• plasma antiXa levels at peak after the fourth enoxaparine dose administration
  

• residual plasma antiXa level before the fifth enoxaparine dose administration
  
• activated thromboplastin time
  
• thrombotic events
  
• bleeding events
  

Included patients will be those hospitalized for an acute coronary syndrome with indication of enoxaparin treatment. A same initial dose of 1 mg/kg will be administrated to all patients. According to creatinine clearance, the next doses (every 12 hours subcutaneously) will be adjusted with a 25% dose reduction if creatinine clearance is comprised between 30 and 50 ml/min. After the fourth dose, the anti-Xa plasma levels (main endpoint) will be measured at peak (between 3 and 5 hours after dose administration). Residual values of antiXa will also be measured before the fifth dose administration (secondary criteria).

The objective is to demonstrate a bio-equivalence of efficacy on the anti-Xa values obtained in patients with moderate rela failure compared with patients with creatinine clearance higher than 50 ml/min.

Thrombotic and bleeding events will be recorded during hospitalisation. 140 per-protocol evaluable consecutive patients will have to be obtained: 70 with creatinine clearance higher than 50 ml/min and 70 patients with creatinin clearance between 30 and 50 ml/min.