Bronchodilator action of inhaled fenoterol and ipratropium in normal subjects: a teaching exercise for medical students.

1. A pharmacology practical class for preclinical medical students was designed as a placebo-controlled, double-blind trial of two bronchodilator drugs. 2. Fenoterol hydrobromide (800 micrograms), ipratropium bromide (80 micrograms) and placebo (propellant only) were given by metered dose inhaler to 79 non-asthmatic volunteers. Their effects on FEV1, heart rate and tremor (assessed by the time taken to thread five sewing needles) were compared. 3. Both drugs caused a significant increase in FEV1: the largest group mean increase was 77 ml, recorded 15 min after fenoterol, and 103 ml, recorded 60 min after ipratropium. 4. Fenoterol also caused a mean increase of 8.7 beats min-1 in heart rate, 5 min after inhalation. This effect was still apparent after 60 min. 5. Fenoterol appeared to prolong needle threading time in some individuals. 6. In subjects who inhaled fenoterol, there were no correlations between the increase in FEV1, the increase in heart rate, or the development of tremor. 7. It is concluded that inhaled fenoterol and ipratropium both cause bronchodilation in normal subjects. Systemic absorption of fenoterol is indicated by the rapid increase in heart rate. The bronchodilator effect of ipratropium suggests that resting airway calibre is governed partly by parasympathetic tone in normal subjects. 8. The bronchodilator and systemic effects of these drugs can be used to demonstrate pharmacological, therapeutic and statistical principles to medical students.