Theophylline is a phosphodiesterase inhibitor used in the treatment of asthma, has a narrow therapeutic range and can cause cardiac, metabolic and neurological disorders at toxic doses. Clinical signs of poisoning are: nausea, vomiting, tachycardia, hypotension, impaired consciousness, convulsion, metabolic acidosis and hypokalemia. Diagnosis is made according to the history and level of intake. If the blood level can be measured, acute ingestion of less than 40 micrograms/mL indicates mild, 40100 indicates moderate, and over 100 indicates severe poisoning. In addition to symptomatic treatment, multiple activated charcoal applications, hemodialysis, or hemoperfusion are recommended. Hemoperfusion should be performed if the blood theophylline level is over 90 at any time or if there is convulsion or hypotension or ventricular arrhythmia or unstoppable vomiting when it is over 40.