Cetirizine, A histamine H1 receptor antagonist


Cetirizine

It is a metabolite of hydroxyzine and a selective peripheral histamine H1 receptor antagonist. Cetirizine is a solid crystal from ethanol. The molecular weight of Cetirizine is 388.9g/mol.
The boiling point is 542.1⁰c at 760 mmHg. The melting point is 110-115⁰c. Cetirizine is soluble in water. It is also known as, Ziptek, Zerivate, Xarlin, Benaday, Virlix, Cetirizina, Setir, Cetryn, Humex, Cetirizinum etc.

Structure-

The molecular formula of cetirizine is, [C21H25ClN2O3].


IUPAC name of cetirizine is 2-[2-[(4-chlorophenyl)-phenylmethyl]piperazine-1-yl]ethoxy]acetic acid.

Synthesis-


Mechanism of Action-

It is a metabolite of hydroxyzine, an antihistamine drug. Its main effects are achieved through selective inhibition of peripheral H1 receptors. The antihistamine activity of cetirizine has been shown in a variety of animal and human models.  In vivo and ex vivo animals model have shown insignificant anticholinergic and anti-serotonergic effects. In chemical studies, however, dry mouth is found to be more frequent with cetirizine than with a placebo. In vitro receptor binding studies have demonstrated no detectible affinity of cetirizine for histamine receptors.

Uses -

*Cetirizine is an antihistamine drug that relieves the symptoms of allergies. 
*It is used to treat hay fever, and conjunctivitis (red, itchy eye).
*It is used to treat eczema, hives, and food allergies. 

Doses-

Usual adult dose for allergic rhinitis :

5 to 10 mg orally once a day. 
The maximum dose is 10mg/ day. 
Some experts recommend patients over 65 years of age should be started with 5mg orally once a day.
 
Usual adult dose for urticaria:

5 to 10 mg orally once a day. 
The maximum dose is 10mg/ day. 
Some experts recommend patients over 65 years of age should be started with 5mg orally once a day.
 

Usual pediatric dose for allergic rhinitis:

6 months to 2 years children >

Initial dose-2.5mg orally once a day 
Maintenance dose-2.5mg orally once or twice a day.
Maximum dose-5mg/day.

2 to 5 years old children >

Initial dose-2.5mg orally once a day 
Maintenance dose-2.5mg orally once or twice a day.
Maximum dose-5mg/day.

6 years and older>

5 to 10mg orally once a day. 
Maximum dose-10 mg/day. 

Usual pediatric dose for urticaria:

6 months to 2 years children >

Initial dose-2.5mg orally once a day 
Maintenance dose-2.5mg orally once or twice a day.
Maximum dose-5mg/day.

2 to 5 years old children >

Initial dose-2.5mg orally once a day 
Maintenance dose-2.5mg orally once or twice a day.
Maximum dose-5mg/day.

6 years and older>

5 to 10mg orally once a day. 
Maximum dose-10 mg/day. 

Side effects-

The overdose of cetirizine shows different types of side effects like,
#Feeling sleepy. 
#Tired. 
#Dry mouth.
#Nausea.
#Dizziness. 
#Stomach pain. 
#Diarrhea.
#Sore throat. 

                      ..........THE END..........


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