Cetirizine

Cetirizine is a second-generation antihistamine medication used to treat allergic rhinitis. Cetirizine was initially approved by the FDA as a prescription-only medicine in 1995 before becoming available over the counter in 2007. It is good at relieving sneezing, rhinorrhea, and watery eyes. It does not cross the blood-brain barrier to the same amount as the first generation. It also successfully alleviates hives and itching in patients with idiopathic urticaria. Cetrizine is a safe and efficient therapy for urticaria.

BRAND NAMES:

Aller- tec  -  It consists of cetirizine hydrochloride as an active ingredient available as Aller–tec Cetirizine hydrochloride 10mg or 5mg antihistamine tablets.

Aller – tec D– Cetirizine hydrochloride 5mg and pseudoephedrine hydrochloride 120mg are combinational active ingredients in Aller – tec D.

Quzyttir – Quzyttir is a cetirizine hydrochloride injection supplied in 2ml amber color glass vials for single use. This vial contains 1ml drug solution and 10mg of cetirizine hydrochloride.

Zyrtec – Zyrtec is mainly used in children and consists of cetirizine hydrochloride as the main active ingredient with strengths of 5mg and 10mg. These are available as tablets, syrup, and chewable tablets.

Zyrtec D - These are available in the form of tablets with combinational active ingredients of cetirizine hydrochloride and pseudoephedrine.

MECHANISM OF ACTION:  

It is a highly selective and fast-acting histamine H receptor antagonist. It acts by blocking the histamine receptor and suppressing inflammatory reactions caused by histamine. Cetrizine does not cross the blood-brain barrier to a large extent, avoiding the neurons of the central nervous system. As a result, it produces less sedation levels. Cetrizine effectively reverses many of the effects of histamine. It can handle anti-inflammatory activity by reducing the infiltration of inflammatory cells in allergic rhinitis. It decreases vascular permeability, decreasing fluid escaping to tissues from capillaries.

PHARMACOKINETICS:

Absorption: It takes 1 hour to reach its highest plasma concentration. Cetrizine is absorbed in the gastrointestinal system and is primarily excreted by the kidney. Cetirizine starts acting after 20 to 60 minutes and lasts for at least 24 hours. Cetirizine pills and syrups have equal bioavailability.

Distribution: The mean plasma protein binding is 93%.

Metabolism: It is metabolized by oxidative O-dealkylation to a metabolite with insignificant antihistaminic activity.

Excretion: 70 – 85% of administered drug is eliminated through urine and remaining through feces.

PHARMACODYNAMICS:

As cetirizine has anti-inflammatory properties it helps in asthma management. The active metabolite of piperazine H1 receptor antagonist eliminates the symptoms of chronic idiopathic urticarial and seasonal allergic rhinitis. H1 receptor occupancy by cetirizine is dose-dependent, while cetirizine of 5mg and 10mg are non sedating or mildly sedating doses. The higher dose of 20 mg was found to be drowsy.

DOSAGE AND ADMINISTRATION:

Cetirizine is available in the form of orally disintegrating tablets, syrups, solutions, and capsules. The dose will be administered depending on the severity of the patient's condition and age.

• 5 to 10mg /d daily dosage is recommended for children between 6 to 11 years or older.
• Children between 6 to 2 months are recommended to take 2.5mg syrup once daily.
• 0.24% cetirizine hydrochloride eye drops in 5ml and 7.5ml bottles.
• Cetrizine 5mg combined with pseudoephedrine Hcl 2mg is a nasal decongestant that relieves sinus congestion.
• IV administration of cetirizine 10mg to treat acute urticarial in adults aged 12 and older.

CONTRAINDICATIONS:

Cetrizine is contraindicated in patients with known hypersensitivity to its ingredients and hydroxyzine.

DRUG INTERACTIONS:

Patients should discuss with their doctor before using cetirizine about the drugs that they already have been using for other treatments.

• Using cetirizine with drugs that depress your central nervous system can increase sleepiness. It can affect your nervous system functionalities.
• Cetrizine decreases gabapentin plasma concentrations and reduces systematic exposure to gabapentin.
• It should not administered with erdafitinib an inhibitor of P-glycoprotein.
• It has some serious interactions with the drugs Isocarboxazid and tranylcypromine.
• It has drug interactions with painkillers(antipyrine), anti -HIV drugs(ritonavir),anti-fungal(ketoconazole), antibiotics(azithromycin, erythromycin), respiratory medicines(theophylline).

FOOD INTERACTIONS:

Avoid alcohol. It can be taken with or without food.

ADVERSE EFFECTS:

• Dizziness
• Sore throat
• Sneezing or blocked nose
• Headache
• Dry mouth
• Anaphylaxis
• Fatigue
• Ocular hyperemia

TOXICITY:

Symptoms appear as 

• Liver damage
• Drowsiness
• Irritability
• Hyperthermia
• Agitation

STORAGE:

Medicine should be stored at room temperature in a closed container. Stay away from direct sunshine and moisture. Keep from freezing.