At least a third of patients in Britain aged more than 75 years are taking four or more drugs. Adverse drug reactions are implicated in 5% to 17% of hospital admissions. Hence the dictum “first, do no harm” becomes prescient. Doctors need to be able to critically assess a patient's treatments. Waste is substantial: £19 000 ($35 000; €29 000) worth of drugs were returned to pharmacies over an eight week period in Gwent.