Salbutamol is a man-made compound derived from the hormone Adrenalin. Salbutamol is a medicine by design; to understand why it is such an effective drug we have to examine its precursor, adrenalin.
Adrenalin (as nearly everyone knows) is the bodies fight and flight hormone, it speeds up heart rate, dilates the bronchioles, speeds nervous transmission, and aerobic respiration, while constricting the gut, dilating the arteries heading to important muscle groups and preparing the body to function at a higher level of efficiency for a short time.
Giving adrenalin to asthma sufferers would solve their immediate problems of breathlessness but lead to more problems later (eg Heart failure). Chemists needed to modify the adrenalin compound so that it only affected bronchiole dilation and nothing else.
By simply adding an alkyl group and combining it with a gaseous delivery method allowed the new compound to fit into the correct receptor sites on the lining of the bronchioles to make them dilate but made it difficult (but not impossible) for the compound to get into the blood stream and affect anything else. However patients, especially children, still get “high” from overusing their inhalers, though this may be due to a sudden increase in the amount of oxygen in their blood.
Salbutamol only works for a short period of time (aprx four hours) because the compound decomposes while it is in the lungs until it no longer fits the receptor site. Preventatives such as Pulmicort inhalers work by using the same principles as the Ventolin but instead of the addition of the alkyl group a long carbon chain is added. This increases the molecules stability in the lungs and increases the longevity of its affect, however it does decrease its efficiency at dilating the bronchioles.
Of course as far as a cure for Asthma goes Salbutamol inhalers and Pulmicort inhalers only manage the symptoms. They do not treat the cause, and so sufferers such as myself are forced to take more and more of them to keep ourselves functioning at a comfortable level. I often have to ask myself if a pharmaceutical company will ever have the incentive to produce a cure for this disease because they are making such a fat profit out of managing my symptoms.