Bronchodilators Research Paper

Bronchodilators are important in the treatment of airways disorders such as chronic obstructive pulmonary disease (COPD) and asthma and critical in the management of the disorders symptoms. There are 3 major classes of bronchodilators currently in use, namely xanthines, β2- adrenoceptor agonists and muscarinic receptor antagonists (2). Examples of drugs which fall into these classes are discussed later. They can be taken on their own or in combination. The relaxation/contraction of smooth muscle cells of the airways are influenced by the autonomic nervous system, the sympathetic nervous system and the parasympathetic nervous system. Activation of the sympathetic nervous system causes release of noradrenaline. Noradrenaline release on smooth
They increase cAMP levels by inhibiting the enzyme phosphodiesterase (PDE). This enzyme functions is to break down cAMP. (3). Increased cAMP in smooth muscles results in relaxation. This is because cAMP inhibits an enzyme (myosin light chain kinase) that phosphorylates smooth muscle myosin which causes contraction (4). They are also adenosine antagonists (8). Therapeutic uses of xanthines include: mild cases of asthma, an adjunct in COPD, chronic bronchitis. Side effects of xanthines include: nausea, anorexia and increased urination. Theophylline is an example of a xanthine
They are a member of a seven transmembrane spanning family of GPCRs (2). Activation of these receptors in the lungs results in bronchodilation. The binding of β2 agonists to β2 receptors activates cAMP. cAMP levels increases, resulting in the increased activity of the enzyme protein kinase A (PKA) , causing phosphorylation of for example myosin light chain. The activation of β-2 receptors leads to inhibition of phosphoisonitol hydrolysis, a drop in calcium levels intracellularly, and the activation of k+ channels. Results in relaxation of airway smooth muscle (2). This causes relaxation of smooth muscles of the airway, bronchial dilation and increased airflow (3) (5). Used most commonly to treat asthma (both acute and chronic) and COPD (6). Other uses include hypotension and shock and hyperkalaemia (3). Some examples of β2 agonists include salbutamol, which is a short-acting selective β2 agonist (7), formoterol, and isoproterenol (isoprenaline), which is a β non-selective agonist (3). Isoprenaline as a result of being non-selective, has adverse effects as it activates β-1 adrenoceptors in the heart, causing tachycardia