Laboratory experiments suggest that rapid cycling of antibiotics during the course of treatment could successfully counter resistance evolution. Drugs involving collateral sensitivity could be particularly suitable for such therapies. However, the environmental conditions in-vivo differ from those in-vitro. One key difference is that drugs can be switched abruptly in the lab, while in the patient, pharmacokinetic processes lead to changing antibiotic concentrations including periods of dose overlaps from consecutive administrations. During such overlap phases, drug-drug interactions may affect the evolutionary dynamics. To address the gap between the lab and potential clinical applications, we set up two models for comparison - a `lab model' and a pharmacokinetic-pharmacodynamic `patient model'. The analysis shows that in the lab, the most rapid cycling suppresses the bacterial population always at least as well as other regimens. For patient treatment, however, a little slower cycling can be preferable if the pharmacodynamic curve is steep or if drugs interact antagonistically. For rapid (unlike slow) regimens, collateral sensitivity brings no visible benefit in the considered range of doses when resistance is absent prior to treatment. By contrast, drug-drug interactions strongly influence the treatment efficiency of rapid regimens, demonstrating their importance for the optimal choice of drug pairs.