Description

Reactine (Anti-Allergy Medication)

Description

Reactine is an over-the-counter second-generation antihistamine containing Cetirizine Hydrochloride, widely used to relieve symptoms of allergic rhinitis, urticaria (hives), and other histamine-mediated conditions. It is valued for its rapid onset, 24-hour duration, and improved tolerability relative to first-generation antihistamines.

Active Ingredient

Cetirizine Hydrochloride is a selective H₁ receptor antagonist, minimizing allergic symptoms such as sneezing, rhinorrhea, nasal and ocular itching, and skin urticaria. It is the active component in Reactine formulations, including tablets, chewables, and syrup.

Pharmacological Action

Cetirizine selectively inhibits peripheral histamine H₁ receptors, blocking histamine-mediated inflammatory responses. It exhibits minimal central nervous system penetration, reducing sedation risk. Cetirizine also demonstrates modest anti-inflammatory activity via inhibition of NF‑κB and modulation of eosinophil chemotaxis and cytokine release. Its high tissue binding to albumin (~93 %) and slow metabolism contribute to its prolonged effect.

Indications

Reactine (Cetirizine Hydrochloride) is indicated for:

• Seasonal allergic rhinitis (hay fever)
• Perennial allergic rhinitis
• Chronic idiopathic urticaria (hives)
• Allergic conjunctivitis (adjunct relief for itching and redness)
• Other histamine-mediated dermatoses or mild allergic conditions

Dosage and Administration

• Adults and children ≥6 years: 10 mg once daily.
• Children 2–5 years: Pediatric syrup 2.5–5 mg once daily, depending on weight.
• Pediatric chewables: Follow label dosing; usually 5 mg twice daily in children under 12.
• Renal impairment: Dose reduction to 5 mg daily for CrCl 11–31 ml/min or in elderly, per regulatory guidance.

Take with or without food. Usually dose strength is 10 mg tablet or equivalent in syrup.

Side Effects

• Drowsiness and fatigue (sedation rates ~10–15 %).
• Dry mouth common.
• Occasional headache, dizziness, or abdominal discomfort.
• Rare: urinary retention or palpitations.
• Very rare: pruritus after discontinuation (FDA warning May 16, 2025).

Contraindications

• Hypersensitivity to Cetirizine, hydroxyzine, or formulation components.
• Severe renal impairment without dose adjustment.
• Use during lactation generally not recommended; pregnancy category B (use if necessary).

Precautions

• Caution when driving or operating machinery due to possible sedation.
• Use in elderly or pediatric populations with reduced dosing and monitoring.
• Discontinuation after prolonged use may provoke severe itching (pruritus) — follow tapering recommendations.

Interactions

Cetirizine is not metabolized by CYP450 enzymes, meaning low risk of interactions with common medications that affect liver enzymes. However, caution is advised with:

• CNS depressants—may increase sedation.
• Anticholinergic medications—may exacerbate dry mouth or urinary retention.
• Lab interference—may affect immunoassay results or inflammatory biomarkers.

Overdose

Excessive ingestion may result in extreme drowsiness, tachycardia, or headache. Supportive care, monitoring of vital signs, and hydration are standard interventions. In children, monitor for excitation or sedation.

Storage

• Store at room temperature, away from moisture and heat.
• Do not freeze.
• Keep out of reach of children and pets.

Mechanism of Action

Cetirizine binds selectively to peripheral H₁ receptors, preventing histamine from producing allergy symptoms. It does not significantly penetrate the CNS, thus causing less sedation compared to first-generation antihistamines. The drug also exhibits modest inhibition of inflammatory mediators and mast cell stabilization.

Clinical Studies and Evidence

A large randomized controlled trial showed that Cetirizine 10 mg daily significantly reduces symptoms of seasonal allergic rhinitis and chronic urticaria compared to placebo and is well tolerated (Grant et al., 1995). Another network meta-analysis in 2023 confirmed cetirizine’s efficacy among H₁ antihistamines, with substantial symptom relief albeit slightly higher sedation risk than fexofenadine (Hong et al., 2023)

Use in Special Populations and Sports

Reactine is approved for children as young as 6 months (in syrup form), with demonstrated safety in pediatric allergic rhinitis. Use in elderly should consider renal clearance—dose adjustment required for CrCl <30 ml/min. For athletes, cetirizine is generally permitted by WADA but may cause sedation affecting performance or reaction time; caution advised before competitions.

Comparison with Other Antihistamines

Compared to loratadine and fexofenadine, cetirizine is similarly effective but may cause mild drowsiness more rapidly. It shows faster onset than fexofenadine and stronger urticaria suppression in clinical trials. Levocetirizine (L-isomer) may offer reduced sedation at lower doses.

Summary

Reactine (Cetirizine Hydrochloride) is a reliable, effective, and generally safe antihistamine medication for allergic rhinitis, hives, and related conditions. With once-daily dosing and a favorable safety profile, it is widely used in adults and children. Use should be tailored in renal impairment, and discontinuation should be managed to minimize withdrawal pruritus risk.

References

• Grant et al., 1995 – Cetirizine efficacy in allergic rhinitis
• Hong et al., 2023 – Comparative meta‑analysis of H1 antihistamines