RHIZIN 10 MG TABLET

Indications

• Allergic rhinitis (hay fever)
• Chronic urticaria (hives)
• Allergic conjunctivitis

Dosage

Children: Refer to BNF for Children for specific dosing recommendations.

Adults: Refer to BNF for specific dosing recommendations.

Mechanism of action

Cetrizine exerts its pharmacological effect primarily by selectively antagonizing peripheral H1 receptors. This prevents histamine from binding to its receptors, thereby reducing the symptoms of allergic reactions such as inflammation, itchiness, and mucus secretion. Additionally, it has some affinity for the central nervous system but is less sedating than first-generation antihistamines due to its limited ability to cross the blood-brain barrier.

Pharmacodynamics

Cetrizine displays a rapid onset of action, typically within one hour of administration, with a duration of effect lasting up to 24 hours. It is effective in reducing the signs and symptoms of allergic rhinitis, such as sneezing and nasal itching, as well as urticaria, by blocking the actions of endogenous histamine. The drug has a favorable safety profile with fewer sedative effects compared to first-generation antihistamines.

Pharmacokinetics

Cetrizine is well-absorbed from the gastrointestinal tract, with peak plasma concentrations occurring approximately one hour after oral administration. It undergoes minimal hepatic metabolism and is primarily excreted unchanged in the urine. Its half-life is about 8 to 10 hours, allowing for once-daily dosing in most cases. Renal impairment may necessitate dosage adjustments due to decreased clearance.

Contra-indications

• Hypersensitivity to cetirizine or any of its components
• Severe renal impairment

Adverse effects

• Drowsiness
• Dry mouth
• Dizziness
• Fatigue
• Nausea
• Headache

Interactions

• Alcohol may enhance the sedative effects
• Caution when used with other CNS depressants
• Potential interaction with theophylline which may reduce cetirizine clearance

Precautions

• Use with caution in patients with epilepsy or at risk of seizures
• May impair the ability to perform tasks requiring mental alertness
• Caution in patients with liver impairment

Pregnancy

Cetirizine should be used in pregnancy only if the benefits justify the risks to the fetus. Limited data available on safety.

Breast-feeding

Cetirizine is excreted in breast milk; caution is advised when administering to nursing mothers.

Storage

Store in a cool, dry place, away from direct sunlight. Keep out of reach of children.

Formulations

• Tablets
• Oral solution
• Chewable tablets