INTRAVENOUS THEOPHYLLINE-INDUCED EXCRETION OF CALCIUM, MAGNESIUM AND SODIUM IN PATIENTS WITH RECURRENT ASTHMATIC ATTACKS

Hypomagnesaemia in a woman treated with theophylline and albuterol bec ause of recurrent asthmatic attacks prompted us to explore the effects of these drugs on the metabolism of magnesium, calcium, sodium and ph osphate in such patients. Theophylline given intravenously to 10 femal es with recurrent asthmatic attacks increased total mean urinary excre tion (mean +/- SEM, mmol 5 h-1) of Mg from 0.54 +/- 0.07 to 0.86 +/- 0 .10; of Ca from 0.89 +/- 0.18 to 1.45 +/- 0.26; of Na from 22.9 +/- 7. 5 to 49.44 +/- 9.5. Theophylline i.v. and an inhaled beta2-agonist (al buterol) both increased the normal morning-till-noon serum concentrati on difference (mean +/- SEM, mmol l-1) in PO4 (from -0.13 +/- 0.04 to -0.23 +/- 0.03 and -0.23 +/- 0.04, respectively) and reduced the norma l increase in serum-K (from 0.25 +/- 0.07 to 0.06 +/- 0.08 and -0.13 /- 0.09, respectively). Disproportional changes in serum and urinary l evels of magnesium and calcium by theophylline i.v. is suggestive of M g depletion of intracellular stores and a negative calcium balance. Th eophylline, therefore, may exert adverse effects on the metabolism and urinary excretion of calcium and magnesium in subjects with recurrent asthmatic attacks.