including among others color-coded duplex sonography and computed tomography angiography (CTA) were performed. The remainder of the drugs was analyzed using high performance liquid chromatography. Results: Initial color-coded duplex sonography of the upper left limb showed pathological flow profiles of the axillary, brachial, ulnar, and radial artery with a reduced diameter of the ulnar (0.9 mm) and radial (1.1 mm) artery. In consequence, peripheral vasospasm, distal arterial thrombosis, or arterial embolization was anticipated. As therapeutic measures, the patient immediately received intravenous systemic vasodilators (alprostadil) and therapeutic anticoagulation with low molecular weight heparin. Instant symptom improvement was observed within the first day after therapy initiation. The subsequently performed CTA of the heart and left arm showed no signs of thrombotic material. Treatment was continued for five days and the patient was released thereafter having completely normalized perfusion in his left arm. Outpatient treatment was continued with calcium-channel blockers, as the patient had also displayed arterial hypertension. Drug analysis retrieved a composition of the isomers 25I-NBOMe, 25C-NBOMe, and 25H-NBOMe as well as traces of pentylon. Conclusion: NBOMe ingestion implicates the risk of peripheral vasospasms with severe, limb-threatening ischemia.

Morphine Interaction with Aspirin: a Double-Blind, Crossover Trial in Healthy Volunteers

Aspirin is a cornerstone in the antiplatelet therapy for acute coronary syndromes. Coadministration of morphine may potentially influence the intestinal absorption, pharmacokinetics, and pharmacodynamics, as seen with P2Y₁₂ inhibitors. In this trial, healthy volunteers were randomized to receive morphine (5 mg, i.v. bolus injection) at one of seven different time points before, after, or with aspirin (162 mg, p.o.) in a double-blind, placebo-controlled fashion. After a 14-day washout, subjects received placebo instead of morphine. Pharmacokinetics were determined by liquid chromatography, and aspirin's effects were measured by platelet function tests (whole-blood platelet aggregation: multiplate, platelet plug formation: PFA-100). Morphine increased the total acetylsalicylic acid exposure by 20% compared with placebo when given simultaneously with aspirin, whereas C_max and t_max were not altered. Morphine had no significant effect on aspirin-induced platelet inhibition. In contrast to coadministration with P2Y₁₂ inhibitors, morphine appears to have negligible interaction with aspirin.

Clopidogrel in Critically Ill Patients

Only limited data are available regarding the treatment of critically ill patients with clopidogrel. This trial investigated the effects and the drug concentrations of the cytochrome P450 (CYP450) activated prodrug clopidogrel (n = 43) and the half‐life of the similarly metabolized pantoprazole (n = 16) in critically ill patients. ADP‐induced aggregometry in whole blood classified 74% (95% confidence intervals 59–87%) of critically ill patients as poor responders (n = 43), and 65% (49–79%) responded poorly according to the vasodilator‐stimulated phosphoprotein phosphorylation (VASP‐P) assay. Although the plasma levels of clopidogrel active metabolite normally exceed the inactive prodrug ∼30‐fold, the parent drug levels even exceeded those of the metabolite 2‐fold in critically ill patients. The half‐life of pantoprazole was several‐fold longer in these patients compared with reference populations. The inverse ratio of prodrug/active metabolite indicates insufficient metabolization of clopidogrel, which is independently confirmed by the ∼5‐fold increase in half‐life of pantoprazole. Thus, high‐risk patients may benefit from treatment with alternative platelet inhibitors.

Prasugrel in critically ill patients

While prasugrel is indicated for the treatment of myocardial infarction, its effects in the most severely affected patients requiring intensive care is unknown, so that we measured the antiplatelet effects and sparse pharmacokinetics of prasugrel in critically ill patients. Twenty-three patients admitted to medical intensive care units, who were treated with 10 mg prasugrel once daily, were included in this prospective trial. Critically ill patients responded poorly to daily prasugrel treatment: adenosine diphosphate (ADP)-induced aggregation in whole blood classified 65 % (95 % confidence intervals (CI) 43-84 %) of patients as having high on treatment platelet reactivity, platelet function under high shear rates even 74 % (95 %CI 52-90 %). There was only limited additional inhibition provided 2 hours after the next dose of prasugrel. In contrast, insufficient inhibition of the target was only seen in 26 % (95 %CI 10-48 %) of patients as measured by the vasodilator-stimulated phosphoprotein phosphorylation (VASP-P) assay. Low effective plasma levels of prasugrel active metabolite were measured at trough [0.5 (quartiles 0.5-1.1) ng/ml at baseline], and 2 hours after intake [5.7 (3.8-9.8) ng/ml], but showed coefficients of variation of ~70 %. In sum, inhibition of platelet aggregation by prasugrel is not uniform but highly variable in critically ill patients, similar to clopidogrel in a general population. The pharmacokinetic measurements indicate that poor absorption/metabolism of prasugrel may partly contribute while inflammation induced heightened intrinsic platelet reactivity may also play a role.

Acetylsalicylic acid in critically ill patients: a cross-sectional and a randomized trial

BACKGROUND

Despite decades of clinical use, the pharmacokinetics and the effects of acetylsalicylic acid (ASA) in critically ill patients remain ill-defined. We aimed to investigate the pharmacokinetics and the effects of different ASA formulations during critical illness.

DESIGN

A cross-sectional study and a randomized, parallel-group trial were performed. Critically ill patients under chronic oral ASA treatment (100 mg enteric-coated) were screened for high 'on-treatment' platelet reactivity (HTPR) according to arachidonic acid-induced whole-blood aggregometry. Thirty patients with HTPR were randomized to receive 100 mg ASA intravenously, 100 mg enteric-coated ASA bid (bis in die) or 81 mg chewable ASA (n = 10 per group). Serum thromboxane B2 (TXB2) levels, ASA and salicylic acid levels were quantified.

RESULTS

Of 66 patients, 85% (95% confidence intervals 74-93%) had HTPR. Compared to baseline infusion of 100 mg, ASA significantly reduced platelet aggregation after 24 h to median 80% (Quartiles: 66-84%). Intake of 81 mg chewable ASA significantly reduced platelet aggregation to 75% (54-86%) after four hours, but increased it to 117% after 24 h (81-163%). Treatment with 100 mg enteric-coated ASA bid decreased platelet aggregation after 24 h to median 56% (52-113%). Baseline TXB2 levels were median 0·35 ng/mL (0·07-0·94). Infusion of ASA or intake of 100 mg ASA bid reduced TXB2 levels to 0·07-0·18 ng/mL after 24 h, respectively. Chewable ASA reduced TXB2 levels only transiently. Pharmacokinetic analysis revealed highly variable absorption patterns of oral ASA formulations.

CONCLUSION

There is a very high prevalence of HTPR in critically ill patients on peroral ASA therapy, caused by an incomplete suppression of TXB2 and/or by impaired absorption of ASA.

Abciximab as a bridging strategy to overcome morphine-prasugrel interaction in STEMI patients

OBJECTIVE

The present study investigated whether the glycoprotein (GP)IIb/IIIa receptor blocker abciximab might be a successful bridging strategy to achieve adequate levels of platelet inhibition rapidly in cases where prasugrel is used in morphine-pretreated ST-elevation myocardial infarction (STEMI) patients.

METHODS

In a prospective observational cohort study, 32 patients presenting with STEMI were given prasugrel at a loading dose of 60 mg. Patients were stratified into four groups, according to morphine and/or abciximab use. Adenosine diphosphate (ADP)-induced platelet aggregation was measured at four time points: at baseline, and at 2 h, 1 day and 2 days after prasugrel loading.

RESULTS

Morphine use was associated with a three-fold higher level of ADP-induced platelet aggregation 2 h after prasugrel loading compared with no morphine/no abciximab (P = 0.019). However, when abciximab was infused in the catheterization laboratory, the effect of morphine on ADP-induced platelet aggregation disappeared (P = 0.884). This interaction was also seen in the presence of high on-treatment platelet reactivity (HTPR) at 2 h; while HTPR was seen in 88% of morphine users/no abciximab users, it was found in only 17-20% in the three other groups (P = 0.003). The effect of morphine disappeared by day 1 - 2.

CONCLUSION

The infusion of the GPIIb/IIIa receptor blocker abciximab allows immediate and efficient platelet inhibition in STEMI patients concomitantly receiving the oral ADP receptor blocker prasugrel and morphine.

Procoagulant microparticles promote coagulation in a factor XI-dependent manner in human endotoxemia

Essentials The procoagulant effects of microparticles (MPs) on coagulation in endotoxemia are not known. MPs from endotoxemia volunteers were evaluated for procoagulant activity in a plasma milieu. MPs from endotoxemia volunteers shortened clotting times and enhanced thrombin generation. MP procoagulant effects were mediated in a factor XI-dependent manner.

SUMMARY

Background Human endotoxemia is characterized by acute inflammation and activation of coagulation, as well as increased numbers of circulating microparticles (MPs). Whether these MPs directly promote coagulation and through which pathway their actions are mediated, however, has not been fully explored. Objectives In this study, we aimed to further characterize endotoxin-induced MPs and their procoagulant properties using several approaches. Methods Enumeration and characterization of MPs were performed using a new-generation flow cytometer. Relative contributions of the extrinsic and intrinsic pathways in MP-mediated procoagulant activity were assessed using plasmas deficient in factor (F) VII or FXI or with blocking antibodies to tissue factor (TF) or FXIa. Results Total MPs and platelet MPs were significantly elevated in plasma at 6 h after infusion of endotoxin in healthy human subjects. MPs isolated from plasma following endotoxin infusion also demonstrated increased TF activity in a reconstituted buffer system. When added to recalcified platelet-poor plasma, these MPs also promoted coagulation, as judged by a decreased clotting time with shortening of the lag time and time to peak thrombin using calibrated automated thrombography (CAT). However, the use of FVII-deficient plasma or blocking antibody to TF did not inhibit these procoagulant effects. In contrast, plasma clotting time was prolonged in FXI-deficient plasma and a blocking antibody to FXIa inhibited all MP-mediated parameters in the CAT assay. Conclusions The initiation of coagulation by cellular TF in endotoxemia is in contrast to (and presumably complemented by) the intrinsic pathway-mediated procoagulant effects of circulating MPs.

Morphine decreases ticagrelor concentrations but not its antiplatelet effects: a randomized trial in healthy volunteers

BACKGROUND

Our recent drug interaction trial with clopidogrel shows that morphine decreases the concentrations and pharmacodynamic effects of clopidogrel, which could lead to treatment failure in susceptible individuals. We hypothesized that the pharmacodynamic consequences of drug-drug interactions would be less between morphine and ticagrelor.

MATERIALS AND METHODS

Twenty-four healthy subjects received a loading dose of 180 mg ticagrelor together with placebo or 5 mg morphine intravenously in a randomized, double-blind, placebo-controlled, crossover trial. Pharmacokinetics were determined by liquid chromatography tandem mass spectrometry, and ticagrelor pharmacodynamic effects were measured by platelet function tests (whole blood platelet aggregation: multiplate, platelet plug formation: PFA-100, vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay).

RESULTS

Concomitant i.v. injection of morphine slows drug resorption of ticagrelor and its active metabolite (P < 0·05) by 1 h and decreases plasma levels of ticagrelor and its active metabolite by 25-31% (P ≤ 0·03) and the drug exposure (area under the curve) by 22-23% (P ≤ 0·01). Importantly, however, the pharmacodynamic effects of ticagrelor on platelet aggregation in whole blood, platelet plug formation and VASP phosphorylation are not affected by morphine.

CONCLUSIONS

Morphine co-administration moderately decreases ticagrelor plasma concentrations but does not inhibit its pharmacodynamic effects in healthy volunteers within 6 h after drug administration. Limitations of our trial include the investigation in healthy volunteers under standardized conditions, which does not necessarily reflect a realistic emergency scenario.

Absorption kinetics of low-dose chewable aspirin--implications for acute coronary syndromes

BACKGROUND

This study describes the implications of the pharmacokinetics of low-dose chewable aspirin for acute coronary syndromes. Current guidelines recommend the administration of 162-325 mg aspirin chewing tablets for the treatment of acute myocardial infarction. Although aspirin is widely used and a cornerstone in myocardial infarction, there is no information available on the pharmacokinetics of low doses of chewable aspirin.

MATERIALS AND METHODS

This prospective trial assessed the pharmacokinetics of acetylsalicylic acid and its metabolite salicylic acid after intake of 162 mg chewable low-dose aspirin in 35 healthy volunteers. Plasma drug and metabolite levels were analysed using high-performance liquid chromatography, and corresponding pharmacodynamics were determined by impedance aggregometry.

RESULTS

Acetylsalicylic acid was rapidly absorbed with a mean Tmax of 27 ± 8 min. Tmax of salicylic acid was 69 ± 21 min. Mean Cmax was 1·8 ± 0·6 mg/L and 7·6 ± 1·4 for acetylsalicylic acid and salicylic acid, respectively. Arachidonic acid-induced aggregation showed maximum platelet inhibition 30 min after drug ingestion.

CONCLUSIONS

The characterization of the plasma-time profile fills the gap between the lack of data on pharmacokinetics and the pharmacodynamics and the recommendation for using low-dose chewable aspirin for acute coronary syndromes. We describe for the first time that a 162-mg dose of chewable aspirin is rapidly absorbed and achieves plasma concentrations of the active metabolite salicylic acid required to maximally inhibit platelet aggregation. However, a 162-mg dose is truly a minimum, and doubling this dose might be better for patients with myocardial infarction.

Decreased renal function in hypertensive emergencies

Data about acute renal function in hypertensive crises are scarce. We hypothesised that acute kidney damage could result from hypertensive emergency (HE), as indicated by the earliest biomarker of kidney injury, neutrophil gelatinase-associated lipocalin (NGAL). Thus, we compared renal function between patients with HE, patients with urgencies and normotensive controls. Sixty emergency department patients were enroled in a prospective, cross-sectional study. Creatinine, blood urea nitrogen (BUN), NGAL and cystatin C were measured and estimated glomerular filtration rate was calculated (eGFR). Creatinine and BUN were significantly higher and eGFR was significantly lower in HE as compared with urgencies or controls (P < 0.01). Similarly, cystatin C and NGAL levels were significantly higher in emergencies compared with the other groups (P < 0.001). All renal function parameters were similar between urgencies and controls. Among HE, NGAL was significantly higher (61%) in patients with pulmonary oedema than in those with cerebral events (P = 0.008), whereas the other parameters were not significantly different. In conclusion, this cross-sectional investigation showed that markers of acute and chronic kidney injury were higher in patients with HE than in urgencies or controls. These results should encourage further studies to better characterise the role of acute kidney damage in hypertensive pulmonary oedema, and HE in general.

Reversal strategy in antagonizing the P2Y12 -inhibitor ticagrelor

BACKGROUND

Patients on antiplatelet therapy have a higher incidence of bleeding complications. Reversal of antiplatelet drug effects is an important issue at trauma or emergency departments. For old and conventional anticoagulants, reversal strategies are established. While the effects of ticagrelor are reversible, developing a method to restore platelet function in patients is of importance due to its longer half-life (approximately 8 h), compared with other P2Y12 -inhibitors.

MATERIALS AND METHODS

We report an ex vivo model to reverse the effects of the novel and highly effective P2Y12 -inhibitor ticagrelor in 20 healthy volunteers. To normalize platelet reactivity, we added increasing amounts of autologous platelet-rich plasma (PRP) to whole blood which was obtained 3 h after the intake of 180 mg of ticagrelor. Platelet aggregation was assessed by whole blood multiple electrode aggregometry (MEA), which is based on impedance aggregometry.

RESULTS

The basal ADP-induced platelet aggregation averaged 71 ± 16 U (Units). Ticagrelor decreased ADP-induced platelet aggregation to 16 ± 8 U. A clear dose-response was obtained after spiking whole blood with increasing amounts of PRP. It is estimated that ≥2 units of apheresis platelet concentrates will be necessary to completely restore baseline platelet aggregation in the majority of patients after ticagrelor.

CONCLUSIONS

Platelets dose dependently improve ex vivo platelet aggregation of subjects after a loading dose of 180 mg of ticagrelor, making transfusion of platelet concentrates potentially useful in bleeding patients and those who need to undergo emergency surgery.

Comparison of a new ELISA-based with the flow cytometric assay for vasodilator-associated stimulated phosphoprotein (VASP) phosphorylation to assess P2Y12 -inhibition after ticagrelor intake

BACKGROUND

Ticagrelor is a P2Y12 receptor antagonist, with superior effects but also ensuing enhanced bleeding risk as compared to clopidogrel. Determination of platelet inhibition may be useful to confirm efficient platelet inhibition on an individual patient level and to identify patients at risk for bleeding. The vasodilator-associated stimulated phosphoprotein (VASP) phosphorylation assay specifically measures platelet P2Y12 inhibition, but has so far required individual sample processing. A new ELISA-based VASP assay has been developed which allows batch analysis after initial platelet activation. Due to the reversible binding of ticagrelor it is unclear if the ELISA and flow cytometric assays provide comparable results; several washing steps of the ELISA may potentially result in false low results through dilution.

METHODS

We hypothesized that the conventional and new methods may be comparable when ticagrelor is used. We pair-wise compared the platelet reactivity index (PRI) between assays in a prospective clinical trial. Six healthy volunteers received a single 180 mg loading dose of ticagrelor.

RESULTS

PRI-values of the two methods correlated well (r=0.97, p<0.001). Ticagrelor rapidly decreased PRI values on average after 50 minutes, but nadir levels 2-6 hours after ticagrelor intake were 15% higher when PRI% was measured with the flow cytometric method. Bland-Altman analysis showed that the flow cytometric assay measured markedly higher PRI levels than the new ELISA-based technique (mean difference 13%).

CONCLUSIONS

The new ELISA-based VASP assay offers an alternative to the currently used flow cytometric method, but measures lower PRI levels, particularly when PRI falls below 20% after ticagrelor intake. © 2013 Clinical Cytometry Society.

A randomized, double-blind, parallel, single-site pilot trial to compare two different starting doses of methotrexate in methotrexate-naïve adult patients with rheumatoid arthritis

BACKGROUND

Methotrexate (MTX) is a cornerstone in the treatment of rheumatoid arthritis. Despite its widespread use, expert opinions differ about the optimal MTX starting dosage to achieve rapid onset of action while averting increased occurrence of adverse effects. Plasma concentrations have not been assessed in previous studies that monitored clinical efficacy.

OBJECTIVE

This study was performed to compare the pharmacokinetic parameters and clinical response of a standard (15 mg) and an accelerated (25 mg) dosing regimen, each administered orally once a week.

METHODS

This randomized, controlled, double-blind, parallel, single-site study included 19 MTX-naïve patients older than 18 years with rheumatoid arthritis. Patients participated for 16 weeks. Disease activity was assessed using the Disease Activity Score in 28 joints (DAS-28) as the primary outcome parameter. Plasma MTX concentrations were measured using HPLC at weeks 1, 5, 10, and 16. Tolerability was assessed via routine blood analysis (hematology and clinical chemistry) and a patient questionnaire to monitor adverse events. Reported or observed adverse events were recorded along with information about their severity and causal relationship to the study medication.

RESULTS

Nineteen white patients (13 women and 6 men; mean age, 56 years; and mean weight, 74 kg) participated. At study entry, mean (SD) DAS-28-4v (erythrocyte sedimentation rate) was 4.73 (1.02). Health Assessment Questionnaire scores were 1.45 (0.85); for C-reactive protein, 11.45 (10.04) mg/dL; for alkaline phosphatase, 73.58 (19.91) U/L; for aspartate aminotransferase, 23.32 (7.13) U/L; and for creatinine, 0.87 (0.22) mg/dL. Although pharmacokinetic parameters such as AUC and C(max) were significantly higher after the accelerated dosing regimen, clinical activity scores (DAS-28) and inflammation parameters (C-reactive protein) did not indicate a significant benefit of an accelerated starting regimen. Considering toxicity, no elevation in liver function enzymes and no decrease in renal function were observed using the accelerated dosing (statistical significance set at P ≤ 0.05). No serious adverse events were noted. All observed adverse events were classified as study related. Overall, adverse events were noted in 58% of patients. Comparison of the two doses revealed that 60% of patients receiving the standard dosing regimen and 56% of patients receiving the accelerated dosing regimen reported adverse events, the most frequent being gastrointestinal. These events were generally self-limiting.

CONCLUSIONS

Differences in clinical response between these two small selected patient groups who received an initial oral dose of either 15 or 25 mg MTX per week did not reach the level of statistical significance. The overall incidence of adverse effects, all classified as study related, was 58%, with 60% of patients receiving the standard dosage and 56% of patients receiving the accelerated dosing regimen reporting adverse effects. However, because of the small sample size, this study was not powered to detect differences in the incidence of adverse events between the two dosing groups. ClinicalTrials.gov identifier: NCT00695188.

A short-chain methotrexate polyglutamate as outcome parameter in rheumatoid arthritis patients receiving methotrexate

OBJECTIVES

Methotrexate (MTX) is a cornerstone in the treatment of rheumatoid arthritis (RA). Although in general MTX is very effective, the major drawback is the large inter-patient variability in clinical response. The circulating levels of MTX polyglutamates (MTXPGs) are supposed to correlate with clinical efficacy, therefore having a potential role in drug monitoring. However, there is a controversial discussion about the importance of methotrexate polyglutamates as outcome parameters in the therapy of rheumatoid arthritis. The aim of the present study was to investigate the formation and pharmacokinetics of MTXPGs and to correlate their concentration with clinical response in MTX-naïve patients.

METHODS

The pharmacokinetics of erythrocyte MTXPGs was determined in samples of nineteen MTX-naïve patients by high pressure liquid chromatography (HPLC) using post-column photo-oxidation and fluorimetric detection. The relationship between erythrocyte concentrations of MTXPGs and the primary outcome parameter DAS-28 was assessed using the Spearman's correlation coefficient.

RESULTS

The short-chain polyglutamate MTXPG2 revealed to be a potential marker for clinical outcome in rheumatoid arthritis with a statistically significant positive correlation of MTXPG2 Cmax levels and improvement in DAS-28 (+0.518, p=0.023) over 16 weeks. Furthermore, Cmax levels of MTXPG2 negatively correlated with basophils (-0.478, p=0.038) and eosinophils (-0.531, p=0.019), both pro-inflammatory cells involved in the disease.

CONCLUSIONS

MTXPG2 seems to be a potential indicator for clinical response and may serve as a marker for drug monitoring.

The influence of methotrexate on the gene expression of the pro-inflammatory cytokine IL-12A in the therapy of rheumatoid arthritis

OBJECTIVES

Methotrexate (MTX) is a cornerstone in the treatment of rheumatoid arthritis (RA). Among its anti-proliferative activity, the anti-inflammatory mechanisms of MTX seem to play a major role in the treatment of RA. MTX reduces the production of pro-inflammatory cytokines such as interleukin (IL)-1, IL-2, IL-6 and interferon (INF)-γ, while the gene expression of anti-inflammatory Th2 cytokines like IL-4 and IL-10 is increased - altogether resulting in the anti-inflammatory effect. As little is known about the impact of MTX on other cytokines involved in the pathogenesis of RA, the present trial investigated the effect of MTX on IL-12A and IL-18 gene expression by peripheral blood mononuclear cells (PBMCs). For comparison, the effect on IL-6 and tumour necrosis factor (TNF) was analysed.

METHODS

Using real-time PCR, mRNA concentrations of pro-inflammatory cytokines were determined in PBMCs from 17 patients before and during MTX therapy. Furthermore, gene expression was correlated with clinical and pharmacokinetic parameters such as methotrexate polyglutamate concentrations (Spearman's correlation coefficient). To eliminate concomitant corticosteroids as confounding factor, a subgroup analysis for methotrexate without corticosteroids was performed in 6 patients.

RESULTS

MTX statistically significantly reduced the mRNA expression of IL-12A by PBMCs in rheumatoid arthritis patients (Wilcoxon-test for paired samples, p<0.046). Consistent with other reports, IL-6 was reduced under MTX treatment. Although the combination of MTX and corticosteroids significantly reduced the gene expression of IL-18, this key molecule was unaffected by MTX without corticosteroids. Our results were further supported by a negative correlation of methotrexate polyglutamate concentrations and the mRNA expression of the pro-inflammatory cytokines IL-6 and IL-12A.

CONCLUSIONS

We describe a novel effect of MTX reducing the gene expression of IL-12A independently of corticosteroid application in patients. This impact was further enhanced by a reduction of IL-12A-producing lymphocytes and neutrophils under MTX treatment. These results expand the understanding of the mechanism of action of the most widely used drug in RA.