The biochemical effects of high-dose inhaled salbutamol in patients with asthma

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Abstract
We have studied the biochemical effects of high doses of inhaled salbutamol in 14 asthmatic patients age 38 years, FEV1 62%. Cumulative doubling doses of inhaled salbutamol were given every 20 min as follows: 100 µg, 200 µg, 500 µg, 1000 µg, 2000 µg, 4000 µg. Plasma glucose, potassium, and magnesium were measured at each step of the doseresponse curve. Salbutamol produced significant hypokalaemic and hyperglycaemic effects, but no significant change in magnesium. There were linear log-dose responses for both glucose (r/it=0.58) and potassium (r=−0.46). There were wide individual variations in maximum responses to salbutamol 4000 µg (as means and 95% confidence intervals): Δ glucose 1.46 (0.83 to 2.09) mmol/l, Δ potassium −0.38 (−0.64 to −0.12) mmol/l. Thus, hypokalaemic and hyperglycaemic effects may occur with doses of salbutamol similar to those curently used for nebulizer therapy (2.5–5 mg). We postulate that during acute exacerbations of airflow obstruction these changes may be accentuated and become clinically relevant.