Monitoring of Theophylline Treatment

Theophylline is a potent xanthine derivative used as a barometrically in the treatment of asthma and chronic obstructive pulmonary disease (COPD). The drug has a very narrow therapeutic margin; Therapeutic plasma concentrations range from 10 to 20 ug/mL with severe toxicities associated with higher concentrations. Fortunately, however, the therapeutic efficacy and also untoward effects of theophylline is closely related to its concentration in the vascular system. Hence, the concept of 'therapeutic drug monitoring' has been applied to therapy with this drug with astonishing success.

Pharmacokinetics of theophylline has been studied extensively and several dosing guidelines have been suggested.

Theophylline and its derivatives are available as oral preparations and injectable solutions. Oral preparations contained either theophylline or aminophylline while injectable solutions usually contain aminophylline (equivalent to 0.8 of theophylline). Oral preparation of theophylline are available as regular or controlled release formulations.

Absorption

Distribution

Theophylline distribute very rapidly into the peripheral tissues. Therefore, the loading dose should be given based on total body weight.

Elimination

Theophylline is extensively metabolized to inactive metabolites. Many factors such as age, smoking, disease state and presence of other drugs may interfere with clearance of the drug.