Family doctor

Introduction

The prevalence of asthma is increasing in New Zealand and much of the rest of the world at an alarming rate. Although current asthma therapies, particularly inhaled steroids, have greatly helped to treat patients with asthma, there is a need for new and/or improved medications. Many researchers are currently working on the development of such medications and this article summarises the latest research.

Improvements on existing drugs and devices

There is a worldwide agreement to phase out the production of asthma inhalers containing CFC's over the next few years, due to their adverse effects on the environment. This means that new devices for delivering asthma drugs are being developed.

It is hoped that these new devices, as well as being environmentally friendly, will also be better at delivering asthma drugs to the place where they work - the airways of the lung. Only a small proportion of medicine from current devices gets down as far as the lungs, the rest being deposited in the mouth and throat. Better devices which deliver more drug to the target site will hopefully increase the effectiveness of current drugs.

Many people with asthma use more than one inhaler on a regular basis e.g. use a steroid and drug such as salmeterol (brand name Serevent) twice a day, every day. Several pharmaceutical companies are developing inhalers which contain two drugs. This would make life easier for people with asthma. The drawback with this approach is that such products contain fixed doses of the two drugs, which may not be suitable for everyone.

Preventer drugs, such as inhaled steroids, are usually taken twice a day. However, new research has shown that it may well be possible to get the same effect from taking a higher dose only once a day. Again, this would make life easier for patients with asthma.

Salbutamol (brand names include Ventolin, Airomir, Respolin) is one of the commonest reliever drugs i.e. for the relief of asthma symptoms. Recent work has shown that the drug actually consists of two very similar drugs, or isomers, in equal amounts. Tests show that only one of these isomers relieves symptoms of asthma and the other may actually be bad for asthma. Therefore, work is underway to develop a product containing only the "good" part. It must be emphasised that it is recommended that asthmatics continue to use their salbutamol inhaler as normal.

New drugs

The most promising new drug in development is called "anti-IgE antibody". Many asthmatics react to allergens (particles that can trigger an allergic reaction such as house dust mites and pollens) by producing high levels of a blood protein called IgE. IgE can then start a chain of events leading to an asthma attack. Without IgE, the asthma attack is much less severe, if it occurs at all. The new drug removes excess IgE from the blood and therefore greatly improves the symptoms of asthma.

It is expected that the drug will be available in New Zealand in about two years. Results from early trials have been very promising, with many asthmatic patients able to greatly reduce the amount of steroid they take, or even stop it completely.

During an asthma attack, many chemicals are released and these chemicals are being targeted by new drugs which may help asthma. Targets include IL4, IL5, tryptase, PAF and neurokinin. Unfortunately, these drugs are still at a very early stage of development and it may be several years until a product is released. Anti-IgE is at a much more advanced stage and will be available in the not-too-distant future.

An asthma vaccine

Finally, work is underway here in New Zealand on a potential vaccine which could possibly prevent asthma from occurring in the first place. The vaccine is based on BCG, which is the vaccine used to prevent TB infection.

The basis for this vaccine is the fact that in Westernised countries, where asthma is increasing, we tend to have fewer infections than in the past due to vaccinations, having a more sterile environment and taking antibiotics. This lack of infection is believed to make the immune system more likely to produce allergy and asthma. Therefore, this vaccine may fool the immune system into thinking that infection is present and therefore may prevent the development of asthma. Many trials still need to be done to see if this exciting work will lead to a treatment or even cure for asthma.

Summary

There are many new asthma drugs in development, as well as research into improving current drugs and drug delivery devices. Unfortunately, many of these drugs will not be useful and the useful ones may not be available for some time. However, it is hoped that current and future patients with asthma will have better control of their condition due to the research being carried out.