Which of the following should be monitored if linezolid is given for more than 14 days?

Because of the increase in multi-drug-resistant strains of gram-positive bacteria, the development of new and novel-acting antimicrobial agents is at the forefront of pharmaceutical research. Currently, the prevalence of methicillin-resistant staphylococci (MRSA) and vancomycin-resistant enterococci (VRE) is a major clinical problem. Linezolid (Zyvox(r)-Pfizer) is an antimicrobial agent of the oxazolidinone class that possesses a wide spectrum of activity against gram-positive organisms, including MRSA and VRE. Because of linezolid's novel mechanism of action, cross-resistance with other antimicrobial agents is not expected. Linezolid is therefore a ble option for ceain types of infectious disease. Linezolid should not be used for empiric therapy, except under unusual circumstances, or to treat mild gram-positive infections where other antimicrobial agents would be effective. Thrombocytopenia has been repoed in patients treated with linezolid. Platelet levels in most patients returned to normal during the follow-up period. The risk of thrombocytopenia appears to be related to duration of therapy. Platelet counts should be monitored at baseline and at least every 7 days during treatment.