Bronchial Asthma Treatment - NEET PG Pharmacology

Bronchial Asthma is a chronic inflammatory airways disorder which manifests itself as recurrent episodews of breathlessness, wheezing, cough and chest tightness.

This blog will throw light on the Bronchial Asthma treatment and will further help you to upgrade your NEET PG preparation. 

Let’s get started with the drugs used for the treatment of Asthma. 

There are four kinds of bronchial asthma drugs used for the Bronchial Asthma Treatment. They are:

• Bronchodilators
• Drugs that can decrease leukotrienes (LT).
• Drugs that can stabilize the mast cell.
• Drugs that can stop the antigen-antibody reaction.

1. Bronchodilators                                                                            

• There are 3 types of bronchodilators

1. β₂ agonists
2. M₃ blockers/anti-cholinergic
3. Phosphodiesterase like inhibitors

1. β₂ agonists
   • There are 2 kinds of beta 2 agonists like:
     • Short acting beta 2 agonists (SABA): salbutamol and terbutaline.
     • Long-acting beta 2 agonists (LABA): Salmeterol and formoterol. 
   • SABA- Are used for acute asthma.
   • LABA- Used for prophylaxis of asthma. But formoterol can be used for acute attack as well. Salmeterol is slow acting. Hence, can only be used for the prophylaxis of asthma.
   • Side Effects
     • T - Tremors (Most common side effect of β₂ agonists).
     • T - Tachycardia
     • T - Tolerance
     • T - T-wave changes in ECG due to hypokalemia.
   • According to GINA guidelines, the DOC to prevent and treat the attack is a combination of salmeterol and Inhaled corticosteroids (ICS).
2. M₃ blockers/anti-cholinergic drugs
   • Drugs in this category include:
     • Ipratropium
       •  Can be administered through inhalational route. 
       • Some people develop paradoxical bronchoconstriction with ipratropium.
       • The reason may be the fact that there may be impurities in the ipratropium like benzalkonium/EDTA, hypertonic saline when used in the nebulizers which can irritate the respiratory pathway and they may block the muscarinic receptors which will increase the level if Ach.
     • Tiotropium 
3. Phosphodiesterase inhibitor
   • Drugs in this category include
     • Theophylline 
     • Aminophylline
   • These drugs cannot be given through inhalational routes. Hence, they are administered either orally or as I/V.
   • These are also adenosine 1 receptor antagonists apart from being phosphodiesterase inhibitors.
   • SIDE EFFECTS (PDE antagonism):
     • Arrhythmias
     • GI side effects like nausea and vomiting.
   • Side Effects (Adenosine receptor antagonism)
     • Arrhythmias
     • Diuresis
     • Epileptic seizures
   • Theophylline
     • It is metabolized by microsomal enzymes.
     • Its efficacy will be decreased by enzyme inducers like rifampicin and through smoking.
     • Whereas, enzyme inhibitors like ciprofloxacin and erythromycin can inhibit the metabolism which can lead to toxicity.
     • At the toxic doses, they can stimulate the heart and the brain which can lead to tachycardia, seizures etc.

2. Drugs that can decrease leukotrienes (LT)                                       
   • Formation of LT
     • Arachidonic acid is produced by the phospholipids in the membrane with the help of with the help of the enzyme phospholipase A₂ (PLPA₂). 
     • The arachidonic acid may be converted into prostaglandin by COX or leukotrienes by LOX.
     • Leukotrienes work on the LT receptors which will lead to bronchoconstriction. 
     • Action of leukotrienes can be decreased by the following methods:
       • By Inhibiting the action of PLPA_2.
       • By inhibiting LOX
       • By blocking LT receptors.
     • The drug inhibiting PLPA2₂ are steroids. 
       • Steroids are not bronchodilators.
       •  But they can be used in the case of an acute asthma attack because of their anti-inflammatory effect and also because of the fact that they increase the sensitivity of the bronchus to β₂ receptors. 
       • In such a condition, a drug like salbutamol can work better. 
     • The drug inhibiting LOX is zileuton.
     • The drugs acting as leukotriene receptor antagonists are zafirlukast and montelukast.
3. Mast cell stabilizers 
   • Drugs which help to stabilize mast cells are:
     • Nedocromil
     • Ketotifen
   • These drugs are used only for the prophylaxes of asthma.
   • They cannot be used for the treatment of acute asthma as they are not effective enough.
4. Drugs against IgE
   • Drug in this category is omalizumab.
   • It is administered subcutaneously.
   • When asthmatic attack cannot be prevented by other drugs, omalizumab is administered. 

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