Bronchial asthma is characterised by hyper responsiveness of tracheo-bronchial smooth muscle to a variety of stimuli, resulting in narrowing of air tubes, often accompanied by increased secretion and mucosal edema. Extrinsic asthma : It is mostly episodic, less prone to status asthmaticus. In others, a variety of trigger factors (infections, irritants, pollution, exercise, exposure to cold air, psychogenic) may be involved. Intrinsic asthma : It tends to be perennial, status asthmaticus is more common. Most cells present in lungs release mediators (histamine, SRS-A etc) leading to constriction of bronchial smooth muscle, cause mucosal edema and viscid secretion resulting in reversible airway obstruction. Bronchodilators : A. sympathomimetics : Adrenaline, Ephedrine, Isoprenaline, Orciprenaline, Salbutamol, Terbutaline. B. Methylxanthines : Theophylline (anhydrous), Aminophylline, Choline theophyllinate, Hydroxyethyl theophylline, Theophylline ethanolate of piperazine. C. Anticholinergics : Atropine methonitrate, Iprotropium bromide. Mast cell stabilizers: Sodium Cromoglycate, Ketotifen. Corticosteroids : A. sstemic : Hydrocortisone, Prednisolone and others. B. Inhalational : Beclomethasone dipropionate. Miscellaneous : Antihistamines : Mepyramine and congeners.
