Ceterizine

# Ceterizine ## Overview - **Classification**: Second-generation antihistamine, H1-receptor antagonist - **Mechanism**: Selectively antagonizes peripheral H1-receptors, inhibiting histamine release and reducing allergic symptoms. ## Primary Indications 1. **Seasonal Allergic Rhinitis** - Symptomatic relief of sneezing, rhinorrhea, pruritus, lacrimation. 2. **Perennial Allergic Rhinitis** - Symptomatic relief of sneezing, rhinorrhea, pruritus, lacrimation. 3. **Chronic Idiopathic Urticaria** - Relief of pruritus and reduction in the number and size of hives. ## Adult Dosing ### Standard Dosing **Seasonal/Perennial Allergic Rhinitis, Chronic Urticaria** - **Dose**: **5 mg** or **10 mg** - **Frequency**: Once daily - **Route**: Oral (tablet, chewable, syrup) - **Maximum Dose**: **10 mg** per day ### Dose Adjustments - **Renal Impairment**: - CrCl 31-50 mL/min: **5 mg** once daily - CrCl 11-30 mL/min: **5 mg** every other day - CrCl < 10 mL/min (ESRD): **Contraindicated** - **Hepatic Impairment**: - Moderate/Severe: **5 mg** once daily - **Elderly Patients**: Start with **5 mg** once daily due to potential for decreased renal function. ## Pediatric Dosing ### Neonates (0-28 days) - **Dose**: Not recommended for this age group by manufacturers. - **Special Notes**: Use only under specialist supervision for specific conditions. No established dosing. ### Infants (1-12 months) - **Dose**: **2.5 mg** - **Frequency**: Once daily - **Maximum**: **2.5 mg** per day - **Special Notes**: Oral solution is preferred for accurate dosing. ### Children (1-5 years) - **Dose**: **2.5 mg** - **Frequency**: Once daily. May increase to **5 mg** once daily or **2.5 mg** every 12 hours. - **Maximum**: **5 mg** per day - **Special Notes**: Oral solution or chewable tablets available. ### Children (6-12 years) - **Dose**: **5 mg** or **10 mg** - **Frequency**: Once daily. May be given as **5 mg** every 12 hours. - **Maximum**: **10 mg** per day - **Special Notes**: Tablets, chewables, and solution are all appropriate. ### Adolescents (13-18 years) - **Dose**: **5 mg** or **10 mg** - **Frequency**: Once daily (same as adult dosing) - **Maximum**: **10 mg** per day ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to cetirizine, hydroxyzine, or excipients. - **Absolute**: End-stage renal disease (CrCl < 10 mL/min) requiring hemodialysis. ### Common Adverse Effects - **Common (1-10%)**: Drowsiness/sedation, fatigue, dry mouth, headache. - **Serious but Rare**: Hypersensitivity reactions (angioedema, anaphylaxis), seizures (rare). ### Key Drug Interactions - **CNS Depressants (e.g., alcohol, sedatives)**: Increased risk of CNS depression (drowsiness, impaired performance). - **Theophylline (400 mg/day)**: May decrease cetirizine clearance (minor clinical significance). - **Ritonavir**: May increase cetirizine exposure (monitor for increased adverse effects). ## Monitoring & Follow-up - **Before Treatment**: Assess renal and hepatic function, especially in elderly or patients with comorbidities. - **During Treatment**: Monitor for symptom improvement and adverse effects (e.g., drowsiness, dry mouth). - **Clinical Signs**: Watch for excessive sedation, dizziness, or paradoxical excitation in children. ## Clinical Pearls - 💡 **Timing**: Can be taken with or without food. Consider taking at night if sedation occurs. - 💡 **Less Sedating**: Generally less sedating than first-generation antihistamines like diphenhydramine. - 💡 **Formulations**: Available as oral tablets, chewable tablets, and oral solution for pediatric and ease-of-swallowing needs. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.