In a retrospective study that compared 0.5 h piperacillin/tazobactam infusions (3.375 g, q6h) with 4-h infusions (3.375 g, q8h) in patients infected with P. aeruginosa, the 4-h infusions reduced 14-day mortality from 31.6% to 12.2% (P = 0.02) and median length of stay from 38 to 21 days in patients with APACHE II scores 17 (P = 0.02).