Study to compare the bioavailability of 350 mg Bronchoretard® - a sustained-release theophylline (anhydrous) product with respect to the reference product, Theo Dur® 300 mg theophylline anhydrous (sustained-release product) by comparing the rate and extent of absorption of theophylline based on both single and multiple-dose profiles.

Inclusion Criteria:

• Healthy, non-smoking male subjects between 18 and 45 years of age
• Body weight within 10% of the ideal weight according to the Body Mass Index (BMI)
• Normal health based on medical history and findings within the range of clinical acceptability, in respect of the physical examination (including electrocardiogram and vital signs) and special investigations
• Ability to comprehend and willingness to sign both statements of informed consent (for screening and study-specific procedures)

Exclusion Criteria:

• History of serious systemic or organ disease
• A major illness during the 3 months before commencement of the study-related procedures
• Significant physical or organ abnormality
• History of hypersensitivity to theophylline or other xanthine derivatives
• Use of any medication within 2 weeks before the first administration of study medication
• Participation in another study with an experimental drug within 8 weeks before the first administration of study medication
• Treatment within the previous 3 months with any drug with a well-defined potential for adversely affecting a major organ or system (for example chloramphenicol, which may cause bone marrow suppression)
• Donation of blood during the 8 weeks before the first administration of study medication
• History of, or current compulsive alcohol abuse (> 10 drinks per week), of regular exposure to other substance of abuse
• Positive testing for HIV and hepatitis B antigens within the previous 3 months