| 1. |
- Litjens, Carlijn H. C., et al.
(författare)
-
Protein binding of rifampicin is not saturated when using high-dose rifampicin
- 2019
-
Ingår i: Journal of Antimicrobial Chemotherapy. - : OXFORD UNIV PRESS. - 0305-7453 .- 1460-2091. ; 74:4, s. 986-990
-
Tidskriftsartikel (refereegranskat)abstract
- Background Higher doses of rifampicin are being investigated as a means to optimize response to this pivotal TB drug. It is unknown whether high-dose rifampicin results in saturation of plasma protein binding and a relative increase in protein-unbound (active) drug concentrations. Objectives To assess the free fraction of rifampicin based on an in vitro experiment and data from a clinical trial on high-dose rifampicin. Methods Protein-unbound rifampicin concentrations were measured in human serum spiked with increasing total concentrations (up to 64mg/L) of rifampicin and in samples obtained by intensive pharmacokinetic sampling of patients who used standard (10mg/kg daily) or high-dose (35mg/kg) rifampicin up to steady-state. The performance of total AUC(0-24) to predict unbound AUC(0-24) was evaluated. Results The in vitro free fraction of rifampicin remained unaltered (approximate to 9%) up to 21mg/L and increased up to 13% at 41mg/L and 17% at 64mg/L rifampicin. The highest (peak) concentration in vivo was 39.1mg/L (high-dose group). The arithmetic mean percentage unbound to total AUC(0-24)in vivo was 13.3% (range=8.1%-24.9%) and 11.1% (range=8.6%-13.6%) for the standard group and the high-dose group, respectively (P=0.214). Prediction of unbound AUC(0-24) based on total AUC(0-24) resulted in a bias of -0.05% and an imprecision of 13.2%. Conclusions Plasma protein binding of rifampicin can become saturated, but exposures after high-dose rifampicin are not high enough to increase the free fraction in TB patients with normal albumin values. Unbound rifampicin exposures can be predicted from total exposures, even in the higher dose range.
|
|
| 2. |
- Svensson, Robin J., et al.
(författare)
-
Model-Based Relationship between the Molecular Bacterial Load Assay and Time to Positivity in Liquid Culture
- 2019
-
Ingår i: Antimicrobial Agents and Chemotherapy. - 0066-4804 .- 1098-6596. ; 63:10
-
Tidskriftsartikel (refereegranskat)abstract
- The molecular bacterial load (MBL) assay is a new tuberculosis biomarker which provides results in ∼4 hours. The relationship between MBL and time-to-positivity (TTP) has not been thoroughly studied, and predictive models do not exist. We aimed to develop a model for MBL and identify the MBL-TTP relationship in patients. The model was developed on data from 105 tuberculosis patients from Malawi, Mozambique, and Tanzania with joint MBL and TTP observations quantified from patient sputum collected for 12 weeks. MBL was quantified using PCR of mycobacterial RNA and TTP using the mycobacterial growth indicator tube (MGIT) 960 system. Treatment consisted of isoniazid, pyrazinamide, and ethambutol in standard doses together with rifampin 10 or 35 mg/kg of body weight. The developed MBL-TTP model included several linked submodels, a component describing decline of bacterial load in sputum, another component describing growth in liquid culture, and a hazard model translating bacterial growth into a TTP signal. Additional components for contaminated and negative TTP samples were included. Visual predictive checks performed using the developed model gave good description of the observed data. The model predicted greater total sample loss for TTP than MBL due to contamination and negative samples. The model detected an increase in bacterial killing for 35 versus 10 mg/kg rifampin (P = 0.002). In conclusion, a combined model for MBL and TTP was developed that described the MBL-TTP relationship. The full MBL-TTP model or each submodel was used separately. Second, the model can be used to predict biomarker response for MBL given TTP data or vice versa in historical or future trials.
|
|
