Sometimes it is not safe to use certain medications at the same time. Some drugs can affect your blood levels of other drugs you take, which may increase side effects or make the medications less effective.
If you take St. John's wort regularly, do not stop taking it without first asking your doctor. Starting or stopping St. John's wort can affect your blood levels of theophylline.
Many drugs can affect theophylline. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here. Tell your doctor about all your current medicines and any medicine you start or stop using.
 Theophylline drug interactions (more detail)
