Had asthma my entire life, 46 now. I heard something a few years back too, about a type or maybe a brand of uniphyl was reverting back to it's base chemicals in the bottles on the shelf, that's why it was pulled so fast. I don't know what it breaking down to or why it would not remain stable but that's what I had heard(from a doc).
I know I would take some that would send me around the moon with the shakes at times.
I still get theophylline today and I have loved it from the beginning. I sleep almost too light on it but I never have a night time asthma attack when I use it. Most Docs I know think it's an old-fashioned drug. One Doc told me it's too old to make share holders rich like the newer drugs can, so it gets prescribed less and less. I've had to fight to get to keep it with some Docs during my life but now I have a good Doc that listens.