 This paper investigates the potential drug-drug interactions between two commonly prescribed medicines, salbutamol and fluvoxamine. It uses a physiologically based pharmacokinetic, PBPK, model to simulate the effects of co-administration on the concentration of both drugs in the body. The results suggest that co-administration of these two drugs may increase the concentration of salbutamol in some scenarios, such as when the patient is older or has a higher dose of fluvoxamine. This could have implications for patient safety, as it means that the therapeutic benefits of salbutamol may not be achieved if taken alongside fluvoxamine. Therefore, it is important to monitor patients who are taking multiple medications regularly, regardless of their age or other characteristics, to ensure they receive the maximum benefit from their treatments. This article was authored by Laura Marquez and Nuno Vale.