Dictionary of Allergies .. Aerosol bronchodilators

Beta-adrenergic aerosolised agonists both in metered dose inhaler (MDIs) and solutions are used extensively in the treatment of asthma. The following arguments support the routine use of these agents. 1.  Aerosolized sympathomimetic agents, delivered by a metered dose inhaler (MDI) provide a rapid and effective means of relieving bronchospasm and immediate protection for exercise in a patient with known exercise-induced bronchospasm.  2.  Systemic side effects, such as muscle tremor and palpitations, which are observed when the β2-adrenoceptor stimulant is administered orally or systemically, are minimized.  3.  The efficacy of inhaled β2-adrenoceptor stimulants (e.g. salbutamol, terbutaline etc.) is superior to that of oral agents in blocking exercise-induced asthma.  4.  The dosage needed of a β2-adrenoceptor agonist is a fraction of the oral dose.  5.  The routine use of aerosol β2-adrenoceptor stimulants before inhalation of beclomethazone on cromolyn optimises the opening of small airways enhancing delivery of these medication. The following arguments discourage the routine use of bronchodilating aerosols. 1.  Due to dramatic and rapid bronchodilation some patients may develop psychological dependence on this form of treatment. 2.  Most patients are prescribed a metered dose inhaler (MDI) and are expected to be able to use this device. At least 50% of the patients, however, cannot use a pressurized aerosol if they do not receive further tuition. Errors of coordination are responsible for inefficient use in approximately half the patients and at least as many cannot use a pressurized aerosol because of their inability to inhale after the freon so that drug is released into the mouth (cold freon effect). It has also been shown that over 10% of patients who can use a pressurized aerosol efficiently at one time develop a poor technique with prolonged use (Paterson and Crompton 1976). 3.  They include the potential risk of overuse. 4.  The development of tolerance and tachyphylaxis may be increased. 5.  It has been demonstrated in some animal studies the potential irritative and bronchospastic effects of chlorofluorocarbon propellants. 6.  As long ago as 1957, it was shown that a standard dose of isoprenaline sulphate is effective only when a patient's asthma is mild or moderate and that his dose becomes virtually ineffective when asthma is severe. All patients should, therefore, be aware of the fact that diminished or lack of response to an inhaled bronchodilator means severe asthma, and that at this time, they should take appropriate therapy, seek medical advice or admit themselves to  hospital.

References

Hume, K.M., Gandevia, B.: Forced expiratory volume before and after isoprenaline. Thorax 1957:12:276-8.

Paterson, I.C., Crompton G.K. Use of pressurized aerosols by asthmatic patients. Br. Med. J. 1976;I:76.

Crompton, G.K.: The role of inhaled â„¢-agonists and different delivery systems in asthma. In A New Concept in Inhalation Therapy. ed. by S.P. Newman, F. Moren, G.K. Crompton. Medicom. 1987.

Booker R. Correct use of nebulisers. Nurs Stand. 2007 Oct 31-Nov 6;22(8):39-41.