A Study of Patient Responses to a Perceived Change in Salbutamol Metered Dose Inhalers

Experience in the clinic reveals that some patients have attributed negative changes in their respiratory health status to generic substitution of inhaled medications, even though — from a pharmacological perspective — therapeutic equivalence would be expected. The objective of this study was to evaluate patient-reported changes in efficacy or toxicity following a perceived switch of an inhaled drug product. Forty-eight patients with air flow limitation had their usual brand of salbutamol metered-dose inhaler (MDI) replaced for one week with a new MDI. Patients were not informed that the replacement MDI was exactly the same brand as their usual MDI, and the product identity was disguised by a label. Forced expiratory volume in one second, respiratory symptoms and MDI use were compared between the week when the patients knew they were using their usual brand of MDI and the week they were using the perceived new MDI. Patient MDI preference was assessed at the end of the study. Even though there was no change in the brand of salbutamol MDI, 46 per cent of patients thought that the new MDI was better at managing their symptoms, 27 per cent thought that the new MDI was worse and 27 per cent perceived no difference (p<0.05 for rejecting the null hypothesis that all responses would be for no difference). Seventy per cent of patients stated that they had a preference for one MDI over the other, even though there had been no change in inhaler. Factors other than product differences are likely to be responsible for patient claims of changes in respiratory health status subsequent to generics substitution with inhaled medications when equivalent products are used. If such changes are reported following the introduction of a new generic product, the changes may be incorrectly attributed to the new product, confounding the ability to assess the quality of the new product in post-marketing evaluation.