The study is planned as a prospective and randomized in patients with VAP. Each patients will receive doripenem in 2 regimens at room temperature (37°C) consecutively: (i) infusion of 0.5 g of doripenem for 4 h via an infusion pump at a constant flow rate every 8 h; (ii) infusion of 0.5 g of doripenem for 1 h via an infusion pump at a constant flow rate every 8 h.