DRUGS ACTING ON RESPIRATORY SYSTEM
PREPARED BY MR. ABHIJIT DAS
BRONCHODILATORS
DEFINITION
Bronchodilators are medications that help open up and widen the airways in the
lungs, making it easier to breathe.
CLASSIFICATION
1.
Selective Beta-2 Agonists:
Target specific airway receptors, relaxing muscles for better breathing.
Example: salbutamol, terbutaline.
2.
Non-Selective Beta Agonists:
Activate various receptors, aiding airflow but might affect heart. Example: adrenaline,
ephedrine.
3.
Methylxanthines:
Relax airway muscles mildly. Example: theophylline.
4.
Anticholinergics:
Block airway constriction signals. Example: ipratropium bromide.
SALBUTAMOL
MOA
Salbutamol binds to bronchial smooth muscle's beta-2
receptor, activating adenylyl cyclase. This enzyme converts ATP to cAMP,
triggering relaxation of the muscle and causing bronchodilation.
ADVERSE EFFECTS
- Increased
heart rate
- Tremors
- Nervousness
- Headache
- Insomnia
THERAPEUTICAL USES
1.
Asthma:
Salbutamol is commonly used to relieve and prevent asthma symptoms, helping to
open airways and improve breathing.
2.
Chronic Obstructive Pulmonary
Disease (COPD): It's used to manage COPD symptoms by
relaxing airway muscles, making breathing easier.
3.
Bronchospasm:
Salbutamol is also used to treat acute bronchospasms, such as those triggered
by exercise or allergies, to quickly relieve breathing difficulties.
ANTI TUSSIVE AGENTS
DEFINITION
Antitussive agents are medications that help alleviate or suppress coughing,
providing relief from excessive or irritating coughing episodes.
CLASSIFICATION
1.
Opioid Antitussives:
These contain opioids and include medications like codeine and hydrocodone.
2.
Non-Opioid Antitussives:
These do not contain opioids and include medications like dextromethorphan
and benzonatate.
CODEINE
MOA
Codeine binds to the mu receptors in the cough center of the brain's medulla.
By doing so, it deactivates the motor signals responsible for triggering
coughing.
ADVERSE EFFECTS
1.
Sedation
2.
Respiratory depression
3.
Constipation
4.
Nausea and vomiting
5.
Addiction
6.
Tolerance
7.
Withdrawal effects
THERAPEUTICAL USES
1.
Cough Suppression:
Codeine is used to alleviate persistent and bothersome coughing.
2.
Respiratory Conditions:
It can be prescribed for cough associated with respiratory infections or
conditions like bronchitis.
3.
Post-Operative Cough:
Codeine might be given to control coughing after certain surgical procedures.
MUCOLYTIC AGENTS
DEFINITION
Mucolytic agents are
medicines that help thin and loosen mucus in the lungs and airways, making it
easier to cough up and clear.
SOME COMMON CLASSES OF
MUCOLYTIC AGENTS
1.
ACETYLCYSTEINE:
MOA
This medication breaks
down mucus by disrupting its structure (By breaking
down disulfide bonds in the mucoproteins), making it easier to cough up
and clear from the respiratory tract. It's often used in conditions like
chronic obstructive pulmonary disease (COPD) and cystic fibrosis.
NOTE:
Mucoproteins are major components of mucus, contributing to its thick and
sticky nature.
2.
Guaifenesin:
Guaifenesin works by increasing the hydration of mucus,
making it less viscous and easier to expel. It's commonly found in
over-the-counter cough and cold medications.
3.
Erdosteine:
This mucolytic agent not only reduces the viscosity of mucus but also has
antioxidant properties that can help protect the respiratory tract. It's used
to manage conditions like chronic bronchitis.
EXPECTORANTS
DEFINITION
An expectorant is a medication that helps loosen and expel mucus from the respiratory tract,
facilitating easier coughing and clearing of the airways.
CLASSIFICATION WITH MOA
1.
Guaifenesin:
·
Example:
Mucinex (contains guaifenesin)
·
MOA:
Guaifenesin increases the volume and reduces the viscosity of respiratory
secretions, making it easier to cough up and clear mucus.
2.
Ammonium Salts:
·
Example:
Ammonium Chloride
·
MOA:
Ammonium chloride irritates the respiratory tract lining, stimulating secretory
glands to produce more mucus, which can then be cleared more easily.
3.
Iodides:
·
Example:
Potassium Iodide
·
MOA:
Potassium iodide acts as an irritant, causing increased production of
respiratory secretions and helping to loosen and clear mucus.