Asthma: Causes, Pathophysiology, and Treatment

Introduction

Asthma is not curable disease, millions around the world died by asthma because they couldn’t handle it.

Definition : Asthma is a chronic inflammatory disease of the air passage of the lungs. It is characterized by different symptoms, breathlessness, obstruction of airway.

Causes

Asthma occurrence is mainly due to environmental or genetic causes. These causes affect how severe the asthma is and its treatment responsiveness. Before 12 years is mainly due to genetic causes, while onset after 12 is mainly due to environmental causes. There are many triggers that may cause asthma. Bronchial asthma triggers may include: Smoking and passive smoking, Perfumes, Allergens such as” food, dust, drug”, Hard Exercise, Emotional stress and anxiety.

Pathophysiology

Asthma is result of inflammation of the conducting zone(the bronchi and bronchioles) of the airways, which leads to contraction of smooth muscles and narrowing of air passage. The allergen activate immunity system (dendritic cell, mast cell, eosinophil ) which produce hyper-responsiveness and involve other cells like macrophage, cytokine and histamine which lead to swelling, over production of mucus, narrowing of passage and contraction of smooth muscle.

Classification

Asthma is clinically classified according to the recurrence of symptoms, (FEV1), and peak expiratory flow rate. (NIH) decided that each age has its different classification condition.

Management and treatment

There is no typical cure for asthma but only symptomatic treatment. A specific plan for monitoring and managing symptoms should be done. This plan should include decrease exposure to allergens, and the usage of medications. The critical step for asthma treatment is identifying triggers, If trigger avoidance is hard, the medication is a must. Medications for asthma are classified into fast-acting and long-acting categories. Drugs are selected based on the severity of illness and the frequency of symptoms.

Lifestyle modification

Avoidance of triggers is a key component of improving control and preventing attacks. The most common triggers include allergens, smoke (tobacco and other), air pollution, non selective beta-blockers, and sulfite-containing foods. Cigarette smoking and passive smoke may reduce the effectiveness of medications such as corticosteroids, pharmacist and physician should educate patient about how and when use inhaler.

Medications

Medications used to treat asthma are divided into two general classes: fast-relief medications used to treat acute asthma ; and long-term control medications used to chronic asthma.

Drug Used to treat asthma

Formoterol

It is found as: inhaled capsule, MDI and solution for inhalation. It is a long-acting β2 agonist. It is used for chronic asthma but not acute asthma. It is considered as LABA because its onset of action is between (15-30min) and last for >12 hrs while SABA has faster onset but last for 3-4 hrs.

Mechanism of action :Formoterol works like other β2 agonists, it Activate B receptors in lung that make smooth muscle to relax and opens the air tract. B receptors stimulates adenylyl cyclase which is referred to G Protein. AC produces cAMP from ATP. In the lung, cAMP decreases calcium concentrations inside cells. Decreasing intracellular calcium, leads to relaxation of smooth muscle and bronco-dilation.

Budesonide

It is a type of corticosteroid. It is used for treatmenting asthma by inhalation. It is used in chronic asthma and it is also safe in pregnancy.

Mechanism of action: Budesonide is an anti-inflammatory agent that inhibit activity of induced-inflammation cells such as different cytokines, enzymes and adhesion molecules. So it decrease swelling of airway.

Ipratropium bromide

It is used for treating acute asthma. It is found in market as inhaler or nebulizer, it opens the airway in the lung. It mostly used in refractory cases. It is atropine – like structure.

Mechanism of action Ipratropium works as anticholinergic drug which stop and reduce the vagus tone on smooth muscle of lung by competing with acetylcholine at muscarinic receptor, and it is also reduce cGMP formation, which lead to stop increase of intercellular calcium. Thus, it causes relaxation of bronchi.