[Sympathicomimetics and development of tolerance (author's transl)]

The development of tolerance to sympathicomimetics caused by continuous application was investigated as well in patients as in normal subjects. In 70 non-selected patients with obstructive airway disease the decrease of airway resistance was examined after inhaling 2 puffs of salbutamol. Patients showing a reduction of airway resistance less than 20% were examined more closely. Possible explanations for their decreased response to salbutamol were as follows: a considerable dyscrinism in 10 patients, a mucosal swelling caused by bronchopulmonary infection in 3 patients, a previous pulmonary embolism in 2 patients. No explanation could be found in 2 cases, in one of them - an analgetic asthma - the slight response was reproducible. The problem of desensitization or development of tolerance does not seem to be very significant in the in-patients. In 5 normal subjects the response of airway resistance, heart rate and blood pressure was investigated before and 30 minutes after inhaling 2,4 and 6 puffs of salbutamol. The tests were repeated after 1,2 and 3 weeks of application of 2 puffs of salbutamol 5 times a day. No positive reference to a substantial difference in tolerance after protracted administration of salbutamol could be found. Thus there is no evidence of development of tolerance to salbutamol.