Asthma drug wrong for some

By MARTIN JOHNSTONE health reporter

Researchers say a common anti-asthma medicine makes the condition worse in patients with a particular genetic make-up.

Salbutamol, an inhaled powder sold under brandnames including Ventolin, is used to relieve asthma and bronchitis.

In an Otago University study, patients received salbutamol, a placebo, or another asthma drug, salmeterol.

The researchers found the 115 patients were of three genetic types, including 16 per cent who were of the "Arg-16" type which they linked to problems with salbutamol.

They checked the number of times patients' symptoms became severely worse after taking medication and found that in the Arg-16 group, the salbutamol patients' rate was twice that of those taking the placebo.

One of the researchers, respiratory physician Associate Professor Robin Taylor, said salbutamol was a useful drug, but should be taken only once or twice a day.

Most asthma should be controlled by preventive drugs.

The researchers were investigating the genetic control of the beta-adrenoceptor protein on the surface of muscle cells lining the lungs.

Salbutamol and other bronchodilator drugs which cause the breathing muscles to relax are aimed at this protein. The drugs bind to the protein, which then signals the muscle cells to relax.

There are 12 different types of the gene that encodes the protein. One of the researchers, from the university's Christchurch Medical School, has developed a $250 blood test to reveal which type a patient has.

The researchers, who addressed the conference of the Australasian Thoracic and Respiratory Science societies in Christchurch yesterday, want to see whether a simple genetic test can be used to guide prescribing bronchodilator drugs.