Introduction
Due to its significant effect on morbidity, asthma represents an important NHS priority area, where national guidelines exist. However, treatment success depends, at least partly, on patients' compliance with recommendations. Among the many factors that impact on patients' management decisions, one that has had little research attention in the UK is that of medication cost. Previous work has shown that bronchodilator and steroid inhalers were among those commonly not dispensed on cost grounds. The aim of this study was to explore asthma patients' views of prescription charges and how the cost of them affected their management behaviour.

Method
Three General Practices in the Northwest of England mailed 602 asthma patients aged between 18 and 59, thus encompassing those potentially paying prescription charges. Fifty-two patients responded, and 30 were interviewed in-depth, using a topic guide covering the interviewee's asthma, what influenced how they managed it, and if, and how, cost played a role. More general views on the prescription charge policy were also explored.

Results
Twenty-one (70%) interviewees were women, the mean age was 44 (range: 21 to 59). Due to the study focus, interviewees either paid individual charges (n = 24) or had pre-payment certificates (n = 6). Most interviewees had at least two types of inhalers, 'reliever' and 'preventer.' Formal self-treatment plans did not seem to be in place, but several interviewees adjusted their asthma management themselves, some following GP guidance, others basing this on their own experience. They used various strategies to keep cost to a minimum, for example, they tried lifestyle adjustments to avoid the use of inhalers, or tried not to have more than one item due for renewal on a repeat prescription. Most interviewees realised the importance of their inhalers and balanced their cost against other things. Nevertheless, a few interviewees used their treatment sub-optimally, purely on cost grounds, affecting treatment outcome negatively. Several interviewees knew pre-payment certificates existed, yet the episodic and unpredictable nature of asthma made it difficult to anticipate whether they would benefit. Even though most accepted the principle of paying towards medication, many resented the inequity in the current policy of medical exemptions. They could not understand why some chronic conditions were exempt, yet asthmatics had to pay. There was a clear awareness that their condition was chronic and taking their medication helped to prevent adverse episodes, which would have health and NHS resource implications. This brought many interviewees to the conclusion that conditions requiring long-term drug therapy, should either be exempt from charges or subsidised.

Discussion
Even though the cost of the prescription charge only appeared to have a negative impact on health outcome for very few, it did impact on many. This work strengthens existing evidence that, for those that pay, cost is a factor in management decisions. It highlights the inequities in the current policy, particularly in relation to medical exemptions. Furthermore, it demonstrates a novel reason for how the intended protection mechanism offered by pre-payment certificates may be failing for episodic and unpredictable conditions.