Background and Importance The Antimicrobial Therapy Guidelines recommend the conventional dosage of linezolid (600 mg every 12 hours) for patients on haemodialysis (HD). Linezolid dialyzes 40% by HD.

Aim and Objectives Monitoring plasma concentrations of linezolid in a patient on HD.

Material and Methods A 63-year-old man with a history of bypass with saphenous vein and stage-4 of chronic kidney disease on an HD programme, was admitted to the intensive care unit (ICU) for septic shock due to an ischiorectal abscess.

Enterococcus faecium sensitive to linezolid (MIC 2) was isolated from the abscess culture and linezolid treatment (600 mg every 12 hours) was started. During his stay at the ICU, he underwent daily continuous haemodiafiltration.

After that, he was transferred to the ward where he underwent three conventional high flow HD sessions per week.

Upon arrival at the ward, we were asked to monitor linezolid levels due to probable toxicity associated with a decrease in platelets (196,000/mcl at that moment vs. 441,000/mcl prior to linezolid).

Results After 12 days of linezolid treatment, a trough level of 12.6 mcg/ml was obtained (range 2 – 7 mcg/ml). We recommended to discontinue the linezolid treatment and to measure the trough level again the next day before and after HD. The levels found were 6.71 and 1.26 mcg/ml respectively (HD elimination rate of 81.22%). Thus, we advised to restart with a dosage of 600 mg every 24 hours that same night.

During the following days, we recommended to continue with the same dosage guided by pre- and post-HD levels. The platelet count increased progressively after establishing levels within the therapeutic range.

Conclusion and Relevance This clinical case demonstrates that there may be patients undergoing HD who have toxic levels of linezolid with the standard dosage. In these cases, there is a need to monitor and adjust the dose.

We have also observed that the HD elimination in this patient differs from the value reported by the Antimicrobial Therapy Guidelines probably due to the different type of HD membrane.

Conflict of Interest No conflict of interest.