Zyrtec (Cetirizine) Dosing for Itchiness
For adults and children 6 years and older, the standard dose of cetirizine is 10 mg once daily, which can be increased up to 20-40 mg daily if symptoms are inadequately controlled, though doses above 10 mg are off-label. 1
Standard Dosing
- Adults and children ≥6 years: 10 mg once daily (do not exceed one 10 mg tablet in 24 hours at standard dosing) 1
- Peak plasma levels are reached within 1 hour after intake, providing relatively rapid symptom relief 2
- A 5 mg dose may be appropriate for less severe symptoms 1
- Adults ≥65 years: Consult a physician before use, as lower doses may be needed 1
- Liver or kidney disease: Consult a physician for dose adjustment 1
Dose Escalation for Refractory Itching
When standard 10 mg daily dosing fails to control symptoms adequately, increasing cetirizine to 20 mg once daily is effective and well-tolerated. 3
Evidence for Higher Doses:
- Doubling to 20 mg daily significantly improves wheal severity, itching, and quality of life in patients who don't respond to 10 mg 3
- Doses up to 40 mg daily have been used safely in dermatologic conditions, particularly urticaria and atopic dermatitis, with dose-dependent but generally mild adverse effects 2
- In difficult-to-treat urticaria, approximately 75% of patients respond to higher-than-conventional antihistamine doses (up to 4-fold increase), while only 15% respond adequately to standard doses 4
Important Caveat:
- One study found only 5% of patients with severe chronic urticaria responded to tripled doses (30 mg daily), suggesting that most patients with truly refractory disease will require alternative therapies beyond dose escalation 5
- Individual dosage should be based on symptom severity rather than a one-size-fits-all approach 2
Timing and Duration
- Once daily dosing is standard; timing can be adjusted to ensure highest drug levels when symptoms are most problematic 6
- Cetirizine may cause dose-dependent somnolence, particularly at higher doses, though at 10 mg it does not impair driving performance 2
- For chronic conditions, benefits last only during active treatment; symptoms typically return after discontinuation 7
Special Populations
- Elderly patients: Should avoid sedating antihistamines long-term due to dementia risk; cetirizine at standard doses is acceptable but use caution with higher doses due to increased sedation 6
- Renal impairment: Dose reduction required, as cetirizine is eliminated largely unchanged by renal excretion 2
- Uraemic pruritus: Cetirizine is specifically not effective and should not be used 6
Safety Profile
- No cardiac toxicity or significant drug interactions 2
- No teratogenicity evidence, though pregnancy category should be considered 2
- Adverse effects are primarily somnolence, which is dose-dependent and generally mild 2
- Increasing doses up to 4-fold does not increase somnolence significantly in most patients 4