Details

Autor(en) / Beteiligte

• Litjens, Carlijn H C
• Aarnoutse, Rob E
• van Ewijk-Beneken Kolmer, Eleonora W J
• Svensson, Elin M
• Colbers, Angela
• Burger, David M
• Boeree, Martin J
• te Brake, Lindsey H M

Titel

Protein binding of rifampicin is not saturated when using high-dose rifampicin

Ist Teil von

• Journal of antimicrobial chemotherapy, 2019-04, Vol.74 (4), p.986-990

Ort / Verlag

England: Oxford University Press

Erscheinungsjahr

2019

Quelle

Oxford Journals 2020 Medicine

Beschreibungen/Notizen

• 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 64 mg/L) of rifampicin and in samples obtained by intensive pharmacokinetic sampling of patients who used standard (10 mg/kg daily) or high-dose (35 mg/kg) rifampicin up to steady-state. The performance of total AUC0–24 to predict unbound AUC0–24 was evaluated. Results The in vitro free fraction of rifampicin remained unaltered (∼9%) up to 21 mg/L and increased up to 13% at 41 mg/L and 17% at 64 mg/L rifampicin. The highest (peak) concentration in vivo was 39.1 mg/L (high-dose group). The arithmetic mean percentage unbound to total AUC0–24in 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 AUC0–24 based on total AUC0–24 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.