New aspects of the therapeutic potential of theophylline in asthma.

In addition to its bronchodilating activity, the antiasthmatic drug theophylline also reduces microvascular permeability and increases mucociliary clearance, diaphragmatic contractility, and circulating catecholamine levels. Both experimental and clinical data now suggest that at therapeutic serum levels, theophylline is also of value during the delayed asthmatic reaction by inhibiting airway inflammation and the associated bronchial responsiveness. In vitro, high theophylline concentrations inhibit histamine release from mast cells and basophils. This drug also suppresses polymorphonuclear leukocyte activation and stabilizes a variety of inflammatory cells at therapeutically relevant concentrations.