Antihistamine drugs (Diphenhydramine)

Antihistamine drugs
Introduction
Antihistamines are drugs that treat allergy symptoms by blocking the effects of histamines.
Histamine is chemical released by your body during an allergic reaction and acts on a specific histamine receptor.
There are four types of histamine receptor: H1, H2, H3 and H4 receptors.
The term antihistamine only refers to H1 receptor antagonists.
allergy symptoms:
Congestion, runny nose, sneezing, or itching
Swelling of the nasal passages
Hives and other skin rashes
Itchy, runny eye
Mechanism Of Action
Block action of histamine at H1 receptors.
Compete with histamine for binding at unoccupied receptors.
Cannot push histamine off the receptors if already bound.
Types of Antihistamine
1: first-generation drugs
sedating antihistamine drugs block peripheral H1 receptors, but also cross the blood – brain barrier and block central H1 and cholinergic receptors as well.
Ex. diphenhydramine (Benadryl) - Dimetindene (fenistil)
2: second-generation drugs
Non-sedating antihistamine drugs block peripheral H1 receptors, but do not cross the blood – brain barrier.
Ex. Cetirizine (Zyrtec) - Loratadine (Alavert, Claritin)
Diphenhydramine
Diphenhydramine is in a class of medications called antihistamines
1st generation antihistamine
Has a peripheral and central H1-antagonist action
Sedating antihistamine
Uses
allergic symptoms - insomnia - common cold - Motion sickness
Adverse side effects
Side effects are due to CNS depression :
Sedation - Dizziness - Euphoria - Blurred vision - Tinnitus
Anticholinergic effects
Contraindication
hypersensitivity to diphenhydramine
this drug should not be used in new-born or premature infants
interaction
Alcohol and other CNS depressants
MAO inhibitors

1. Antihistamine drugs Presented by : Dr. Khaled Kouritem

2. Introduction Antihistamines are drugs that treat  allergy symptoms  by blocking the effects of histamines. Histamine is chemical released by your body during an allergic reaction and acts on a specific histamine receptor. There are four types of histamine receptor: H 1 , H 2 , H 3 and H 4 receptors. The term antihistamine only refers to H1 receptor antagonists .

3. allergy symptoms:

4. Mechanism Of Action Block action of histamine at H 1  receptors . Compete with histamine for binding at unoccupied receptors. Cannot push histamine off the receptors if already bound .

5. Types of Antihistamine first-generation drugs sedating antihistamine drugs cross the blood – brain barrier block peripheral & central H 1   receptors Non-sedating antihistamine drugs Not cross the blood – brain barrier block peripheral H 1   receptors Ex. Diphenhydramine ( Benadryl) Dimetindene ( fenistil )

6. Diphenhydramine

7. 1st generation antihistamine H as a peripheral and central H1-antagonist action S edating antihistamine   Diphenhydramine is in a class of medications called antihistamines Brand Names: Benadryl

8. Uses allergic   symptoms pruritus itching common cold Motion sickness   insomnia

9. Adverse side effects Side effects are due to CNS depression : Sedation Dizziness Blurred vision Tinnitus (ringing in the ear) Euphoria Anticholinergic effects

10. Contraindication hypersensitivity to diphenhydramine this drug should not be used in new-born or premature infants interaction Alcohol and other CNS depressants MAO inhibitors

11. Thank you