20.cough, histamines
TRANSCRIPT
Cough:
Protective reflex caused by stimulation of sensory nerves
in the mucosa of pharynx, larynx, trachea, bronchi induced
by infections, stimulus like smoke, dust etc.
Productive : Associated with sputum.
Nonproductive : Dry cough-No sputum.
Purpose : To expel respiratory secretions.
1. Pharyngeal Demulcents :
Glycerine and liquorice.
Drugs used for cough:
2. Expectorants (Bronchial secretion enhancers ) :
Sodium citrate, potassium citrate, potassium iodide,
Guaiphenesin, vasaka, ammonium chloride
4. Antitussives (cough suppressants) :
Codeine, pholcodeine, noscapine, dextromethorphan
3. Mucolytic :
Bromhexine, Ambroxol,
Acetylcysteine, carbocisteine.
Expectorants
Increase the tracheobronchial gland secretions,
Reduce the viscosity,
Facilitating the removal of sputum.
Used in chronic productive cough
Mucolytics
Break thick tenacious sputum
Lower sputum viscosity
Induce thin copious secretion
sputum comes out easily with less effort
Used in productive cough in chronic bronchitis
Antitussives/ Cough suppressants
In brain - raise the threshold of cough center,
↓cough reflex, suppress cough center in medulla.
In respiratory tract - reduces the tussal impulses.
Used in Dry unproductive cough, cough in allergic states
Severe productive cough – disturb sleep, in hernia/ piles/
cardiac disease/ocular surgery
Histamine :
A chemical present in mast cells, skin, gastric,
intestinal mucosa, lungs etc.
Antihistaminic drugs block H1 receptor and antagonize
the actions of histamine.
Classification
A) First generation antihistamines :
Diphenhydramine, Dimenhydrinate,
Hydroxyzine, Promethazine.
Pheniramine, Cyprohyptadine, Cinnarizine,
Meclizine, Buclizine, Chlopheniramine,
Dimethindene, Tripolidine, Clemastine, Cyclizine
A) Second generation antihistamines :
Cetirizine, Levocetrizine, Azelastine, Mizolastine,
Loratadine, Desloratadine, Rupatadine, Fexophenadine.
Advantages of 2nd generation:
Higher H1 selectivity
No anticholinergic side effects
Don’t cross BBB – no CNS depressant
Don’t impair psychomotor performance in driving
Additional anti-allergic mechanism - ↓↓ histamine release
Limitations of 2nd generation:
Relatively expensive
No anticholinergic – rhinorrhea in cold
No sedation – in severe cough, in child
Uses of antihistamines1.Allergic diseases :
Block the effects of released histamines (pruritus,
urticaria, dermatitis, rhinitis, conjunctivitis) by allergens,
blood transfusion, saline infusion reaction (chills, rigor),
anaphylaxis
2. Insect bite, ivy poisoning and abnormal dermographism
3. Skin: Allergy, Pruritides, urticaria, atopic dermatitis
4. Allergic rhinitis
5. Common cold
6. Cough
7. Seasonal asthma
8.Parkinsonism
9. Vomiting :
Motion sickness, Morning sickness, Postoperative,
Radiation & drug induced vomiting.
10. Vertigo
11.Preanesthetic medication
Adverse effects of antihistaminics:
CNS - Sedation, diminished alertness and concentration,
motor incoordination.
Anti Chol - Dry mouth, blurring vision, constipation,
urinary retention.
Topical application – contact dermatitis.