This document discusses antihistamines, which are drugs that reduce or eliminate the effects of histamine released during allergic reactions. Histamine causes symptoms like runny nose and itching. Antihistamines work by blocking histamine from binding to receptors. Common uses include treating allergic rhinitis, conjunctivitis, hives, and insect bites. First generation antihistamines can cause drowsiness while second generation drugs like loratadine are less sedating. Loratadine is prescribed for allergies and hives, with dosages varying based on age. It has the advantage of not causing drowsiness like other antihistamines.

1. Md. Saiful Islam
Executive
PMD & RA
REPHCO Pharmaceuticals Ltd.

2. Antihistamine

3. What is an antihistamine?
 A drug that reduces or eliminates the effects mediated
by the chemical histamine.
 Histamine is released by our body during an allergic
reaction and acts on specific histamine receptors.
 The term antihistamine usually refers to H1 receptor
antagonists.

4. Allergic reaction
 An allergy is an over reaction of the immune system to
a normally harmless substance called allergen.
 Common allergens :
 - pollen
 -animal dander
 -dust
 -mites
 -Chemicals
 -a variety of food

5. Common allergic reactions :
 Include eczema, hives, hay fever, asthma attacks, food
allergies and reactions to the venom of
stinging insects such as wasps and bees.
 Mild allergies like hay fever are highly prevalent in the
human population and cause symptoms such
as allergic conjunctivitis, itchiness and runny nose.

6. Why is this important?
 Allergies are very common in America, 50 million
people suffer from them (about 1 in 4 people)
 Allergies are the 6th leading cause of chronic disease
and they cause the health care system $18 billion
annually
 Over 60% of people with allergies develop asthma as
well
 Keeping them under control is very important!!

7. Clinical Uses of Antihistamines
 Allergic rhinitis (common cold)
 Allergic conjunctivitis (pink eye)
 Allergic dermatological conditions
 Urticaria (hives)
 Angioedema (swelling of the skin)
 Puritus (atopic dermatitis, insect bites)
 Anaphylactic reactions (severe allergies)
 Nausea and vomiting (first generation H1-
antihistamines)
 Sedation (first generation H1-antihistamines)

8. First generation H1 antihistamines:
 Diphenhydramine
 Cyproheptidine
 Promethazine
 Chlorpheniramine
 Hydroxyzine
Classification:

9. • Second generation H1 antihistamines:
 Terfenadine
 Fexofenadine
 Astemizole
 Loratidine
 Desloratidine
 Cetrizine

11. How it works???
 Blocks histamine released by the body to histamine
receptors.
 Histamine produced during allergic reaction.
 Too much histamine coursing through body leads to
fluid release from capillaries.
 By blocking histamine, allergy symptoms alleviated.

14. Dosing information
Usual Adult Dose of Loratadine for Allergic Rhinitis:
 10 mg orally once a day
Usual Adult Dose for Urticaria:
 10 mg orally once a day
Usual Pediatric Dose for Allergic Rhinitis:
 2 to 5 years: 5 mg orally once a day (syrup)
 6 years or older: 10 mg orally once a day (tablets, capsule,
and disintegrating tablets)
Usual Pediatric Dose for Chronic Urticaria:
 2 to 5 years: 5 mg orally once a day (syrup)
 6 years or older: 10 mg orally once a day (tablets, capsule,
and disintegrating tablets)

15. Unique Selling Propositions (USP)
 It has long lasting effects and does not cause drowsiness.
 Cetirizine is said to induce more sleepiness than
Loratadine.
 Cetirizine can also lead to slight breathing difficulties
as one of its side effects.
 According to some studies, Cetirizine is better in
dealing with allergic rhinitis.
 Gives better result in Chronic Urticaria.