Hi
Theophyllin has been a life saver for me. Don't know what i'd do without it. I did have lots of side effects to start with but they have worn off and weren't much worse than with ventolin. Be careful of your pottassium levels though, and if you feel sick when you've taken it try taking the next dose after food, that helps me. Teophyllin is used to treat asthma by opening up the airways and relieving bronchospasm. The one i take is a 12 hour release capsule, it works in the same way as seretide.
If you have side effects with it you should see your doctor again,.
Good luck and breathe easy