Bronchodilators: beta 2 agonists versus theophylline.

Beta 2 agonists are best administered by inhalation since this route provides maximum therapeutic effect with minimum side effects. Plasma levels are lower and muscle cramps, tachycardia and tremor less common. Inhalation may be carried out by use pressurised inhalers (with various modification if necessary), by a Rotahaler with Salbutamol powder, and by nebulisers. All have their uses. Apart from their immediate bronchodilator effect, it is customary to give Beta 2-agonists routinely before inhalation beclomethasone, and there is evidence that regular use of Beta 1-agonists has a useful suppressive effect. In severe chronic asthma high doses may be indicated and be effective where conventional doses have failed. The introduction of reliable sustained-release preparation of theophylline and its derivatives together with plasma assays theophylline levels has enabled therapy to be optimal and side effects to be lessened. The therapeutic range is a plasma concentration of 10-20 mg/l. There are large individual variations in hepatic clearance of theophylline, which may also be influenced by age, liver disease, drugs and viral infections. Theophyllines are less effective as bronchodilators than Beta 2-agonists but in chronic severe asthma have a place for their additive effect. They are used most frequently to suppress nocturnal asthma and early morning wheezing.