The paradoxical effect of adrenergic and methylxanthine drugs in cystic fibrosis.

This study examined the effect of aerosolized isoproterenol and oral theophylline on 
pulmonary function in cystic fibrosis (CF) to determine how often these 
drugs are beneficial and whether there is a correlation between response 
to isoproterenol and response to oral theophylline. After obtaining baseline pulmonary 
function tests before and after isoproterenol aerosol, 12 patients with CF 
were put on a double-blind trial of high-dosage theophylline (10 mg/kg 
three times per day) or placebo for four weeks and were 
then switched to the alternate regimen for the next four weeks. 
Patients had weekly evaluations of pulmonary function and plasma theophylline determinations. 
Gastrointestinal side effects were common with theophylline. The responses to aerosolized 
bronchodilators were inconsistent from week to week. After aerosolized bronchodilator, five 
of 12 patients had an average increase of 10% or more 
in FEF45%- 55% and FEF70%-80%. While taking oral theophylline, five patients 
had a 10% or more decrease in FEF 45%-55% and six 
patients had a decrease in FEF70%-80%. We conclude that there was 
no concordance between response to isoproterenol and theophylline, and that adrenergic 
and methylxanthine drugs must be used with caution in patients with 
CF. 