Antiasthmatic Drugs
Asthma is a condition that is characterized by an increased reactivity of the trachea and bronchi to a range of stimuli, showing as airway constriction that changes in severity either spontaneously or as a result of medication. Asthmatic airflow obstruction is caused by three abnormalities:a) Bronchial smooth muscle constriction (bronchoconstriction).
b) Bronchiolar mucosal swelling (bronchial edema).
d) Abnormal bronchial secretions.
Types Of Bronchial Asthma
1. Extrinsic Asthma
It is allergic asthma. It is generally temporary, and it is less prone to Atopic status asthmaticus (immediate because of IgE antibody).
Nonatopic delayed for several hours, linked with precipitating antibody formation
Nonatopic delayed for several hours, linked with precipitating antibody formation
2. Intrinsic Asthma
Status asthmaticus is more common, and it is perennial. COPD is linked to this.
Read More - What is The Management For COPD
Classification Of Antiasthmatic Drugs
Sympathomimetics
β2-agonists are generally frequently used to treat the symptoms of asthma. Epinephrine and ephedrine are structurally linked to the catecholamine norepinephrine, an adrenergic nervous system neurotransmitter. β2-agonists are the preferred medication for treating acute asthma attacks and preventing bronchoconstriction in response to exercise or other stimuli. The β2-agonists have a quick onset of action (within minutes) but are only active for 4 to 6 hours after inhalation.Short Acting: Terbutaline, Salbutamol
Long Acting: Salmeterol, Formeterol, Bambuterol
The drugs used to treat bronchial asthma are explained in terms of their major categories.
Salbutamol is a very highly selective β2-adrenergic stimulant with a significant bronchodilator effect. It is administered orally as well as by nebulizer inhalation. The most common adverse effects of salbutamol include palpitation, restlessness, and anxiousness.
Salmeterol is a novel long-acting selective alpha2 adrenergic agonist with a slow start of action that is used to treat asthma, nocturnal asthma, and exercise-induced asthma.
Mechanism Of Action
When given, beta-2 adrenoceptor agonist binds to beta-2 receptors.1) Adenylate cyclase stimulation
2) Bronchodilation occurs and muscle tone is decreased
3) cAMP levels rise or increased
Methylxanthine
Aminophylline, TheophyllineMethylxanthines (Theophylline and its Derivatives)
Aminophylline is the most often used methylxanthine in the treatment of bronchial asthma. It is a stable theophylline-ethylenediamine combination. These medications inhibit the enzyme phosphodiesterase, resulting in increased intracellular cyclic AMP concentrations. An increase in cAMP causes bronchodilation, heart stimulation, and vasodilation. Caffeine and theobromine are two more significant methylxanthines. Caffeine and theophylline are CNS stimulants that promote alertness and cortical arousal in low doses but cause restlessness, uneasiness, and sleeplessness in large amounts. Methylxanthines stimulate the heart and enhance myocardial contraction force. They relax smooth muscles, particularly the bronchi of asthmatic patients.Mechanism Of Action
1) Inhibit the enzyme phosphodiesterase, which catalyzes the breakdown of cAMP.- Boost cAMP
- Dephosphorylation of MLC
- Bronchodilation
3) Adenosine receptor blockade reduces the contractility of bronchiolar smooth muscles
Anticholinergics: Ipratropium, Oxytropiu, Tiotropium
Anticholinergics, such as atropine and its derivative ipratropium bromide, work by blocking the cholinergic pathways that produce airway constriction. In individuals taking beta2-adrenergic medications for asthma, they may have an additional bronchodilator impact.Mechanism Of Action
1) Muscarinic receptor blockade in the bronchi and bronchioles2) Reduce mucus viscosity
3) Boost mucociliary clearance
Leukotriene Receptor Antagonists
Separate from histamine, leukotrienes released during inflammation are more potent bronchoconstrictor with a longer half-life. Leukotrienes also enhance mucus production, vascular permeability, bronchoconstriction, and bronchial responsiveness. All leukotrienes are produced from the arachidonic acid 5-lipoxygenase pathway and are synthesized by a variety of inflammatory cells in the airways, including eosinophils, mast cells, basophils, and macrophages. Montelukast and zafirlukast are medications used to treat asthmatic individuals.Mechanism Of Action
1) Montelukast and Zafirlukast are antagonistic competitors.2) Reduces bronchospasm and bronchoconstriction by inhibiting the cysteinyl leukotriene Cys LT1 receptor.
3) One medicine, Zileuton, inhibits the physiologic effects of LTC4, LTD4, and LTE4.
4) It also blocks the synthesis of 5 lipoxygenases and is hepatotoxic. Half-life is about 2.5 hours.
Drug Interactions
Zafirleukast interacts with warfarin sodium, causing an increase in prothrombin time; therefore, the dosage must be regulated. Montelukast is a frequently used medication.
Mast Cell Stabilizers
This group's most important members are sodium chromoglycate and ketotifen. They are quite efficient in keeping asthma attacks away. They prevent mast cell degranulation. These medications do not cause bronchodilation and do not counteract the constrictor action of histamine, for example. As a result, they are ineffective in acute asthma occurrences and are only used for prevention. Sodium cromoglycate is delivered as an aerosol rather than orally. Mast cell stabilizers are most commonly used to prevent bronchial asthma, cure nasal congestion, and treat chronic allergic conjunctivitis.- Inhalation of Na chromoglycate
- Nedocromil
- Ketotifen- (5HT action) oral
Mechanism Of Action
1) Block transmembrane Ca influx induced by antigen-antibody interaction on the surface of mast cells. This is a preventative measure that must be taken before the antigen reaches the body.2) Stabilise the membrane of mast cells and prevent the release of chemical mediators
3) Reduce excessive neural responses induced by irritating receptor stimulation
4) Reduce axonal reflexes that cause the release of inflammatory neuropeptides.
5) Prevent cytokine release from T-CELLS
Corticosteroids
Corticosteroids, like mast cell stabilizers, do not directly relax airway smooth muscle but do lower bronchial reactivity, raise airway caliber, inhibit the inflammatory response to antigen-antibody responses or trigger stimuli, and decrease the frequency of asthma exacerbations. They provide longer-lasting symptom alleviation than any bronchodilator or mast cell stabilizer.Different Body Systems-II Systemic steroids are used to treat both severe chronic asthma and acute asthma attacks (status asthmaticus).
Inhaled steroids decrease asthma by acting as a topical anti-inflammatory without creating systemic adverse effects. In asthmatic patients, they reduce bronchial hyperreactivity while increasing the peak expiratory flow rate. They are ineffective during an acute attack or when the patient has status asthmaticus. Sore throat, hoarseness of voice, dysphonia, and oropharyngeal candidiasis are some of the side effects.
Hydrocortisone - IV
Prednisolone - oral
Beclomethasone - inhalation
Budesonide
Flucitasone binds to glucocorticoid receptors in the airways.
Mechanism Of Action
1) Anti-inflammatory properties2) Reduce mucosal oedema, mucus production, and capillary permeability.
3) Mast cell stability
4) Immune response is inhibited, and antibody production is reduced.
5) Histaminergic and cholinergic reactions are inhibited.
6) Improve beta-2 adrenoceptor sensitivity to agonists (Catecholamines)
Ciclesonide
When absorbed medication is acted upon by esterases in bronchial epithelial cells, less drug is attached to glucocorticoid receptors, bones, skin, and eyes, and the probability of osteoporosis and cutaneous thinning is reduced.It plays a function in persons who are prone to cataracts and osteoporosis.
Status Asthmaticus
Status asthmaticus is an acute irritation of asthma that does not respond to bronchodilator therapy. It is a potentially fatal type of asthma since it can induce respiratory failure and cardiac arrest. Status Asthmaticus requires immediate therapy (corticosteroids are required). Air trapping causes fatigue and discomfort in the respiratory muscles. Status asthmaticus is usually accompanied by metabolic acidosis, and acidosis lowers beta agonist potency.1) If the pH is less than 7.5 in a patient with refractory status asthmaticus, IV NaHCo3 is administered, however, there is a danger of hypercapnia in youngsters.
2) PCO2 reduction corrected with nasal/face mask oxygen (Helium)
3) Continuous albuterol nebulization for the first several hours
4) Changed from continuous albuterol to intermittent albuterol every 02 hours. IV
5) Corticosteroids, with ipratropium breathed every 6 hours
Monoclonal Antibodies: Omalizumab
They interact with IgE antibodies found on mast cells. Humanized monoclonal antibodies, whether delivered I/V or subcutaneously, reduce levels of IgE antibodies, reducing the possibility of severe asthma in both stages (immediate or delayed).Treatment For The Control Of Asthmatic Conditions
Various types of treatment may help control asthmatic conditions. The prevention and treatment may involve different types of medicines, advice for changing the lifestyle, and identifying and avoiding the causes of asthma.Many drugs are given for asthma such as Beta-2 agonists, antimuscarinics, corticosteroids, leukotriene inhibitors, and xanthines. These drugs are available in different forms like, inhalers, tablets, capsules, and injections. These drugs are used as per the requirements and medical conditions of the patients.
The drugs used in asthma should be used as per the doctor's prescription as well as advice and also should be purchased from registered pharmacies.
Common Side Effects And Precautions Of Antiasthmatic Drugs
1) Beta2 Agonists
Common side effects such as nervous tension, headache, and muscle cramps may occur.Precautions
It should not be used in patients with cardiovascular disease, hyperthyroidism, arrhythmias, and hypertension.It should be given to diabetic patients with care, and blood glucose should be measured due to the ketoacidosis risk, mainly when beta2 agonists are given through the intravenous route.
2) Antimuscarinics
Common side effects such as cough, headache, dry mouth, and gastrointestinal motility disorder.Read More - Antitussive drugs
Precautions
It should be given carefully to patients with prostatic hyperplasia, and those patients who are susceptible to angle-closure glaucoma.3) Leukotriene Inhibitors
Common side effects such as abdominal pain, headache, thirst, and hyperkinesia in young children.Precautions
Precautions should be taken during pregnancy and breastfeeding.In an acute asthma attack, it should not be used.
4) Corticosteroids
i) Systemic Corticosteroids
Common side effects such as muscle weakness, fragile bone, high blood pressure, diabetes, weight gain, thinning of the skin, glaucoma, and cataracts.Precautions
Paradoxical bronchospasmWith systematic corticosteroid therapy, the initial growth is reduced in children.
ii) Inhaled Corticosteroids
Common side effects like hoarse voice may be developed, and fungal infections of the mouth or throat may occur.Precautions
The height and weight of the children should be measured on an annual basis.The high dose should be avoided due to the adrenal crisis, and coma in children.
5) Xanthines
Common side effects such as nausea, vomiting, diarrhea, gastric irritation, arrhythmias, headache, and insomnia.Precautions
The intravenous, as well as other routes of administration of xanthenes, should be avoided.While used in elderly patients, smokers, and alcoholics, caution should be taken.
For patients with heart failure, viral infections as well as hepatic impairment, it should be used with caution.
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