1. Perception of asthma by patients can be assessed from the relationship between symptom scores and peak expiratory flows. This study was designed to investigate the possibility that medication can affect perception of the sensation of asthma independently of changes in lung function. 2. Twelve subjects whose asthma was inadequately controlled by inhaled bronchodilator alone were studied during four different drug treatments over 3 months. Subjective self-assessment of asthma was scored on a 10 cm visual analogue scale and followed by three consecutive measurements of peak expiratory flow, using a coded electronic peak flow meter. This was recorded not less than three times daily on diary cards. Observations were recorded during the second week of each of four treatments:(i) a run-in period using only inhaled salbutamol as required, (ii) inhaled beclomethasone, (iii) inhaled cromoglycate and (iv) oral theophylline at a dose adjusted to achieve blood levels of 10–20 mg/l. Inhaled salbutamol was permitted during the other treatments as required. Changes in the slope and position of the regression lines of asthma scores on PEF were used to measure changes in perception of asthma on each treatment. Dynamic lung volumes were measured in the clinic before the study and after each treatment period. 3. In the group as a whole, theophylline improved lung function (mean peak flow and dynamic lung volumes) without affecting mean visual analogue scores, beclomethasone improved mean visual analogue scores with much less effect on lung function, while cromoglycate had a small though consistent effect on both. 4. Perception of asthma, measured by the relationship between peak flow rate and visual analogue scores, was unaffected by cromoglycate. On theophylline, perception of asthma was heightened in five subjects despite a definite improvement in their peak flow. On beclomethasone, perception of asthma was reduced in most subjects, often with no discernible improvement in mean peak flow or dynamic spirometry. 5. Perception of bronchoconstriction in asthma can be affected by drugs independently of control of the condition. Theophylline may produce a paradoxical increase in awareness of asthma in some individuals. With beclomethasone therapy a reduction in symptoms of asthma may occur without any improvement in tests of air flow.
1. Airway responses to inhaled salbutamol were measured in two groups of six normal non-atopic subjects. In each group there was a dose-dependent increase in specific airways conductance after salbutamol inhaled in cumulative doses from 25 to 600 μg. 2. In the first group these studies were repeated weekly during and after the subjects had taken regular inhaled salbutamol for 4 weeks, in doses increasing to 500 μg four times daily by week 4. Then, while subjects were continuing to receive regular salbutamol, the studies were repeated after 48 h of inhaled sodium cromoglycate (20 mg four times daily) and again after 48 h of beclomethasone dipropionate (200 μg four times daily). 3. In the second group the studies were repeated after 10 days of regular inhaled salbutamol (500 μg four times daily). 4. There was no change in airway response to inhaled salbutamol after 4 weeks or 10 days regular salbutamol therapy, or after 48 h of sodium cromoglycate or beclomethasone dipropionate therapy. 5. This study did not show the development of resistance to β-agonists in the airways of normal subjects. These findings are discussed in the context of other studies which have shown the development of resistance, and we suggest that there may be a spectrum of susceptibility to the development of impaired airway responsiveness following regular treatment with β-adrenergic drugs.