J. Dehais

Clinical Pharmacokinetics of Low-Dose Pulse Methotrexate in Rheumatoid Arthritis

SummaryLow-dose pulse methotrexate has emerged as one of the most frequently used slow-acting, symptom-modifying antirheumatic drugs in patients with rheumatoid arthritis (RA) because of its favourable risk-benefit profile.Methotrexate is a weak bicarboxylic acid structurally related to folic acid. The most widely used methods for the analysis of methotrexate are immunoassays, particularly fluorescence polarisation immunoassay. After oral administration, the drug is rapidly but incompletely absorbed. Since food does not significantly affect the bioavailability of oral methotrexate in adult patients, the drug may be taken regardless of meals. There is a marked interindividual variability in the extent of absorption of oral methotrexate. Conversely, the intraindividual variability is moderate even over a long time period. Intramuscular and subcutaneous injections of methotrexate result in comparable pharmacokinetics, suggesting that these routes of administration are interchangeable.A mean protein binding to serum albumin of 42 to 57% is usually reported. Again, the unbound fraction exhibits a large interindividual variability. The steady-state volume of distribution is approximately 1 L/kg. Methotrexate distributes to extravascular compartments, including synovial fluid, and to different tissues, especially kidney, liver and joint tissues. Finally, the drug is transported into cells, mainly by a carrier-mediated active transport process.Methotrexate is partly oxidised by hepatic aldehyde oxidase to 7-hydroxy-methotrexate. This main, circulating metabolite is over 90% bound to serum albumin. Both methotrexate and 7-hydroxy-methotrexate may be converted to polyglutamyl derivatives which are selectively retained in cells. Methotrexate is mainly excreted by the kidney as intact drug regardless of the route of administration. The drug is filtered by the glomeruli, and then undergoes both secretion and reabsorption processes within the tubule. These processes are differentially saturable, resulting in possible nonlinear elimination pharmacokinetics. The usually reported mean values for the elimination half-life and the total body clearance of methotrexate are 5 to 8 hours and 4.8 to 7.8 L/h, respectively. A positive correlation between methotrexate clearance and creatinine clearance has been found by some authors.Finally, the pharmacokinetics of low-dose methotrexate appears to be highly variable and largely unpredictable even in patients with normal renal and hepatic function. Furthermore, studies in patients with juvenile rheumatoid arthritis provide evidence of age-dependent pharmacokinetics of the drug. These features must be considered when judging the individual clinical response to methotrexate therapy.Various drugs currently used in RA may interact with methotrexate. Aspirin might affect methotrexate disposition to a greater extent than other nonsteroidal anti-inflammatory drugs without causing greater toxicity. Corticosteroids do not interfere with the pharmacokinetics of methotrexate, whereas chloroquine may reduce the gastrointestinal absorption of the drug. Folates, especially folic acid, have been shown to reduce the adverse effects of methotrexate without compromising its efficacy in RA. Finally, both trimethoprim-sulfamethoxazole (cotrimoxazole) and probenecid lead to increased toxicity of methotrexate, and hence should be avoided in patients receiving these drugs.A relationship between oral dosage and efficacy has been found in the range 5 to 20mg methotrexate weekly. The plateau of efficacy is attained at approximately 10 mg/m2/week in most patients. No clear relationship between pharmacokinetic parameters and clinical response has been demonstrated. Overall, the dosage must be individualised because of interindividual variability in the dose-response curve. This variability is probably related, at least in part, to the wide interindividual variability in the disposition of the drug.

Propionibacterium acnes isolated from synovial tissue and fluid in a patient with oligoarthritis associated with acne and pustulosis

This report describes the case of a patient with a 14-month course of severe oligoarthritis associated with acne. Pure cultures of Propionibacterium acnes were isolated from synovial tissue and synovial fluid specimens collected from the same joint after a 4-month interval. After 2 months of treatment with roxithromycin 300 mg/day, rifampicin 1,200 mg/day, and a nonsteroidal antiinflammatory drug (NSAID), followed by 4 months of treatment with azithromycin 1 gm/week and an NSAID, the synovitis persisted. Cultures of skin lesions and synovial fluid at this time were negative. Although P acnes has previously been isolated from bone specimens obtained from patients with osteitis associated with acne, this is the first report of the isolation of this microorganism from the synovial tissue of a patient with arthritis associated with acne. Our findings raise the question of the role of P acnes in the pathogenesis of arthritis associated with acne.

Central analgesic effects of aspirin-like drugs

Summary— Aspirin‐like drugs mainly include paracetamol, salicylates and other non‐steroidal anti‐inflammatory drugs, and metamizole. Their analgesic effect is classically ascribed to a peripheral site of action, within the pain‐processing site. There is, however, convincing evidence that a central component contributes to the overall analgesia provided by these agents. Experimental and clinical studies referring to this challenging proposal are reviewed here. The exact site and mode of action of aspirin‐like drugs within the central nervous system remains controversial. It is likely that supraspinal mechanisms play an important role. Some experiments lend support to the involvement of monoaminergic control systems. Other data indicate that these drugs act centrally through the inhibition of cyclo‐oxygenase activity. The interactions between prostaglandins and various neurotransmitters suggest that both mechanisms may be linked.

Myeloid dendritic cells correlate with clinical response whereas plasmacytoid dendritic cells impact autoantibody development in rheumatoid arthritis patients treated with infliximab

IntroductionThe objective of our study was to identify the significance of the subtypes of dendritic cell (DC), specifically myeloid DCs (mDCs) and plasmacytoid DCs (pDCs), in rheumatoid arthritis (RA) pathogenesis through their longitudinal follow-up in patients receiving infliximab.MethodsCirculating mDC and pDC levels were evaluated by flow cytometry in RA patients (n = 61) and healthy volunteers (n = 30). In RA patients, these levels were measured before and during infliximab therapy. Their counts were correlated to RA disease activity markers and anti-nuclear antibody occurrence. IFNα production was measured by ELISA in serum of RA patients and, in vitro, in supernatant of peripheral blood mononuclear cells stimulated by influenza virus in the presence or absence of infliximab. Statistical evaluations were based on Mann–Whitney tests or Wilcoxons signed-rank tests.ResultsRA patients with active disease were characterized by a baseline decrease in both circulating pDCs and mDCs. Disease activity markers inversely correlated only with mDC level. This level increased in RA patients responsive to infliximab therapy, to reach the level observed in controls. Conversely, anti-nuclear antibody appearance during infliximab therapy correlated inversely with pDC level and was associated with increased serum IFNα level and circulating plasma cells number. In vitro studies revealed that infliximab kept pDCs in an IFNα secreting state upon viral stimulation allowing differentiation of B cells into anti-nuclear antibody-secreting plasma cells.ConclusionsThis study reveals two distinct roles for pDC and mDC in RA. Circulating mDCs mainly contribute to RA activity, whereas pDCs seem to be involved in appearance of anti-nuclear antibodies under infliximab therapy through the ability of this drug to keep pDCs in an IFNα secreting state.

Arthropathy associated with anti-Jo-1 antibody

Anti-Jo-1 antibody is associated with an overlap syndrome usually described as the association of idiopathic inflammatory myopathy, pulmonary fibrosis and polyarthritis. We report three observations illustrating different aspects of arthropathy associated with anti-Jo-1 antibody. Two patients presented with a deforming and erosive arthritis affecting the hands, periarticular calcifications and dislocation of the interphalangeal (IP) joint of the thumb. The third patient, who had a short disease course, presented only with a mild non-erosive polyarthritis of both hands, metacarpophalangeal joint narrowing and periarticular calcifications. All the patients had interstitial pulmonary syndrome. Only two of them had myositis. An arthropathy characterized by erosive arthritis of the fingers, with dislocation of the IP joint of the thumb and periarticular calcifications, seems to be specifically associated with anti-Jo-1 antibody.

Cholesterol crystal embolization simulating focal myositis

Cholesterol crystal embolization usually produces characteristic skin lesions. We report a case responsible for myositis of the calf without suggestive skin lesions. The outcome in this 58-year-old patient was spontaneously favorable. Cholesterol crystal embolization can produce a range of clinical symptoms, with the skin, kidneys, and eyes being the most common targets. Generalized forms can result in systemic disease. The diagnosis rests on histological findings, and the treatment is symptomatic. Anticoagulants have been shown to worsen the manifestations, whereas antiplatelet therapy may be useful.

Manifestations articulaires associées à la présence de l’anticorps anti-Jo-1

Resume L’anticorps anti-Jo-1 est associe a un syndrome de chevauchement caracterise par l’association d’une fibrose pulmonaire, d’une myopathie inflammatoire idiopathique et d’une polyarthrite. Nous rapportons trois observations illustrant differents aspects des manifestations articulaires associees a la presence de l’anticorps anti-Jo-1. Deux patientes avaient une polyarthrite erosive et deformante des mains associee a des calcifications periarticulaires et a une luxation de l’interphalangienne du pouce. La troisieme patiente, pour qui le recul est moins important, avait simplement une polyarthrite non erosive des mains associee a des calcifications periarticulaires. Les trois patientes avaient une fibrose pulmonaire et seulement deux une atteinte musculaire. Une arthropathie caracterisee par une arthrite erosive des doigts, avec une dislocation de l’interphalangienne du pouce et des calcifications periarticulaires semble etre specifiquement associee a la presence de l’anticorps anti-Jo-1.

Emboles de cristaux de cholestérol simulant une myosite focale

Resume Les manifestations thrombotiques liees aux emboles de cristaux de cholesterol sont habituellement accompagnees de signes cutanes. Nous rapportons l’observation d’une myosite isolee du mollet chez un homme de 58 ans, originale par l’absence de manifestations dermatologiques specifiques. Le bilan etiologique s’est avere negatif. L’evolution etait spontanement favorable. Les signes cliniques des emboles de cristaux de cholesterol sont polymorphes. Classiquement, les atteintes cutanees, renales et ophtalmologiques figurent au premier plan. Des formes generalisees peuvent en imposer pour une pathologie systemique. Le diagnostic est histologique. La therapeutique est symptomatique, les anti-agregants plaquettaires sont discutes. Neanmoins le role aggravant des therapeutiques anticoagulantes est reconnu.