In a recent issue of Br J Clin Pharmacol Smith et al1 published an outstanding commentary titled ‘Dosing will be a key success factor in repurposing antivirals for Covid-19’. They highlighted that the success in our repurposing efforts will be dependent on ‘getting the dose right’ for drugs which have been developed for different indications and stressed some of the unique challenges of treating this particular disease. They pointed the reader to lopinavir/ritonavir (LPV/r) as an example of a repurposed antiviral and the limited experience of this drug regimen (and other treatments) in the elderly population with comorbidities – ie those most at risk from Covid-19. It is on the issue of comorbidities, polypharmacy and drug-drug interactions (DDIs) that we wish to comment.