Qvar Versus Clenil, a General Practice Research Database Study

Current asthma guidelines in the UK are underpinned by evidence derived from randomised controlled trials (RCTs). Although RCT data are considered the gold standard, patients recruited to asthma RCTs are estimated to represent less than 10% of the UK's asthma population. The poor representation of the asthma population is due to a number of factors, such as tightly-controlled inclusion criteria for RCTs. There is, therefore, a need for more representative RCTs and real-life observational studies to inform existing guidelines and help optimise asthma outcomes. In response to the Montreal Protocol's ruling to phase out ozone-depleting chlorofluorocarbon (CFC) propellants in asthma inhalers, several hydrofluoroalkane-134a-propellant (HFA-) formulations of BDP have been developed. Two branded generic formulations currently available in the UK are Qvar® (Teva Pharmaceutical Industries Ltd) - an extra-fine-particle (\~1.1 microns) HFA-BDP (solution) formulation and Clenil® (Chiesi Limited) - a larger particle (\~2.9 microns) HFA-BDP (suspension) formulation. The extra-fine particle formulation HFA-BDP formulation (Qvar®) has been shown to improve total and small airway deposition relative to CFC-BDP. As a result of the more even distribution through both the large and small airways of the lungs and data from short-term randomised clinical trials (RCTs), Qvar® dosing is recommended at approximately one half the dose of traditional CFC-BDP (average particle size \~3.5 microns). However, the larger-particle Clenil® is recommended for prescribing at the same dose as traditional CFC-BDP. Further studies are required to understand whether the differences in particle size and airway distribution have an impact on asthma outcomes over the long-term. This observational study will investigate the real-world effectiveness of extra-fine HFA-BDP (Qvar®) as compared with larger-particle HFA-BDP (Clenil®) in patients with asthma who: were new to ICS therapy; received an increase in their ICS dose, or switched / changed baseline ICS therapy to HFA-BDP with no change in BDP-equivalent ICS dose. We hypothesise that differences in effectiveness might become apparent over the longer term through a retrospective database analysis of one-year outcomes for the diverse patient population seen in primary care.