DISEASE CHARACTERISTICS:

• Diagnosis of idiopathic pulmonary fibrosis as indicated by 1 of the following:

  • Histologically confirmed usual interstitial pneumonia on surgical lung biopsy

  • Abnormal pulmonary function studies that include the following:

    • Evidence of a restrictive pattern or impaired gas exchange
    • Bibasilar reticular abnormalities with minimal ground glass opacities on high-resolution CT scans
    • Transbronchial lung biopsy or bronchoalveolar lavage showing no features to support an alternative diagnosis

• All other known causes of interstitial lung disease ruled out AND meets ≥ 3 of the following minor criteria:

  • Age > 50 years
  • Insidious onset of otherwise unexplained dyspnea on exertion
  • Duration of illness ≥ 3 months
  • Bibasilar, inspiratory crackles
• Baseline forced vital capacity (FVC) ≥ 50%
• Able to walk ≥ 200 meters without requiring > 6 liters of oxygen per minute as documented by baseline 6-minute walk test

PATIENT CHARACTERISTICS:

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• Able to attend clinic visits
• Baseline systolic blood pressure ≥ 100 mm Hg
• No cigarette or marijuana smoking within the past 6 months
• No history of kidney failure or liver disease
• No allergy or allergic reaction to losartan potassium or any other angiotensin II receptor blocker

PRIOR CONCURRENT THERAPY:

• No prior lung transplant
• More than 1 month since prior and no concurrent immunosuppressant agents (e.g., azathioprine, cyclophosphamide, colchicine, and/or prednisone)
• No other concurrent angiotensin II receptor blocker
• Concurrent coumadin and/or N-acetylcysteine allowed