Early At-Home Measurement of Adalimumab Concentrations to Guide Anti-TNF Precision Dosing: A Pilot Study.

BACKGROUND AND OBJECTIVE: Underdosing of adalimumab can result in non-response and poor disease control in patients with rheumatic disease or inflammatory bowel disease. In this pilot study we aimed to predict adalimumab concentrations with population pharmacokinetic model-based Bayesian forecasting early in therapy. METHODS: Adalimumab pharmacokinetic models were identified with a literature search. A fit-for-purpose evaluation of the model was performed for rheumatologic and inflammatory bowel disease (IBD) patients with adalimumab peak (first dose) and trough samples (first and seventh dose) obtained by a volumetric absorptive microsampling technique. Steady state adalimumab concentrations were predicted after the first adalimumab administration. Predictive performance was calculated with mean prediction error (MPE) and normalised root mean square error (RMSE). RESULTS: Thirty-six patients (22 rheumatologic and 14 IBD) were analysed in our study. After stratification for absence of anti-adalimumab antibodies, the calculated MPE was -2.6% and normalised RMSE 24.0%. Concordance between predicted and measured adalimumab serum concentrations falling within or outside the therapeutic window was 75%. Three patients (8.3%) developed detectable concentrations of anti-adalimumab antibodies. CONCLUSION: This prospective study demonstrates that adalimumab concentrations at steady state can be predicted from early samples during the induction phase. CLINICAL TRIAL REGISTRATION: The trial was registered in the Netherlands Trial Register with trial registry number NTR 7692 ( www.trialregister.nl ).

Co-administration of cyclosporine and ticagrelor may lead to a higher exposure to cyclosporine: a case report of a 49-year-old man.

ADVERSE EVENT: A drug interaction leading to higher exposure to cyclosporine. DRUGS IMPLICATED: Cyclosporine and ticagrelor. THE PATIENT: A 49-year-old man with a stable renal graft, managed with cyclosporine with stable trough blood concentrations for several years, was treated with ticagrelor for unstable angina pectoris. EVIDENCE THAT LINKS THE DRUG TO THE EVENT: The timeline was consistent with the appearance of an interaction, the interaction was confirmed by an increase in trough concentration of cyclosporine, and there were no alternative causes that by themselves could have caused the increase in cyclosporine exposure. MANAGEMENT: Cessation of ticagrelor. MECHANISM: Inhibition of CYP3A4 and P-glycoprotein by ticagrelor. IMPLICATIONS FOR THERAPY: Clinicians should be aware of this potential interaction as ticagrelor is frequently prescribed in individuals using cyclosporine. Close monitoring of cyclosporine serum concentrations is warranted to avoid overdosing of cyclosporine. A pharmacokinetic study is needed to further examine the probable interaction between cyclosporine and ticagrelor.

Gentamicin serum concentrations in patients with gentamicin-PMMA beads for infected hip joints: a prospective observational cohort study.

BACKGROUND: Gentamicin-polymethylmethacrylate (PMMA) beads release gentamicin gradually, and high concentrations develop only locally. It is unclear how frequent and in which patients gentamicin serum concentrations are measurable and possibly lead to toxicity. The aim of this study was to investigate the measurability of gentamicin serum concentrations after the implantation of gentamicin-PMMA beads and to assess the nephrotoxicity of these beads. METHODS: In this observational cohort study, gentamicin and creatinine concentrations were measured in 34 serum samples of 23 patients with implanted gentamicin-PMMA beads for infected hip joints with our regular immunoassay (lower limit of quantitation 0.4 mg/L). Samples were also analyzed with an adjusted immunoassay with a lower limit of quantitation of 0.05 mg/L. RESULTS: Gentamicin serum concentrations were >0.4 mg/L in 9 of 34 (26%) of all the samples measured (both after the first implantation and change of beads) and in 5 of 23 patients (22%) after the first implantation of gentamicin-PMMA beads. Gentamicin serum concentrations were >0.05 mg/L in 31 samples (91%). Nephrotoxicity (defined as increase in serum creatinine >44 µmole/L and/or a relative increase >25%) occurred more frequently in patients with measurable gentamicin serum concentrations than in those without measurable gentamicin serum levels (57% versus 43%, P = 0.02). Both nephrotoxicity and gentamicin serum concentration could not be associated with the number of implanted gentamicin-PMMA beads. CONCLUSIONS: Gentamicin serum concentrations >0.4 mg/L can be measured after the implantation of gentamicin-PMMA beads in certain patients with infected hip joints. Furthermore, elevated (>0.4 mg/L) gentamicin serum concentrations are associated with nephrotoxicity in patients with gentamicin-PMMA beads for infected hip joints.