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Cetirizine; Uses, Dosage, Side Effects, Drug Interactions

Cetirizine is a potent second-generation histamine H1 antagonist that is effective in the treatment of allergic rhinitis, chronic urticaria, and pollen-induced asthma. Unlike many traditional antihistamines, it does not cause drowsiness or anticholinergic side effects.

Cetirizine is a metabolite of hydroxyzine and a selective peripheral histamine H1-receptor antagonist. It is used for symptomatic treatment of seasonal and perennial allergic rhinitis and for chronic urticaria.

Cetirizine and its enantiomer levocetirizine are second-generation antihistamines that are used for the treatment of allergic rhinitis, angioedema, and chronic urticaria. Cetirizine and levocetirizine have been linked to rare, isolated instances of clinically apparent acute liver injury.

Cetirizine is a potent second-generation histamine H1 antagonist that is effective in the treatment of allergic rhinitis, chronic urticaria, and pollen-induced asthma. Unlike many traditional antihistamines, it does not cause drowsiness or anticholinergic side effects. Second-generation antihistamines like cetirizine are less able to cross the blood-brain barrier and therefore have diminished effects on the central nervous system compared to first-generation drugs. As such, they are less likely to cause drowsiness or memory impairment.

Mechanism of action of Cetirizine

Cetirizine competes with histamine for binding at H₁-receptor sites on the effector cell surface, resulting in suppression of histaminic edema, flare, and pruritus. The low incidence of sedation can be attributed to reduced penetration of cetirizine into the CNS as a result of the less lipophilic carboxyl group on the ethylamine side chain.Cetirizine acts as a highly selective antagonist of the histamine H₁ receptor.The K_i values for the H₁ receptor are approximately 6 nM for cetirizine, 3 nM for levocetirizine, and 100 nM for dextrocetirizine, indicating that the levorotatory enantiomer is the main active form. Cetirizine has 600-fold or greater selectivity for the H₁ receptor over a wide variety of other sites, including muscarinic acetylcholine, serotonin, dopamine, and α-adrenergic receptors among many others.The drug shows 20,000-fold or greater selectivity for the H₁ receptor over the five muscarinic acetylcholine receptors and hence does not exhibit anticholinergic effects. It shows negligible inhibition of the hERG channel (IC50 > 30 µM)and no cardiotoxicity has been observed with cetirizine at doses of up to 60 mg/day, six times the normal recommended dose and the highest dose of cetirizine that has been studied in healthy subjects.

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Indications of Cetirizine

Chronic Idiopathic Urticaria
Perennial Allergic Rhinitis (PAR)
Pollen Allergy
Sneezing
Runny nose
Itchy or watery eyes
Itchy throat or nose
Upper respiratory tract hypersensitivity reaction, site unspecified
Rhinorrhea
Postnasal discharge,
Nasal pruritus,
Ocular pruritus &tearing
Cetirizine is indicated for the relief of nasal and ocular symptoms of seasonal and perennial allergic rhinitis.
Cetirizine is indicated for the relief of symptoms of chronic idio
For the relief of symptoms associated with seasonal allergic rhinitis, perennial allergic rhinitis and the treatment of the uncomplicated skin manifestations of chronic idiopathic urticaria

Contra-Indications of Cetirizine

Increased Pressure in eyes
Liver problems
Kidney disease with a reduction in kidney function
Cannot Empty Bladder

Allergies

Antihistamines
Antihistamines – Piperazine

Dosage of Cetirizine

Strengths: 10 mg; 5 mg; 1 mg/mL

Children aged 6 to 12 years

The recommended dose is 5 mg twice daily as half a tablet twice a day.

Adults and children aged 12 years and over

The recommended dose is 10 mg once daily as one tablet.

Allergic Rhinitis

5 to 10 mg orally once a day
Maximum dose: 10 mg/day

Urticaria

5 to 10 mg orally once a day
Maximum dose: 10 mg/day

Pediatric Dose

Allergic Rhinitis

6 months to 2 years

Initial dose: 2.5 mg orally once a day
Maintenance dose: 2.5 mg orally once to 2 times a day
Maximum dose: 5 mg/day

2 to 5 years

Initial dose: 2.5 mg orally once a day
Maintenance dose: 2.5 mg orally 2 times a day OR 5 mg orally once a day
Maximum dose: 5 mg/day
6 years and older: 5 to 10 mg orally once a day
Maximum dose: 10 mg/day

Urticaria

6 months to 2 years

Initial dose: 2.5 mg orally once a day
Maintenance dose: 2.5 mg orally once to 2 times a day
Maximum dose: 5 mg/day

2 to 5 years

Initial dose: 2.5 mg orally once a day
Maintenance dose: 2.5 mg orally 2 times a day OR 5 mg orally once a day
Maximum dose: 5 mg/day
6 years and older: 5 to 10 mg orally once a day
Maximum dose: 10 mg/day

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Side Effects of Cetirizine

The most common

headache,
drowsiness,
fatigue and
dry mouth.
Sleepiness
Tiredness
Stomach pain
Headache
Diarrhea
An opposite reaction in which you feel excited, jittery, or nervous, known as paradoxical CNS stimulation instead of drowsy or sleepy

More common

headache
fast, pounding, or uneven heartbeat;
fever, flu symptoms;
seizure (convulsions); or
jaundice (yellowing of the skin or eyes).
dry mouth, sore throat, cough;
muscle pain;
drowsiness, tired feeling;
nausea,
fever, flu symptoms;
seizure (convulsions); or
jaundice (yellowing of the skin or eyes).

Less common

Dizziness
dry mouth
dysmenorrhea, such as, difficult or painful menstruation
dyspepsia, such as, acid or sour stomach, belching, heartburn, indigestion, stomach discomfort , upset or pain,
fatigue, such as, weakness
myalgia, such as, joint pain, swollen joints, muscle aching or cramping, muscle pains or stiffness, difficulty in moving
pharyngitis, such as, body aches or pain, congestion, cough, dryness or soreness of throat, fever, hoarseness, runny nose, tender swollen glands in neck, trouble in swallowing, voice changes.
somnolence, such as, sleepiness or unusual drowsiness
nausea
liver damage or inflammation
tightness in the chest or breathing tube
passing out or fainting
seizures

Drug Interactions of Cetirizine

Cetirizine may interact with following drugs,supplements & may change the efficacy of drugs

other antihistamines (e.g., diphenhydramine, chlorpheniramine, hydroxyzine)
antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
aripiprazole
atorvastatin
atropine
azelastine
“azole” antifungals (e.g., fluconazole, ketoconazole, voriconazole)
baclofen
barbiturates (e.g., butalbital, pentobarbital, phenobarbital)
benzodiazepines (e.g., lorazepam, diazepam)
brimonidine
buprenorphine
buspirone
carvedilol
cyclosporine
dexamethasone
ipratropium
ketotifen
mirabegron
propranolol
seizure medications (e.g., clobazam, , phenobarbital, phenytoin, valproic acid, zonisamide)
selective serotonin reuptake inhibitors (SSRIs; e.g., citalopram, duloxetine, fluoxetine, paroxetine, sertraline)
tapentadol
thiazide diuretics (water pills; e.g., hydrochlorothiazide, indapamide, metolazone)
tiotropium
tolterodine
tramadol
tranylcypromine
tricyclic antidepressants (e.g., amitriptyline, clomipramine, desipramine, trimipramine)
tyrosine kinase inhibitors (e.g., dabrafenib, imatinib, nilotinib, sunitinib)
verapamil

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Pregnancy & Lactation of Cetirizine

FDA Pregnancy Category C

Pregnancy

This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Lactation

It is not known if cetirizine passes into breast milk. If you are a breastfeeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breastfeeding.