In the clinic, phage therapy often is used in combination with antibiotics, including against Pseudomonas aeruginosa infections. Antibiotics, however, interfere with critical bacterial functions, including DNA replication and protein synthesis, that are required for phage infection success. Nevertheless, the impact of antibiotics on phage replication is not commonly determined prior to phage therapies. Here we use an optical density-based ‘lysis profile’ assay to assess the impact of two classes of antibiotics – meropenem, and tobramycin – on the bactericidal, bacteriolytic, and virion-production activities of P. aeruginosa phages PEV2 and fKMV. This is a rapid, high-throughput assay that provides results of phage-antibiotic interactions within a few hours, e.g., as could be employed prior to the start of phage-antibiotic combination treatments. The antibacterial activities of phages and antibiotics in combination were found to be greater than those of phages or antibiotics alone. Tobramycin, however, substantially interfered with phage bacteriolytic and virion-production activities, even at minimum inhibitory concentrations (MICs). Meropenem, by contrast, had no or minimal impact including at clinically relevant concentrations (up to 27× MIC). We corroborated these results by more traditional measurements: colony forming units, plaque forming units, and one-step growth experiments. Furthermore, we analyzed activity of mono- and combination therapies against biofilm. Collectively, this indicates that meropenem may be minimally antagonistic in phage therapy co-treatments of P. aeruginosa infections. More generally, our results point to a prospect of rapid, routine testing of antibiotic antagonism of phage infection activities prior to the initiation of phage treatments.