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Drug Watch - Large volume plastic spacers in asthma

The symptoms of many asthmatic patients are poorly controlled. A recent study from Southampton demonstrated that 51% of patients were waking at night with wheeze, 49% were wheezy at least once a week, 31% had missed school or work in the previous year and 23% were avoiding certain physical activities between attacks.

Ways in which this situation could be improved have been outlined in a paper in the BMJ by Duncan Keeley, an Oxfordshire GP. One of the points he makes is that drugs may not effectively be reaching their site of action in the airways.

Pressurised aerosol inhalers are the mainstay of inhaled treatment for asthma. For a decade there has been the option to prescribe large volume plastic spacers to improve the effectiveness of metered dose inhalers, but their use is still limited.

The main advantage of the spacers is that they increase the proportion of the dose delivered to the airways (where the drugs produce the desired effect), while reducing the proportion absorbed into the body (which is usually the cause of unwanted effects). Metered dose inhalers with large volume spacers deposit at least 30% more drug in the lung but deposit 60% less drug in the patient, because of reduced oropharyngeal deposition.

Specific benefits from the use of large volume spacers include:-
  • More effective treatment with fewer side-effects because of better deposition pattern.
  • Problems of poor inhaler technique largely overcome.
  • Easily used by children and the elderly (except those with weak or arthritic hands).
  • As effective as a nebuliser in treatment of acute attacks but light, cheap, maintenance free, portable and prescribable.
  • Useful for treatment of first attacks of wheezing in patients who have not used inhalers before.
  • Useful for administration of bronchodilator when testing reversibility in the surgery to establish the diagnosis of asthma.
  • Reduced prescribing costs by basing treatment on the much cheaper metered dose inhalers.
As well as the issue of effectiveness, there is also the issue of cost. In England alone in 1991, the costs for salbutamol was £66 million and for beclomethasone £98 million. Both these drugs are now off patent and considerable savings to NHS drug budgets are possible if GPs prescribe these drugs generically. If savings are to be achieved, a number of issues have to be addressed:-
  • GPs need to be confident that generically prescribed salbutamol and beclomethasone inhalers will conform to the colour code blue for bronchodilator and brown for steroid inhalers, and will have inhaler mouthpieces of standard shape to fit the Volumatic spacer devices. Moves towards conformity are in progress through voluntary agreements by the generic manufacturers. Explicit purchasing policies to this effect by regional and district HAs should be considered.
  • HAs will need to publicise to GPs the basis on which they can be confident in the colour coding and mouthpiece shape of generic metered dose inhalers.
  • The continued availability of metered dose inhalers must be assured. They presently use CFC propellants, and adequate stockpiles of CFCs for this purpose must be assured until alternative ozone friendly propellants become available.
  • GPs need information to appreciate the numerous clinical and cost advantages in relying on metered dose inhalers as opposed to the much more expensive dry powder devices.


Keeley BMJ 1992 305: 598-99 Keeley BMJ 1993 307: 1261-63 Jones et al BMJ 1992 304: 361-4 Newman et al Thorax 1984 39: 935-41

Questions to be Answered

Q: What need is met by this device?
A: Significant improvement in treatment of asthmatics, with more effective drug action and reduced side effects, all at reduced cost with generic drugs.
Q: What happens at present?
A: Non-generic drugs predominate. About 30% of total costs are accounted for by dry-powder devices.
Q: Is quality improved?
A: Use of large volume spacers with metered dose inhalers should improve effectiveness of the drugs.
Q: Are large volume spacers prescribable?
A: Yes.
Q: Can cost savings be made?
A: Generic drugs cost less. Change to metered dose inhalers with large volumespacers from dry powder devices would have major cost saving implications.
Q: What is the likely saving cost per million population?
A: As much as £0.5 million per annum per million of population based on a 50% conversion of dry powder to metered dose inhalers and a switch to generic prescribing.

Advice to Purchasers

  • will increase quality and effectiveness.
  • will reduce costs.
  • Research/review would be helpful.
  • include in specification with target for conversion with audit. RCTs also helpful in promotion.

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