Hypokalaemia induced by inhalation of fenoterol

The effect of inhalation of fenoterol, a beta 2-agonist, on plasma potassium was studied in four groups of four healthy young subjects. Group I received 3 times 2 puffs (0.2 mg fenoterol/puff), group II 3 times 3 puffs, and group III 3 times 4 puffs. Group IV received 3 times 4 puffs of a placebo, according to the group III schedule. The puffs were given at 30-min intervals. Plasma potassium levels decreased significantly in subjects who received fenoterol: the decrease was 0.4 +/- 0.3 (SD) mmol/l in group I, 0.5 +/- 0.2 mmol/l in group II and 0.9 +/- 0.1 mmol/l in group III. In the placebo group plasma potassium levels were unchanged. Inhalation of beta 2-agonists may be dangerous, especially in patients under stress--eg, during an acute asthmatic attack, when the plasma potassium concentration would already be subnormal as the result of raised circulating adrenaline levels.