Tolerability of prolonged linezolid therapy in bone and joint infection: protective effect of rifampicin on the occurrence of anaemia?

Linezolid therapy has shown high rates of clinical success in patients with osteomyelitis and prosthetic joint infections caused by Gram-positive cocci. Recent studies have demonstrated that linezolid/rifampicin combination therapy prevents the emergence of rifampicin-resistant mutations in vitro. However, linezolid/rifampicin combination-related haematological and neurological toxicities have not been evaluated. To assess the tolerability of prolonged linezolid/rifampicin combination therapy compared with other linezolid-containing regimens in patients with bone and joint infections. We reviewed the medical records of 94 patients who had received linezolid for > 4 weeks after bone and joint infections. Anaemia was defined as a >= 2 g/dL reduction in haemoglobin, leucopenia as a total leucocyte count < 4 x 10(9)/L, and thrombocytopenia as a reduction in platelet count to < 75% of baseline. Anaemia was less frequent among patients on linezolid/rifampicin combination therapy than among patients on linezolid alone or in combination with other drugs (9.3%, 44% and 52%, respectively; P < 0.01). In multivariate analysis, age and treatment group were independently associated with anaemia. Thrombocytopenia was reported in 44% of patients on linezolid/rifampicin combination therapy, in 48% of patients on linezolid alone and in 57.7% of patients on other linezolid-containing regimens. Age was the only variable associated with thrombocytopenia (P = 0.019) in univariate analysis. Linezolid/rifampicin combination therapy was associated with a significantly reduced incidence of anaemia among patients with bone and joint infections, but it did not have an effect on thrombocytopenia and peripheral neuropathy rates. Linezolid/rifampicin combination therapy was not associated with poor clinical outcomes.