Some fundamental points concerning the clinical aspects of desensitization.

Continued exposure of target cells to a hormonal agonist frequently leads to a blunted response to that agonist. This process has been termed desensitization, refractoriness, tolerance or tachyphylaxis. The receptor involved in case of beta-sympathomimetics is the beta-adrenergic receptor. When the clinical aspects of beta-adrenergic receptor desensitization are considered, a number of points need serious attention: 1) the route of administration of the drug and the concentration of the drug reached at the receptor site; 2) other factors which may cause reduced responsiveness of the beta-adrenergic receptor besides beta-sympathomimetics and interfere with this process; 3) the different cell-types which are studied and thought to be representative for processes taking place at lung tissue level; 4) the in vivo parameter(s) chosen to describe desensitization; 5) the difference between normal and asthmatic subjects; 6) the mechanism behind desensitization. The paper concerns a review of these points. Since the clinical findings with respect to the induction of desensitization by beta-sympathomimetics are rather controversial, the therapeutic advice should be: use it with caution.