Question

Explain the major actions of sympathomimetic ,antihistaminic ,corticosteroid decongestants and cromolyn.

Answer 1

These are the drug therapy for Upper Respiratory Diseases

Actions and Uses

1. Antihistamines:

Also known as r H1-receptor antagonists

Examples: Diphenhydramine, Loratadine, Cetirizine, Desloratadine

Mechanism of action: inhibit mast cell degranulation, antagonize histamine receptor-1

They are the drugs of choice for treating allergic rhinitis

Administered orally and distributed systemicall , can reduce the symptoms of nasal itching, sneezing, rhinorrhea, lacrimation, and conjunctival itching

First Generation Antihistamines

1. Alkylamines : Chlorpheniramine maleate,

2. Ethanolamines : Diphenhydramine HCl

3. Ethylenediamines

4. Piperazines : Hydroxyzine HCl

5. Phenothiazines: Promethazine HCl

6. Piperadines: Azatadine

Second Generation Antihistamines

Generally do not cause the sedation and drying seen in first generation antihistamines

Do not cross the blood- rain barrier .

Fexofenadine HCl (Allegra)

Loratadine (Claritin)

Cetirizine (Zyrtec)

Third generation:

Desloratidine

2. Decongestants

They are alpha-adrenergic stimulants that cause vasoconstriction of the nasal mucosa and there by significantly reduces nasal congestion. For allergic rhinitis, decongestants are usually administered along with antihistamines to reduce nasal congestion and they can counteract the sedation caused by many antihistamines.

Example: Phenylephrine, Pseudoephedrine, Naphazoline,

Mechanism of action is by stimulating the α-1 receptors on smooth muscle of nasal blood vessels (causes vasoconstriction).

3. Corticosteroids (Nasal and Lung sprays)

Example : Fluticasone [Flonase]

Mechanism of action:

Reduces the synthesis of inflammatory mediators, decreased infiltration of inflammatory cells, reduce airway edema, mucous production.

Nasal corticosteroid sprays are used to treat upper respiratory infections. Anti-inflammatory lung sprays are used in the treatment and management of asthma.

5. Cromolyn Sodium

Generic name : Cromolyn

Trade names: Apo-Cromolyn, Gastrocrom, NasalCrom

Classification

Therapeutic: anti-asthmatics, allergy, cold, and cough remedies

Pharmacologic: mast cell stabilizers

Pregnancy Category : B

Indications

Inhalation: Prophylaxis (long-term control) of bronchial asthma. Prevention of exercise-induced bronchospasm.

Intranasal: Prevention and treatment of seasonal and perennial allergic rhinitis.

Oral: Mastocytosis. Treatment of food allergy. Treatment of inflammatory bowel disease (IBD).

Action

Cromolyn prevents the release of histamine and slow-reacting substance of anaphylaxis (SRS-A) from sensitized mast cells.

Will decrease frequency and intensity of asthmatic episodes or allergic reactions.