A serious side effect of beta blockers is narrowed lung airways in people with asthma (and they already have some narrowing in their airways because of their asthma). Some people with asthma have a clear history of recurrent wheezing attacks (usually beginning in childhood) but some have asthma without knowing it (perhaps because they have none of the typical symptoms and so have not consulted a doctor-and doctors cannot diagnose asthma in people that they have not seen). Any use of beta blockers can be very dangerous for any of these people, however mild their asthma may appear, as even a single dose can cause very severe tightening of the airways (which could be fatal).
Doctors will suspect asthma in anyone who has recurrent episodes of coughing, wheezing, shortness of breath, or chest tightness (all typical symptoms of asthma). Other clues are a history of allergies and asthma affecting other members of the family. Anyone with these symptoms should have their lung function checked to see if they have asthma. This usually involves taking a series of peak flow measurements over a seek or so. Taking these measurements is very simple. All one has to do is to blow as hard and as fast as possible into a small device called a peak flow meter, and the result (the peak flow rate) can be read off its scale. Sometimes this measurement may be taken by the doctor before and after taking some sort of asthma treatment. If the treatment improves a person’s readings then the person definitely has asthma. It is quite essential for everybody to have one peak flow measurement reading before starting on beta blockers. The results can then be compared with expected value for one’s age, sex and height. If one’s reading is 25 percent or more below the suspected value then one should definitely avoid beta blockers and perhaps have more readings to see if one has asthma.
There are two ways in which asthma narrows the airways and causes difficulty with breathing, and two different sorts of inhaler are prescribed to deal with them. The underlying reason is inflammation of the linings of airways, so that they become swollen and produce too much mucus. The inhalers to deal with this contain drugs are known as preventers. The inflammation makes the airways twitch and irritable which means that the spiral muscles which surround them tighten up (spasm) and narrow them still further when one comes across anything that starts one’s coughing or wheezing. The inhalers used during an attack contain drugs known as Relievers.
There are many different reliever inhalers, but perhaps the best known are salbutamol (Aerolin, Ventolin) and tribulation (Brittany). They work by relaxing the spiral muscles, which in turn allows the tightened airways to open up. They generally have a very rapid and easily recognised effect, so people with severe asthma are often tempted to overuse them.
Relievers have little or no effect on blood pressure. However, if one takes too much of them, they can cause disturbances of heart rhythm which can be serious, particularly in people who already have high blood pressure. They are only intended to be used to relieve the asthma symptoms, so they must be used when asthma is causing problems. If there are no symptoms the reliever inhalers should not be used.
Preventive inhalers are designed to be taken regularly, as their purpose is to reduce the underlying inflammation in the airways. There are many different types-but the best known contain corticosteroids such as Beclomethasone dipropionate (Filair, Becotide). Since each dose is concentrated in the lung, preventive inhalers rarely cause significant sodium retention, which in turn means that they rarely cause a rise in blood pressure. This means that there is no reason why one should not take preventive inhalers regularly as prescribed.
The steroid tablets given for very severe asthma attacks are corticosteroids, usually Prednisolone. They may cause some rise in the blood pressure after a few days but even for people with high blood pressure the risks of this are trivial compared with the risks of severe uncontrolled asthma.
Regular inhaler steroids and occasional causes of steroid tablets may often be life-saving for children with severe asthma. Compared with this very real benefit, worries that these treatments may perhaps cause possible high pressure sometime in future are probably trivial.