Skeletal muscle magnesium and potassium in asthmatics

Skeletal muscle magnesium and potassium in asthmatics treated with oral beta2-agonists. T. Gustafson, K. Boman, L. Rosenhall, T. Sandström, P.O. Wester. ERS Journals Ltd 1996. ABSTRACT: Dietary magnesium has been shown to be important for lung function and bronchial reactivity. Interest in electrolytes in asthma has so far mainly been focused upon serum potassium, especially linked to β2-agonist treatment. It is known that serum levels of magnesium and potassium may not correctly reflect the intracellular status. We therefore investigated whether asthmatics treated with oral β2-agonists had low magnesium or potassium in skeletal muscle and serum, and whether withdrawal of the oral β2-agonists would improve the electrolyte levels. Magnesium and potassium levels in skeletal muscle biopsies, serum and urine were analysed in 20 asthmatics before and 2 months after withdrawal of long-term oral β2-agonists, and for comparison in 10 healthy subjects. Skeletal muscle magnesium in the asthmatics was lower both before (3.62±0.69 mmol·100 g-1 (mean±SD)) and after (3.43±0.60 mmol·100 g-1) withdrawal of oral β2agonists compared with the controls (4.43±0.74 mmol·100 g-1). Skeletal muscle potassium and serum magnesium did not differ between the groups. Serum potassium was significantly lower both before (4.0±0.2 mmol·L-1) and after (3.9±0.2 mmol·L-1) the withdrawal of oral β2-agonists compared with the control group (4.2±0.2 mmol·L-1). The asthmatics had lower skeletal muscle magnesium and lower serum potassium than the healthy controls, both with and without oral β2-agonists. Whether the findings are related to asthma pathophysiology or treatment is currently being investigated. Eur Respir J., 1996, 9, 237–240. *Dept of Internal Medicine, Skellefteå Hospital, Skellefteå, Sweden. **Dept of Pulmonary Medicine and Allergology, Huddinge Hospital, Huddinge, Sweden. Depts of +Pulmonary Medicine and Allergology and ++Internal Medicine, University Hospital of Northern Sweden, Umeå, Sweden.