Keywords 2 1 linezolid; rifampicin; pharmacokinetics; metabolic enzymes 2 2 2 3 Word count: 1,658 words 2 4 Abstract 2 6Linezolid is an oxazolidinone antibiotic that effectively treats methicillin-resistant 2 7Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE). Since 2 8 rifampicin induces other antibiotic effects, it is combined with linezolid in therapeutic regimes. 9However, linezolid blood concentrations are reduced by this combination, which increases the 3 0 risk of the emergence of antibiotic-resistant bacteria. We herein demonstrated that the 3 1 combination of linezolid with rifampicin inhibited its absorption and promoted its elimination, 3 2 but not through microsomal enzymes. Our results indicate that the combination of linezolid 3 3 with rifampicin reduces linezolid blood concentrations via metabolic enzymes. 3 4 3 5