Interactions may occur between Theophylline Extended-Release Tablets and a variety of medications. In general, Theophylline Extended-Release Tablets should not be used with lithium salts, diltiazem, verapamil, cimetidine, certain antibiotics, phenobarbital, phenytoin, rifampin, and caffeine or other xanthines. 1. Theophylline extended-release tablets should also not be used with lithium salts because they increase the renal excretion of lithium and interfere with the action of lithium salts; 2. Diltiazem and verapamil can infect the metabolism of theophylline in the liver, and cimetidine can reduce the clearance of theophylline in the liver, and using them together will increase the concentration of Theophylline Extended-Release Tablets in the blood as well as their toxicity; 3. Certain antibiotics, such as erythromycin, roxithromycin and clarithromycin of macrolides, ciprofloxacin and ofloxacin of quinolones can decrease theophylline clearance and increase its blood concentration; 4. Phenobarbital, phenytoin, rifampicin can induce infection to accelerate theophylline clearance, and theophylline also interferes with the absorption of phenytoin; 5. Not to be used together with caffeine or other xanthine drugs, because the same use may increase their effects and toxicity Theophylline extended-release tablets may cause side effects such as nausea and vomiting, insomnia, and agitation in the early stages of administration. Patients with theophylline intolerance, patients with epilepsy, patients with severe cardiac insufficiency, patients with acute myocardial infarction with hypotension, patients with active peptic ulcer, patients with uncontrolled convulsive disorders should not be applied. Nursing females, pregnant women, and those over 55 years of age, need to be used with caution. As a prescription drug, Theophylline Extended-Release Tablets must be used under medical supervision.