Criteria for the clinical evaluation of prophylactic agents in bronchial asthma.

The clinical investigation of prophylactic agents for bronchial asthma is at once simple and laborious: simple because provocation tests are available for measuring the bronchial reactivity of the asthma patient to numerous stimuli and his response to treatment; but laborious because some of these methods are poorly standardised and above all because bronchial spasticity varies greatly from patient to patient and in the same patient at different times. The fluctuating pattern of asthma, is, moreover, an obstacle to clinical investigation. It has to be taken into account in devising trial protocols. Besides bias associated with the disorder itself, there are other difficulties inherent in the prophylactic nature of the treatment. It is a simple enough matter to evaluate the activity of a bronchodilator since the effect of such a compound is directly measurable. Evaluation of the efficacy of a prophylactic agent is more difficult since the fluctuations in episodes of bronchoconstriction and in the bronchodilator treatment needed for these episodes have to be evaluated jointly. We shall have occasion to revert to the practical consequences of this later.