Aminophylline is related chemically to caffeine, so if you take it or you take theophylline, like many SCLS patients do, which is a more potent and longer-acting version of aminophylline, then you will tend to be much more awake and nervous -- and sometimes downright nasty -- than normal.
The things I've done to cope are (a) I take my medications several hours before going to sleep (say, at 7PM rather than 10PM), to let the effect wear off a bit, and (b) I also take in the evening one of the many anti-anxiety, tranquilizer medications available by prescription -- which, unfortunately, tend to have undesirable side effects of their own.
Your own doctor should be able to help you, because it's a common problem that all asthma patients face; it's not an SCLS-specific thing.