Oral salbutamol decreases serum digoxin concentration

The effect of a therapeutic dose of oral salbutamol on serum and skeletal muscle digoxin concentrations has been studied in volunteers digitalised with digoxin. On one occasion a biopsy was taken from the quadriceps after 2 h of supine rest and then 3-4 mg salbutamol was given orally. Blood samples were taken before and after that dose and another muscle biopsy specimen was taken from the same thigh 180 min after the medication. On another occasion control blood sampling, ECG and blood pressure recordings were made but without muscle biopsies or salbutamol administration. Compared to the control measurements, salbutamol decreased the serum digoxin concentration (0.30 nmol.l-1). It also reduced the serum potassium concentration (0.58 mmol.l-1). The digoxin concentration in skeletal muscle did not change significantly after the intake of salbutamol. Thus, even a therapeutic oral dose of salbutamol reduces the serum digoxin concentration in man.