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About
Gout, secondary to sodium urate crystal deposition, is responsible of recurrent inflammatory painful flares. Efficacy of colchicine which is the first line drug for the treatment and prophylaxis of gout flare varies and only half of treated patients experience good response. This study aims to optimize colchicine prescription for the treatment and prophylaxis of gout flare.
Current data suggest that efficiency of colchicine relies on its maximum blood concentration (Cmax).
In this study, the investigators hypothesize that responders to colchicine treatment have higher colchicine Cmax than non-responder patients following the recommended dose regimen (1 mg then 0.5 mg 1 hour later).
The individual pharmacokinetics (PK) of colchicine remains poorly investigated while the assessment of individual drug metabolisms can be performed.
The hypothesis of this study stands that several factors contribute to the variability of colchicine Cmax. The analysis of individual PK profile and a well-characterized metabolism of colchicine will permit a personalized treatment regimen for the treatment and prophylaxis of gout flares.
Full description
Gout flare is driven by interleukin (IL)-1β production and can be treated by colchicine, NSAID, corticoid or IL-1β blockers (PMID 27457514).
Colchicine is an alkaloid compound that disrupts cytoskeletal functions through inhibition of microtubule polymerization and consequently interferes with the intracellular assembly of the inflammasome NLRP3 complex that mediates activation of IL-1β (PMID 16407889).
Efficacy of colchicine treatment in gout flare varies between 37.5 and 64% (PMID 3314832; 20131255). Previous study suggests that colchicine efficiency relies on its blood maximum concentration (Cmax) (PMID 20131255). However this hypothesis needs to be confirmed.
The hypothesis of this study stands that colchicine Cmax varies with individual colchicine pharmacokinetics and that this individual variation may explain the variation response of colchicine treatment.
Absorption of orally administrated colchicine varies between 24 et 88% with an average of 45%. Thus, following oral administration of 1.8 mg colchicine over 1 hour to healthy young adults, under fasting condition, the colchicine Cmax (mean 6.2 ng/ml) is reached within a median of 1.8 hours (range 1.0-2.5) (PMID 20131255).
Colchicine is demethylated to two metabolites, 2-O-demethylcolchicine and 3-O-demethylcolchicine (2- and 3-DMC, respectively). In vitro studies have shown that hepatic cytochrome P450 3A4 (CYP3A4) is involved in the metabolism of colchicine to 2- and 3-DMC. Colchicine is also a substrate of liver and intestinal P-glycoprotein (P-gp) transporter.
Colchicine is eliminated in urine and stools. 40-65% of orally administrated colchicine is recovered unchanged in urine. Enterohepatic recirculation and biliary excretion account for around 50% of colchicine elimination. The mean half-live elimination is 20 to 40 hours.
Thus, blood concentration of colchicine depends on kidney and hepatic functions, intestinal absorption and secretion, the presence of drug-drug interactions and individual characteristics of CYP3A4 and P-gp activities (PMID 21480191).
The individual CYP3A4 and P-gp activities can be assessed with specific probe and/or substrate of these proteins in the so-called phenotyping assay. Thus, using micro dose of midazolam and fexofenadine the activity of CYP3A4 and P-gp, respectively, can be determined and subsequently the individual pharmacokinetic profile of colchicine characterized (PMID 24722393).
CYP3A4 activity is given by the ratio of hydroxy-midazolam/midazolam assessed 2 hours after an oral administration of 1 mg midazolam (PMID 24722393).
P-gp activity is given by the area under the curve (AUC) of a short kinetic that measures fexofenadine concentrations at 2, 3 and 6 hours after its oral administration of 120 mg (PMID 24722393).
These CYP3A4 and P-gp activities will be correlated with blood colchicine concentrations determined at different time points after an oral administration of 1.5 mg over 1 hour under fasting condition.
The CYP3A4 and P-gp phenotyping will be proposed to all gouty patients who experienced gout flare and who fulfilled the inclusion and exclusion criteria.
Participants will have 3 visits :
Plasma concentrations of colchicine, midazolam, hydroxymidazolam and fexofenadine will be quantified by liquid chromatography-tandem mass spectrometry (PMID 24295116).
Plasma concentrations of colchicine will then correlate to CYP3A4 and P-gp activities estimated by midazolam and fexofenadine metabolism, respectively.
The phenotyping will be performed in 34 colchicine responder and 34 colchicine non-responder patients.
Enrollment
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Inclusion criteria
Patients (> 18 years old) with gout flare defined by following items :
Identification of sodium urate crystals in synovial fluid analysis
Or gout flare diagnosis according to Nijmegen criteria (score > 8/13)
Duration of flare < 48 h
Monoarticular involvement
Exclusion criteria
Primary purpose
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26 participants in 1 patient group
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Central trial contact
Hang-Korng EA, PhD, MD
Data sourced from clinicaltrials.gov
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