Every year NHS organisations painstakingly estimate the likely expenditure on medicines in order to establish a realistic drugs budget to meet the needs of their patients. Predicting such expenditure involves extrapolating from current prescribing patterns and adjusting for factors that increase costs (e.g. changes in demographics, the requirement to fund nationally approved medicines, the launch of new medicines) as well as those factors that help to reduce costs (e.g. medicines coming off patent, availability of biosimilars, initiatives to reduce wastage of medicines).1 In 2013/2014, the NHS across the UK spent over £15 billion on medicines in primary and secondary care. In England, the drugs …