Flustat

• Allergic Rhinitis:
  Relief of symptoms associated with seasonal and perennial allergic rhinitis, including sneezing, nasal congestion, runny nose, and itchy/watery eyes.
• Chronic Idiopathic Urticaria:
  Treatment of chronic hives and associated itching.
• Other Allergic Conditions:
  Relief of symptoms related to allergic conjunctivitis and other hypersensitivity reactions where antihistamines are indicated.
• Off-label Uses:
  May be used in dermatologic allergic conditions such as atopic dermatitis and insect bite reactions.

Adults and Children ≥ 6 years:

• 5 to 10 mg orally once daily.
• Maximum dose: 10 mg per day.

Children 2 to 5 years:

• 2.5 mg orally once daily; may increase to 5 mg per day in divided doses based on response.

Elderly:

• No specific dose adjustment required; start at lower doses if necessary due to increased sensitivity.

Renal Impairment:

• Mild to moderate impairment: no adjustment needed.
• Severe impairment (creatinine clearance < 10 mL/min): reduce dose to 5 mg once every other day.

Hepatic Impairment:

• No dose adjustment recommended.

Administration:

• Oral tablet, chewable tablet, or syrup.
• Can be taken with or without food.

Cetirizine hydrochloride is a selective antagonist of peripheral H1 histamine receptors. By competitively inhibiting H1 receptors, it prevents the binding of endogenous histamine released during allergic reactions. This inhibition reduces the classic allergic symptoms such as vasodilation, increased vascular permeability, and sensory nerve stimulation, leading to relief from itching, swelling, redness, and other allergy-related effects. Cetirizine is less sedating than first-generation antihistamines due to poor penetration of the blood-brain barrier.

• Absorption:
  Rapid and almost complete oral absorption with peak plasma concentrations within 1 hour.
• Bioavailability:
  Approximately 70%.
• Distribution:
  Volume of distribution ~0.3 L/kg. Limited central nervous system penetration.
• Protein Binding:
  93%–96%.
• Metabolism:
  Minimal hepatic metabolism; primarily excreted unchanged.
• Elimination:
  Mainly excreted via kidneys (70-85% unchanged).
  Elimination half-life approximately 7 to 10 hours.

• Pregnancy:
  FDA Pregnancy Category B — animal studies show no risk, but well-controlled human studies are lacking. Use only if clearly needed.
• Lactation:
  Excreted in small amounts into breast milk. Caution advised; monitor infants for sedation or irritability.

• Antihistamine
• Second-generation selective H1 receptor antagonist

• Known hypersensitivity to cetirizine, hydroxyzine, or any formulation excipients.

• Use caution in patients with renal impairment.
• May cause somnolence; avoid driving or operating heavy machinery until effects are known.
• Use with caution in patients with liver disease or the elderly.
• Avoid concomitant use with other CNS depressants to reduce additive sedation.

Common:

• Somnolence (drowsiness)
• Fatigue
• Dry mouth
• Headache
• Sore throat

Less Common:

• Dizziness
• Nausea
• Abdominal pain

Rare/Serious:

• Hypersensitivity reactions including rash, angioedema
• Rare cases of tachycardia or palpitations
• Very rarely, extrapyramidal symptoms

• CNS Depressants (e.g., alcohol, benzodiazepines):
  Increased sedation and CNS depression.
• Theophylline:
  May reduce clearance of cetirizine slightly; usually not clinically significant.
• No significant CYP450 enzyme involvement; low potential for drug-drug interactions.

• Updated guidelines recommend cetirizine as a preferred non-sedating antihistamine for allergic rhinitis and urticaria.
• Dosage adjustment recommendations clarified for severe renal impairment.
• Emphasis on patient counseling regarding possible sedation despite lower CNS penetration.

• Store at 20°C to 25°C (68°F to 77°F).
• Protect from moisture and light.
• Keep container tightly closed.
• Keep out of reach of children.