Faster and more reliable absorption of adrenaline by aerosol inhalation than by subcutaneous injection

The aim of the present study was to compare absorption of adrenaline given by aerosol spray inhalation with absorption after subcutaneous injection. Arterial plasma adrenaline was measured in nine healthy volunteers following adrenaline administration by both methods. Following inhalation of 20 puffs of adrenaline aerosol, 0.15 mg/puff, a peak arterial adrenaline concentration after 1 min and a rapid fall to baseline from this peak occurred. When given by subcutaneous injection absorption was slower with a peak arterial adrenaline concentration after 4 min. The fall in arterial adrenaline from this peak level was not statistically significant within 30 min after injection. There was less intersubject variation of arterial adrenaline concentration following inhalation when compared with injection. Heart rate, blood pressure and finger tremor followed the changes in arterial adrenaline concentrations. These results indicate that absorption is more reliable when adrenaline is given by inhalation. The rapid fall in arterial adrenaline following inhalation, suggests that repeated inhalations are necessary when such adrenaline therapy is required.