What is the recommended dosage of Zyrtec (Cetirizine) for treating hives?

Zyrtec (Cetirizine) 10mg for Hives

For adults and children 6 years and older with hives (urticaria), take one 10mg tablet of Zyrtec once daily, with the option to increase up to 20mg daily if symptoms are not adequately controlled at the standard dose. 1

Standard Dosing

• Adults and children ≥6 years: 10mg once daily 1
• Do not exceed one 10mg tablet in 24 hours at the standard dose 1
• A 5mg dose may be appropriate for less severe symptoms 1

Dose Escalation for Inadequate Response

If hives are not adequately controlled with the standard 10mg daily dose, evidence supports increasing the dose:

• Cetirizine can be increased to 20mg once daily for patients with difficult-to-treat urticaria who don't respond to standard dosing 2, 3
• This doubled dose has been shown to significantly improve wheal severity, itching, and quality of life without compromising safety 2
• European guidelines support increasing antihistamine doses up to 4-fold (40mg daily) in refractory cases, though evidence is strongest for doubling to 20mg 4, 3

Efficacy Evidence

Cetirizine 10mg once daily demonstrates superior efficacy compared to placebo:

• Achieves complete suppression of urticaria in significantly more patients (RR 2.72,95% CI 1.51 to 4.91) in both short-term (≤2 weeks) and intermediate-term (2 weeks to 3 months) treatment 3
• Shows rapid onset of action, with reduction in urticarial episodes and pruritus evident after just 1 day of treatment 5
• Equivalent efficacy to hydroxyzine 25mg three times daily but with better tolerability 5

Special Populations

Renal impairment: The dose should be halved (5mg daily) in patients with moderate to severe renal impairment 6

Hepatic impairment: Consult a physician before use 1

Adults ≥65 years: Consult a physician before use 1

Children <6 years: Consult a physician for appropriate dosing 1

Pregnancy: Cetirizine is classified as FDA Pregnancy Category B, with no evidence of fetal harm, though well-controlled human studies are lacking; use only if clearly needed 6

Common Pitfalls to Avoid

• Don't abandon cetirizine prematurely: Approximately 75% of patients with difficult-to-treat urticaria respond to higher-than-conventional doses (up to 20mg daily) 4
• Individual response varies greatly: About 15% are excellent responders to standard doses, 10% are non-responders, and 75% benefit from dose escalation 4
• Sedation is minimal: Unlike older antihistamines (hydroxyzine), cetirizine at standard and doubled doses does not significantly increase somnolence 4, 5

When Standard Treatment Fails

If symptoms persist despite cetirizine 20mg daily, consider:

• Switching to or adding levocetirizine (the active enantiomer of cetirizine) at 5-20mg daily 4, 3
• Adding an H2-antihistamine for additional benefit 6
• Referral for alternative therapies such as omalizumab or immunosuppressants 7