The asthma drug salbutamol is widely used by athletes, not just to prevent exercise-induced asthma but also for its supposed ergogenic properties. Given orally, this class of drugs, known as Beta-2 agonists, are known to increase muscle mass and the metabolism of lipids and carbohydrates, as well as exerting antidepressant effects on the central nervous system.

However, new French research suggests that those who inhale salbutamol in search of such effects are wasting their time and money. A study of the effects of two doses of inhaled salbutamol compared with placebo in 12 trained non-asthmatic triathletes failed to demonstrate a significant effect on endurance performance.

Each subject performed three identical exercise sessions on a cycle ergometer at 85% of their predetermined maximal aerobic power until exhaustion. One session was performed after inhalation of 200µg of salbutamol, another after an 800µg dose and a third after inhalation of placebo - the main criterion for an ergogenic effect being an increase in endurance time.

In fact, maximal endurance times proved similar under each of the three conditions. Moreover salbutamol had no significant effects on plasma levels of glucose and lipids or on central nervous system function.

However, the researchers point out that their results do not preclude an ergogenic effect of Beta-2 agonists given by other routes or over longer periods. They note that levels of the higher dose drug in urine four hours after exercise was very low and that the smaller doses typically prescribed for asthma would probably result in negative urine tests if inhaled during competition.

However Beta-2 agonists are the drugs mostly commonly identified by urine tests during sports competitions, particularly bicycle races.

'We believe... that most non-asthmatic salbutamol users take the drug orally or by injection, probably for protracted periods,' conclude the researchers. 'This pattern of use may be associated with ergogenic and metabolic effects.'

Thorax 2001 Sep 56(9), pp675-9

Isabel Walker