Salbutamol, The asthma medication that has been found to exceed the permitted limit within Chris Froome’s urine, is not one that we normally associate with undue performance gains.
Salbutamol is most often marketed as Ventolin, and most usually contained within a blue inhaler called a reliever inhaler. It is the most innocuous of asthma treatments and does not require a Therapeutic Use Exemption (TUE) form as it has found to have little or no performance-enhancing effects in athletes unless they are asthmatic.
There is, however, a maximum dosage set out WADA of 800 micrograms per 12 hours, or 1600 micrograms per 24 hours.
This is the limit which Froome is believed to have exceeded – which we will return to later.
Reliever, not enhancer
Salbutamol is part of a group of bronchodilators, which sit below a family of stronger corticosteroid drugs - these include budesonide and usually come in a brown inhaler called a preventer inhaler.
The function of a bronchodilator is purely to alleviate asthmatic symptoms, constriction of the airways, by relaxing the muscles in the lungs and widening the airways.
Salbutamol is usually prescribed without the requirement of any specific tests, but rather any form of breathing trouble or bronchial inflammation will warrant a doctor’s prescription.
Corticosteroids, by contrast, usually require a more serious condition and for use in sport require an ‘asthma provocation test’.
For this the athlete will see a specialist pulmonologist, who does something called flow volume loop testing – a test done at rest and then during exercise to see if there is any demonstrable narrowing of the airways.
Dosage
Pictured here is my own salbutamol inhaler. Assuming Froome has the same inhaler, it delivers 100 micrograms per actuation. The quantity found in his urine was 2000 nanograms per ml.
That would be only 2 micrograms within each ml of urine, but would suggest a dosage of around 16 puffs during a 12 hour period.
Clinically it’s not recommended to take more than 8 puffs in one day, which would be 800 micrograms, and the recommended dosage is 2 puffs - 200 micrograms.
This is partly due to possible side-effects such as increase in heart rate, but also as over-reliance on a preventer inhaler suggests poor control of the condition.
Symptoms requiring such heavy use of an inhaler would suggest the need for elevated treatment – long acting agonists or more potent steroids, for example.
This is most likely the reason why WADA set an upper limit for the drug, to discourage dangerous dosage and poor control of the condition rather than performance enhancements.
Exceeding the limit
Conceivably, an athlete such as Froome may exceed the maximum dosage to alleviate symptoms of an asthma attack more quickly.
When people are admitted to hospital with acute exacerbations of asthma, for example, doctors may give 2500-microgram doses of salbutamol through a nebuliser, 1-2 hourly for the first 24 hours of admittance – a vastly greater quantity than the WADA maximum limit.
That greater dosage does increase the risks of possible side-effects such as tremors and elevated heartrate. There is also much more concerning condition called paradoxical bronchospasm.
This is where the use of salbutamol constricts airflow even more during treatment. These side effects are the reason some athletes side for terbutaline, which is also a bronchodilator but requires a TUE.
As the dosage is released through the actuation of the inhaler, rather than in a pill or liquid form, it’s conceivable for the dosage to be metered incorrectly.
Another unknown in Froome's case is that the microgram dosage he inhaled doesn't necessarily equate to the nanograms of salbutamol in his urine. Some studies have shown that disproportionate spikes in salbutamol levels can occur in the body after inhalation.
This is what was argued by Diego Ulissi during an investigation for an adverse finding of salbutamol in his urine in 2014, and a reason he did not receive a full sanction.