Tobramycin Inhalation Powder (TIP) Administered Once Daily Continuously Versus TIP Administered BID in 28 Day on / 28 Day Off Cycles

Inclusion Criteria: 1. Provide written informed consent, HIPPA (Health Insurance Portability and Accountability Act) authorization (where applicable), and assent (as appropriate) prior to the performance of any study-related procedure. 2. Confirmed diagnosis of CF 3. FEV1 at screening (Visit 1) ≥25% and ≤ 80% of normal predicted values for age, sex, and height 4. P. aeruginosa must be present within 6 months prior to screening and at screening 5. Able to comply with all protocol requirements 6. Clinically stable in the opinion of the investigator Exclusion Criteria: 1. History of Burkholderia cenocepacia (Bcc) complex within 2 years prior to screening and/or Bcc complex at screening 2. Hemoptysis more than 60 cc at any time within 30 days prior to study drug administration 3. History of hearing loss or chronic tinnitus deemed clinically significant by the investigator 4. Serum creatinine 2 mg/dL or greater, BUN 40 mg/dL or greater, or an abnormal urinalysis defined as 2+ or greater proteinuria at screening 5. Known local or systemic hypersensitivity to aminoglycosides or inhaled antibiotics 6. Patients who are unable to discontinue previously received inhaled antibiotic regimen(s) (inhaled antibiotics are not allowed other than study drug) 7. Use of inhaled aminoglycosides within 28 days prior to study drug administration (Visit 2) 8. Use of systemic anti-pseudomonal antibiotics within 28 days prior to study drug administration 9. Use of loop diuretics within 7 days prior to study drug administration 10. Administration of any investigational drug within 30 days prior to enrollment or 5 half-lives, whichever is longer 11. Signs and symptoms of acute pulmonary disease, e.g , pneumonia, pneumothorax 12. Hospitalization during the baseline visit 13. History of malignancy 14. Patients with clinically significant laboratory abnormalities (not associated with the study indication) at screening 15. Patients with other clinically significant conditions (not associated with the study indication) which might interfere with the assessment of this study 16. Patients or caregivers with a history of noncompliance to medical regimens and patients or caregivers who are considered potentially unreliable 17. Pregnant or nursing (lactating) women 18. Women of child-bearing potential, defined as all women physiologically capable of becoming pregnant, including women whose career, lifestyle, or sexual orientation precludes intercourse with a male partner and women whose partners have been sterilized by vasectomy or other means, UNLESS they are using two birth control methods. Other protocol-defined inclusion/exclusion criteria may apply.