A placebo-controlled trial of cephalexin therapy in the ambulatory management of patients with cystic fibrosis.

The effects of oral administration of cephalexin were evaluated in a double-blind, 
placebo-controlled, crossover study in 17 patients with mild to moderate pulmonary 
disease due to cystic fibrosis. For two years, four-month periods with 
cephalexin were alternated with four-month placebo periods. Thus, patients served as 
their own control subjects. Fungal vulvovaginitis occurred in two patients during 
cephalexin therapy. During the 2 years of study, the rate of 
colonization with mucoid strains of Pseudomonas aeruginosa increased and disease severity 
deteriorated in patients initially colonized with P. aeruginosa. Short-term courses of 
sputum culture-specific antibiotics improved the course of some patients with mild 
to moderate pulmonary disease due to cystic fibrosis. Treatment with cephalexin 
decreased the frequency of respiratory illnesses, respiratory illnesses requiring antibiotics, and 
hospitalizations for respiratory illnesses in patients initially colonized with Staphylococcus aureus 
and/or Haemophilus influenzae, and also reduced colonization with these organisms. Improved 
weight gain in 16 of 17 patients was associated with periods 
of cephalexin therapy. Pulmonary function tests remained stable or improved in 
10 or 14 patients. Disease severity improved in patients not colonized 
with P. aeruginosa. 