Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

A product that may interact with this drug is: riociguat.

Other medications can affect the removal of theophylline from your body, which may affect how theophylline works. Examples include cimetidine, disulfiram, fluvoxamine, interferon, mexiletine, rifampin, drugs used to treat seizures (such as carbamazepine, phenytoin), St. John's wort, ticlopidine, viloxazine, among others.

Cigarette/marijuana (cannabis) smoking decreases blood levels of this medication. Tell your doctor if you smoke or if you have recently stopped smoking.

Caffeine and alcohol can increase the side effects of this medication. Avoid drinking large amounts of beverages containing alcohol or caffeine (such as coffee, tea, colas), eating large amounts of chocolate, or taking nonprescription products that contain caffeine.

Theophylline is very similar to aminophylline and oxtriphylline. Do not take medications containing aminophylline or oxtriphylline while using theophylline.

This medication may interfere with certain lab tests (such as blood sugar, cholesterol, uric acid, dipyridamole-thallium imaging tests), possibly causing false test results. Make sure lab personnel and all your doctors know you use this drug.