Theophylline is a dimethylxanthine having the two methyl groups located at positions 1 and 3. It is structurally similar to caffeine and is found in green and black tea. It has a role as a bronchodilator agent, a vasodilator agent, a drug metabolite, an anti-asthmatic drug, an EC 3.1.4.* (phosphoric diester hydrolase) inhibitor, an immunomodulator, a muscle relaxant, an anti-inflammatory agent, an adenosine receptor antagonist, a fungal metabolite and a human blood serum metabolite. Theophylline is a competitive nonselective phosphodiesterase inhibitor and nonselective adenosine receptor antagonist, which is the most widely used anti-asthma drug worldwide and is classified as a bronchodilator. It has antiinflammatory, and immunomodulatory actions, it also can antagonize flurazepam-induced depression of cerebral cortical neurons.