Salmeterol
There are a number of alternative bronchodilators now commonly available. The most common of these is salmeterol, shown below, an analogue of salbutamol.
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Salmeterol |
Salmeterol has an effective duration that last over twice as long as salbutamol, whilst also being highly beta2 selective. In addition, in similar doses salmeterol provides a much more powerful bronchodilation effect. However, salmeterol is a slower-acting drug than salbutamol.
Another longer lasting, selective beta2 receptor agonist is formoterol. Whilst having a similar duration period as salmeterol, formoterol acts faster, and has been found to be a more cost-effective therapy than salmetrol treatment.
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Formoterol |
There are also a number of older bronchodilators available, such as terbutaline. Whilst being a potent bronchodilator, terbutaline also stimulates beta1 receptors, leading to side effects such as tremors, increased heart rate, central nervous system stimulation, and headaches. Other side effects include peripheral vasodilation, hypokalaemia, urticaria, paradoxical bronchospasm, angio-edema, and a number of serious cardiac effects. These serious side-effects have limited its popularity.
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Terbutaline |
Also in general usage is the drug pirbuterol, which again acts in a similar manner to salbutamol, being a beta2 adrenoceptor agonist.
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Pirbuterol |
Another class of bronchodilators are Xanthine drugs, such as theophylline and enprofylline. Although there exact mechanism of action has yet to be identified, it is know that they do not stimulate adrenoceptors. However, they have many other adverse pharmacological effects such as cardiovascular, gastrointestinal and central nervous system problems. In the USA, xanthine drugs are used as a front line drug, but in the UK their usage is highly controversial.
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Theophylline |
Enprofylline |
The final class of commonly used bronchodilators are muscarinic-receptor antagonists, such as ipratropium bromide. This helps in asthma cases by inhibiting bronchospasm. It is normally used together with another bronchodilator such as salbutamol.
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Ipratropium bromide |