Intervention Patients will be randomized in two groups: the first group will receive 3 days of cloxacillin (150 mg/kg/day) through 4 intermittent infusions/day followed by 3 days of cloxacillin (150 mg/kg/day) through continuous infusion (2 infusions during 12 hours). In the second group the infusion modalities will be inverted and continuous infusion will be preceded by a loading dose. Serum concentrations of cloxacillin will be determined at Day 3 and Days 6 The area under the curve / minimal inhibitory concentration ratio will be use to establish the equivalence between both administration modalities.