The aim of study is this to evaluate the efficacy and safety of continuous linezolid infusion versus the standard regimen in treating critically ill patients with septic shock in the ICU

it is Prospective randomized controlled study on One hundred forty patients to evaluate the efficacy and safety of continuous linezolid infusion versus the standard regimen in treating critically ill patients with septic shock in the ICU, Initially, each patient will be evaluated for septic shock based on the clinical criteria. Baseline microbiologic specimens will be obtained for all recruited patients through the day of diagnosis including blood C&S. Then, empirical treatment with antibiotics according to expected source of sepsis. Patients with Gram-positive cultures sensitive to Linezolid will be randomly allocated to receive Linezolid in the continuous infusion group (Group A) or conventional intermittent infusion group (Group B) in a 1:1 ratio.

Group A: seventy Patients in the continuous infusion group will receive an intravenous loading dose of 600 mg for 60 min, followed by a continuous infusion of 1200 mg/day (50 mg/h).

Group B: seventy patients in the intermittent infusion group will administrate 600 mg of linezolid IV every 12 h for 60 min.

The treatment period will be 8-10 days in both groups but might decrease or increase based on the patients' clinical response. At the beginning of the study, simple randomization will be used to assign patients using the random numbers set offered by the ICU coordinator. Each patient will be assigned a randomized code consisting of two letters that indicate the intensive care unit and two digits indicating the randomization sequence.

The end point of the study is occurrence of thrombocytopenia (decrease in platelet count ≥ 50% from baseline or a decrease in platelet count ≤ 100 × 103/mm3).

Inclusion Criteria:

• adult patients aged > 18 years old
• diagnosis of septic shock (patient with septic shock can be clinically identified by a vasopressor requirement to maintain a mean arterial blood pressure of 65 mm Hg or greater and serum lactate level greater than 2 mmol\L (>18 mg\dL) in the absence of hypovolemia).
• positive culture confirming linezolid susceptibility.

Exclusion Criteria:

• Patient refusal.
• Known allergy to linezolid.
• Pregnancy and lactation.
• Severe hepatic failure (Child-Pugh C).
• Thrombocytopenia (platelet count < 80,000/mm3).
• Disseminated intravascular coagulation (DIC).
• Hematologic disease, and concurrent use of other medications that may interact with linezolid (i.e., macrolides, serotonin modulators), or drug-associated thrombocytopenia.

. At the beginning of the study, simple randomization will be used to assign patients using the random numbers set offered by the ICU coordinator. Each patient will be assigned a randomized code consisting of two letters that indicate the intensive care unit and two digits indicating the randomization sequence.