In finding the treatment of asthma, more than hundred years of research has been put into the development of introducing the right agent triggering a specific response; Salbutamol as a ventolin inhaler, a ? 2-adrenoceptor agonist. This research report addresses the main compound that was considered as a “hit” in reversing the airway obstruction and why other compounds such as epinephrine and isoprenaline were neglected over salbutamol. A compound known as epinephrine in adrenaline injection was first addressed for the treatment of asthma in 1903 by Bullowa & Kaplan.
Few years later its usage soon came to an end when it had been found to cause unwanted effects on cardiovascular system. After numerous tests and development, in 1940 Konzett identified isoprenaline; a remedy which replaced adrenaline. The effect on treating airway obstruction was promising however like the epinephrine effect on cardiovascular system was still seen. Salbutamol was then introduced by Allen & Hanburys in 1969, which is currently the most suited remedy for asthma. They are highly effective, had much longer duration than the previous drugs and had little or no cardiovascular side effects. It was the subdivision of ? -receptors into 2 ? 1 (cardiac muscle) and ? 2 (bronchial smooth muscle) that allowed salbutamol inhaler to be developed (Lands et al. , 1967. By understanding the existence of these subdivisions, salbutamol was made with more selectivity on ? 2 receptor and hence showing hardly any side effects on cardiovascular system.
Tests to show the specificity of salbutamol have been conducted on an isolated guinea pig, salbutamol showed 1/10 activity of adrenaline on trachea and 1/2000 activity on atria (Cullum et al., 1969). Isoprenaline and epinephrine were neglected over salbutamol since they are both ? 1 and ? 2 non-selective agent, they activate the ? 2-adrenoceptors and they would also non-selectively activate the ? 1-adrenergic receptor causing problems in cardiovascular system. In the past several experiments have been conducted to find an efficient way to use isoprenaline. Such experiment includes; altering its intake concentration, as concentration got lower the effect on ?
1-adrenogenic had lowered as well as the duration and vice versa (Alliott et al. , 1972). Combining ? 1-adrenergic receptor antagonist (propranolol) with isoprenaline, researchers depended on the effect of propranolol possibly binding to the ? 1 receptor blocking its activation, which could possibly maintain the stable conditions of the heart. This in fact gave a negative outcome since propranolol is also a non-selective agent therefore blocking the ? 2 receptor, reducing the effect of isoprenaline (Maclagan et al. , 1979). Improving these remedy with other mixture and change in concentration of the compound would have no effect due to the chemical structure as the isopropyl amine group (in epinephrine and isoprenaline) caused the agent to be selective for ? receptors. It required the tertiary butyl group existent in salbutamol for the compound to be ? 2 selective agent (Brittain et al. , 1968).
Over hundred years of combined understandings of medicinal chemistry and receptor biology, from the lead compound Adrenaline, Salbutamol has been introduced as Ventolin in treating asthma. Even though Ventolin is currently the worlds most approved remedy, there are studies in which tries to develop Ventolin into a better product, such research includes; extending its duration and also become more efficient even after a severe asthma attack, showing that this development in research to treat asthma is still running to show much more improvement in the future.
REFERENCE
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