13dimethylxanthine

Theophylline, also known as 1,3-dimethylxanthine or 13-dimethylxanthine, is a methylxanthine alkaloid derived from xanthine. It is used medically as a bronchodilator and is structurally related to caffeine and theobromine.

Theophylline exerts bronchodilation primarily by nonselective inhibition of phosphodiesterases, which increases intracellular cAMP in bronchial smooth muscle, and by antagonizing adenosine receptors, reducing bronchial constriction. It also has mild diuretic and central nervous system stimulant effects.

Theophylline has been used to treat symptoms of asthma, chronic obstructive pulmonary disease, and, in some cases, apnea of prematurity. Because of a narrow therapeutic window and potential toxicity, dosing is individualized and often monitored by serum levels; many guidelines favor inhaled bronchodilators rather than theophylline where possible.

It is well absorbed after oral administration and is mainly metabolized in the liver by cytochrome P450 enzymes, notably CYP1A2. The elimination half-life varies with age and factors such as smoking. Drug interactions from antibiotics like macrolides and fluoroquinolones, as well as with agents such as cimetidine, cholestyramine, and certain anticonvulsants, can alter theophylline levels.

Common adverse effects include nausea, vomiting, tachycardia, palpitations, insomnia, and in severe cases seizures and arrhythmias. Toxicity is dose-related; monitoring and dose adjustment are important, particularly in children, the elderly, and those with liver disease.