Pharmaceuticals 2010, 3, 725-747; doi:10.3390/ph3030725 OPEN ACCESS pharmaceuticals ISSN 1424-8247 www.mdpi.com/journal/pharmaceuticals Review Theophylline Peter J. Barnes National Heart and Lung Institute, Imperial College, London, UK; E-Mail:
[email protected]; Tel.: +44-207-351-8174; Fax: +44-207-351-5675. Received: 14 January 2010 / Accepted: 18 March 2010 / Published: 18 March 2010 Abstract: Theophylline (3-methyxanthine) has been used to treat airway diseases for over 70 years. It was originally used as a bronchodilator but the relatively high doses required are associated with frequent side effects, so its use declined as inhaled β2-agonists became more widely used. More recently it has been shown to have anti-inflammatory effects in asthma and COPD at lower concentrations. The molecular mechanism of bronchodilatation is inhibition of phosphodiesterase(PDE)3 and PDE4, but the anti-inflammatory effect may be due to histone deacetylase (HDAC) activation, resulting in switching off of activated inflammatory genes. Through this mechanism theophylline also reverses corticosteroid resistance and this may be of particular value in severe asthma and COPD where HDAC2 activity is markedly reduced. Theophylline is given systemically (orally as slow-release preparations for chronic treatment and intravenously for acute exacerbations of asthma) and blood concentrations are determined mainly by hepatic metabolism, which may be increased or decreased in several diseases and by concomitant drug therapy. Theophylline is now usually used as an add-on therapy in asthma patients not well controlled on inhaled corticosteroids and in COPD patients with severe disease not controlled by bronchodilator therapy.