Cetirizine Dosage for Adult Allergies
For an adult with normal renal function and no significant medical history, the standard cetirizine dose is 10 mg once daily. 1
Standard Adult Dosing
- The FDA-approved dose is 10 mg once daily, with explicit instruction not to exceed one 10 mg tablet in 24 hours. 1
- A 5 mg dose may be appropriate for less severe symptoms, though clinical evidence shows 10 mg provides superior symptom control. 1, 2
- Cetirizine is taken once daily due to its 8.3-hour elimination half-life and 24-hour duration of action. 3, 4
Timing Considerations
- Cetirizine has the shortest time to maximum concentration among second-generation antihistamines, reaching peak levels within 1 hour, making it advantageous when rapid symptom relief is needed. 3, 5
- If mild sedation occurs (13.7% of patients vs 6.3% with placebo), consider evening or bedtime dosing to allow sedative effects to occur during sleep. 6, 7
- Adjust timing to ensure highest drug levels coincide with anticipated symptom periods. 3
Dose Escalation for Refractory Cases
- For patients who don't respond adequately to 10 mg daily, increasing the dose above the manufacturer's licensed recommendation (up to 40 mg daily) has become common practice when benefits outweigh risks, though this is off-label. 3, 7
- This dose escalation is supported by British Association of Dermatologists guidelines (Quality of evidence III, Strength of recommendation C). 7
Important Caveats
- Cetirizine may cause mild drowsiness, particularly at higher doses, distinguishing it from completely non-sedating alternatives like fexofenadine. 3, 6
- Patients should be counseled about potential sedation and advised against combining with other CNS depressants. 6, 7
- No dose adjustment is needed for hepatic impairment in patients with normal renal function. 3
- Cetirizine has no clinically significant drug interactions and no cardiac toxicity. 4, 5