Pirfenidone works. There have been four randomised placebo-control trials of pirfenidone for the treatment of idiopathic pulmonary fibrosis (IPF); a phase II and phase III study in Japan, and two international multicentre phase III studies.1–3 In all four studies, patients treated with pirfenidone had slower rates of decline in lung volume (vital capacity (VC) in the Japanese studies and forced vital capacity (FVC) in the international studies) than placebo, and in three studies, the results were statistically significant. National Institute of Clinical Excellence (NICE) agrees that pirfenidone has a ‘modest but measurable effect on slowing the decline in lung function’.4 Therefore, whether patients receive pirfenidone depends on whether pirfenidone works enough to justify its cost.

IPF is a chronic progressive disease of unknown aetiology, it is fatal with a median survival of approximately 3 years,5 or less than one electoral cycle. No therapy has been proven to improve survival. Despite the absence of good evidence, various combinations of N-acetylcysteine (NAC), prednisolone and azathioprine have been used for many years to treat patients with IPF. In the early 1990s, a small study suggested that prednisolone and azathioprine might be beneficial,6 and the initial British Thoracic Society (BTS) guidelines for the treatment of cryptogenic fibrosing alveolitis (as IPF was then known) recommended this therapy.7 In 2005, the Idiopathic Pulmonary Fibrosis International Group Exploring N-Acetylcysteine I Annual (IFIGENIA) study demonstrated that NAC might be beneficial in IPF.8 However, this study was criticised at the time for including azathioprine and prednisolone in both the placebo and treatment arms. The inclusion of this faux placebo lead some, possibly correctly, to suggest that NAC was inhibiting the adverse effects of prednisolone and azathioprine, rather than possessing any direct antifibrotic effect. The 2008 BTS IPF guidelines9 implicitly recommended treatment with triple …