OBJECTIVES: I. Determine the safety and efficacy of tobramycin in patients with cystic fibrosis who are chronically colonized with Pseudomonas aeruginosa.

II. Determine whether this treatment produces tobramycin-resistant bacteria at a frequency different from the placebo group and whether the emergence of resistance is associated with a lack of clinical response.

PROTOCOL OUTLINE: This is a randomized, double blind, placebo controlled, multicenter study.

Patients receive tobramycin or placebo by inhalation twice daily for 28 days followed by 28 days of rest. This treatment is repeated twice, for a total of 3 courses of therapy.

Patients are followed every 2 weeks for the first 8 weeks, then every 4 weeks, and then at 4 weeks after the last treatment.

PROTOCOL ENTRY CRITERIA:

--Disease Characteristics--

Documented cystic fibrosis with Pseudomonas aeruginosa present in a sputum or throat culture within 6 months prior to screening

Sweat chloride at least 60 mEq/L

--Prior/Concurrent Therapy--

At least 14 days since prior intravenous or aerosolized tobramycin or other antipseudomonal antibiotic

At least 4 weeks since prior administration of any investigational drug

No concurrent antibiotics by aerosol

--Patient Characteristics--

Renal:

• Creatinine less than 2 mg/dL
• BUN less than 40 mg/dL
• No proteinuria of 2+ or greater

Pulmonary:

• FEV1 at least 75% and at least 25% of predicted
• Room air oximetry at least 88% saturation
• Able to perform pulmonary function tests
• No hemoptysis of 60 mL or greater within 30 days prior to study
• No abnormal chest X-ray

Other:

• Not pregnant
• Fertile females must use effective contraception
• No history of positive culture with Burkholderia cepacia
• No history of glucose-6-phosphate dehydrogenase deficiency
• No known local or systemic hypersensitivity to aminoglycosides, albuterol, or other beta-2 agonists