["We have recently demonstrated that low doses of Dexamethasone 21-P (Dex 21-P), loaded in autologous erythrocytes and administered at monthly intervals, have been able to maintain steroid-dependent patients with Crohn's disease (CD) and ulcerative colitis (UC) in clinical remission with a progressive and complete tapering of systemic steroids.", 'Since multi-drug resistance 1 gene (MDR1) has a potential influence on Dexamethasone (Dex) bioavailability, we designed this study to investigate the correlation between MDR1 genotype and Dex pharmacokinetic after its delivery in patients with inflammatory bowel disease (IBD).', "Seventeen steroid-dependent consecutive patients with IBD (10 UC mean age 36 +/- 12, and 7 Crohn's disease mean age 31 +/- 5) were consecutively recruited. The C3435T polymorphism of MDR1 gene was studied by Denaturing High Performance Liquid Chromatography (DHPLC). Serum level of Dex were determined at the end of the infusion and after 15 days by high performance liquid chromatography electrospray mass spectrometry.", 'The mean dose of Dex 21-P administered was 9.9 mg +/- 4 (range 2.7-20.3), while the mean levels of Dex at the end of the infusion and after 15 days were 0.66 +/- 0.23 mM and 0.06 +/- 0.06 mM, respectively. Concerning the C3435T genotype, two patients were wild-type, eleven heterozygotes, and four homozygotes. No correlation between basal or 15-days plasma level of Dex and MDR1 genotype was found (r = 0.19 and r = 0.21, respectively).'] Does the polymorphism of multi-drug resistance 1 gene ( MDR1 ) influence the pharmacokinetics of dexamethasone loaded into autologous erythrocytes of patients with inflammatory bowel disease?