Cetirizine

Cetirizine is a second-generation antihistamine medication that is commonly used to treat allergy symptoms such as hay fever, hives, and allergic conjunctivitis. It works by blocking the effects of histamine, a substance released by the body during an allergic reaction that causes symptoms such as itching, sneezing, and runny nose.

Cetirizine is used in the treatment of Allergic rhinitis and Urticaria.

Cetirizine is rapidly and well absorbed from the gastrointestinal tract after oral administration. It reaches peak plasma concentrations within 1-2 hours of ingestion. Cetirizine is widely distributed throughout the body, with a volume of distribution of approximately 0.5 L/kg. It is highly bound to plasma proteins (93-98%), and does not readily cross the blood-brain barrier, which contributes to its low sedative effects. Cetirizine is minimally metabolized in the liver, with less than 14% of the drug undergoing hepatic metabolism. The majority of the drug is eliminated unchanged in the urine. Cetirizine is primarily excreted in the urine, with approximately 70% of the drug being eliminated unchanged. The remainder of the drug is eliminated in the feces.

Tmax is approximately 1-2 hours after administration.

Cmax of Cetirizine after a single oral dose 300-400 ng/mL.

Cetirizine shows common side effects like Drowsiness or tiredness, Dry mouth, Headache, Nausea, Dizziness, Sore throat, Abdominal pain, Diarrhea and Vomiting .

Cetirizine is available in tablets, oral solutions and syrup

Cetirizine is available in India, Germany, Canada, France.

Cetirizine is a H1 receptor antagonist, Cetirizine binds to and blocks the histamine H1 receptors located on cells in the body that are responsible for mediating the allergic response, such as the cells in the eyes and nose. By blocking these receptors, Cetirizine can reduce the symptoms of allergic reactions, including itching, redness, and swelling.

Oral: Administer with water 1 hour before or 2 hours after intake of food or fruit juices.

Cetirizine is used in the treatment of Allergic rhinitis and Urticaria.

Cetirizine is a second-generation antihistamine medication that is commonly used to treat allergy symptoms such as hay fever, hives, and allergic conjunctivitis. It works by blocking the effects of histamine, a substance released by the body during an allergic reaction that causes symptoms such as itching, sneezing, and runny nose.

Cetirizine is an antihistamine medication that is commonly used to treat the symptoms associated with allergies, such as:

Oral:

Allergic rhinitis: Relief of symptoms associated with allergic rhinitis.

Urticaria, chronic spontaneous: Treatment of uncomplicated skin manifestations of chronic spontaneous urticaria.

Injection:

Urticaria, new onset: Treatment of new-onset (acute) urticaria.

Although not approved there have been certain off label use documented for Cetirizine which includes:

Anaphylaxis (adjunct to epinephrine for relief of cutaneous symptoms); Angioedema, acute allergic or recurrent idiopathic; Infusion reaction, premedication

Nasal

Seasonal allergic rhinitis

Adult: As 0.6% spray: 2 sprays into each nostril bid.

Child: 6-11 year 1 spray into each nostril bid.

Ophthalmic

Allergic conjunctivitis

Adult: As 0.1% soln: 1 drop in the affected eye(s) bid at an interval of 6-8 hr. As 0.2% soln: 1 drop in the affected eye(s) once daily.

Child: ≥3 yr Same as adult dose.

Cetirizine is available in the dosage strength of

• Tablets: 5 and 10 mg
• Oral solution: 1mg/ml and 5mg/ml

Cetirizine is available in the form of tablets, solutions and syrup.

• Dosage Adjustment in Kidney Patient

CrCl >31 mL/minute: No dosage adjustment necessary.

CrCl 11 to ≤31 mL/minute: 1 tablet (cetirizine 5 mg/pseudoephedrine 120 mg) once daily.

CrCl ≤10 mL/minute: There are no dosage adjustments provided in the manufacturer's labeling.

Hemodialysis (cetirizine <10% dialyzable): 1 tablet (cetirizine 5 mg/pseudoephedrine 120 mg) once daily.

• Dosage Adjustment in Hepatic impairment Patient

Mild to severe impairment: 1 tablet (cetirizine 5 mg/pseudoephedrine 120 mg) once daily.

• Dosage Adjustment for Pediatric Patients

Altered kidney function (Zyrtec D prescribing information 2003):

Children ≥12 years and Adolescents: Oral: Cetirizine 5 mg/pseudoephedrine 120 mg per tablet:

CrCl >31 mL/minute/1.73 m2: No dosage adjustment necessary.

CrCl 11 to ≤31 mL/minute/1.73 m2: 1 tablet once daily.

CrCl ≤10 mL/minute/1.73 m2: There are no dosage adjustments provided in the manufacturer's labeling.

Hemodialysis (cetirizine <10% dialyzable): 1 tablet once daily.

Take after eating and with a full glass of water to decrease gastric upset.

Hypersensitivity: Cetirizine should not be used in individuals who have a known hypersensitivity or allergy to the medication or any of its components.

Pediatric use: Cetirizine is not recommended for use in children under the age of 3 years for the treatment of allergic rhinitis and under the age of 2 years for the treatment of allergic conjunctivitis.

Pregnancy and breastfeeding: The safety of Cetirizine use during pregnancy and breastfeeding has not been established, and its use should be avoided or used with caution in these situations.

Severe renal impairment: Cetirizine should be used with caution in individuals with severe renal impairment, as it may accumulate in the body and increase the risk of side effects.

It is important to talk to a healthcare professional before using Cetirizine to determine if it is safe and appropriate for individual use.

Concerns related to adverse effects:

• CNS depression: May cause drowsiness in some patients; instruct patient to use caution when driving or operating machinery. Effects may be additive with CNS depressants and/or ethanol.

• Nasal ulcerations: Periodically examine nasal mucosa for ulceration and consider discontinuing if ulceration occurs.

Cetirizine may cause liver problems, and using it with substantial quantities of ethanol may increase that risk.

Cetirizine is present in breast milk.

Concentrations of Cetirizine in breast milk increase with supplementation. When used as a dietary supplement, the recommended dietary allowance of Cetirizine is increased in breastfeeding patients compared to nonbreastfeeding patients. Doses of Cetirizine for the treatment of dyslipidemias are greater than those used as a dietary supplement. Due to the potential for serious adverse reactions in the breastfed infant (including hepatoxicity), the manufacturer recommends that breastfeeding be discontinued when Cetirizine is used for treatment of dyslipidemias.

There are no known food interactions with Cetirizine. However, it is recommended to avoid drinking alcohol while taking Cetirizine, as it can increase the risk of drowsiness and dizziness.

• Common Adverse effects:

Eye irritation or burning (when used as eye drops), Headache, Taste disturbances, Dry mouth, Fatigue or drowsiness, Dizziness, Nausea.

• Less Common Adverse effects:

Cardiovascular effects such as increased heart rate, palpitations, and high blood pressure.

Respiratory effects such as thickening of bronchial secretions, which can make it difficult to breathe, especially in patients with asthma or COPD.

Skin reactions such as rash, hives, and itching.

Allergic reactions such as anaphylaxis, which is a severe and potentially life-threatening allergic reaction.

Gastrointestinal effects such as abdominal pain and diarrhea.

Fatigue, weakness, and headache.

• Rare Adverse effects

Severe allergic reaction, such as swelling of the face, lips, tongue, or throat, difficulty breathing, or hives, Irregular heartbeat or palpitations, Confusion or hallucinations, Seizures, Yellowing of the skin or eyes (jaundice), Urinary retention or difficulty urinating, Muscle weakness or tremors ,Blood disorders such as thrombocytopenia or leukopenia, Elevated liver enzymes or liver damage,Stevens-Johnson syndrome or toxic epidermal necrolysis.

Cetirizine may interact with other drugs and may affect their effectiveness or increase the risk of side effects. Some of the common drug interactions of cetirizine include:

Central nervous system stimulants: Cetirizine may reduce the effectiveness of drugs that stimulate the central nervous system, such as caffeine or amphetamines.

Ketoconazole: Ketoconazole can increase the blood levels of cetirizine, which can increase the risk of side effects.

The common side effects of Cetirizine include the following :

Eye irritation or burning (when used as eye drops), Headache, Taste disturbances, Dry mouth, Fatigue or drowsiness, Dizziness and Nausea.

Symptoms: Confusion, diarrhea, dizziness, fatigue, headache, malaise, mydriasis, pruritus, restlessness, sedation, somnolence, stupor, tachycardia, tremor, and urinary retention.

Management: Symptomatic and supportive treatment. Gastric lavage may be performed following early ingestion.

Pharmacodynamic

Cetirizine, a piperazine derivative and metabolite of hydroxyzine, is an antihistamine which competitively and selectively inhibits H1 receptors in the gastrointestinal tract, blood vessels, and respiratory tract.

Pharmacokinetics

• Absorption: Rapidly absorbed from the gastrointestinal tract. Decreased rate of absorption with food. Time to peak plasma concentration: Approx 1 hour.

• Distribution: Enters breast milk. Volume of distribution: 0.56 L/kg. Plasma protein binding: 93%.

• Metabolism: Cetirizine is minimally metabolized in the liver, with less than 14% of the drug undergoing hepatic metabolism. The majority of the drug is eliminated unchanged in the urine. Cetirizine is primarily excreted in the urine, with approximately 70% of the drug being eliminated unchanged. The remainder of the drug is eliminated in the feces.

• Excretion: Mainly via urine (50% as unchanged drug); faeces (10%). Elimination half-life: 8 hours.

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1364710/
2. https://reference.medscape.com/drug/colestid-Cetirizine -342452
3. https://go.drugbank.com/drugs/DB00375
4. https://www.sciencedirect.com/topics/medicine-and-dentistry/Cetirizine
5. https://europepmc.org/article/med/6988203