Onset of action of cetirizine

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Cetirizine Onset of Action: Timing and Comparative Effectiveness

Onset of Action in Adults: Seasonal Allergic Rhinitis and Histamine Challenge

Multiple studies show that cetirizine has a rapid onset of action for relieving symptoms of allergic rhinitis. In controlled environmental exposure studies, cetirizine begins to reduce symptoms as early as 1 hour after a single oral dose, which is faster than loratadine, whose onset is typically around 1.5 to 3 hours or longer 12410. In direct comparisons, cetirizine consistently provides earlier and more significant symptom relief than loratadine during the first hours after administration 1410.

Onset of Action: Measured by Histamine-Induced Wheal and Flare

When measuring the suppression of histamine-induced skin reactions, cetirizine shows significant activity within 1 to 2 hours. Studies in both adults and children demonstrate that cetirizine can suppress wheal and flare responses as early as 15 to 30 minutes after dosing, with near-maximal effects seen from 1 to 2 hours onward 358. Cetirizine’s onset is similar to fexofenadine in these models, with both achieving strong effects within about 2.5 hours .

Onset of Action in Children

In pediatric populations, cetirizine also demonstrates a rapid onset. Suppression of histamine-induced wheal and flare is significant from 15 minutes after dosing, with strong effects maintained for up to 24 hours. Cetirizine acts more quickly and with greater potency than loratadine in children, especially within the first hour after administration 58.

Nasal and Topical Cetirizine: Rapid Local Effects

Topical (nasal) cetirizine formulations can act even faster. In studies using nasal histamine challenge, topical cetirizine significantly reduced plasma exudation and nasal symptoms within 5 to 15 minutes of application, indicating a very rapid local onset . For oral cetirizine, nasal symptom relief is evident within 1.5 hours, and cetirizine is more effective than loratadine at this early time point .

Combination Formulations

Cetirizine combined with pseudoephedrine (a decongestant) has an onset of action reported at approximately 30 minutes, providing rapid relief of nasal symptoms in allergic rhinitis .

Summary of Onset Ranges

Across studies, the onset of action for oral cetirizine is generally between 30 minutes and 2 hours, with most patients experiencing significant symptom relief within 1 hour. This rapid onset is consistent in both adults and children and is faster than loratadine in direct comparisons 1245810. Topical cetirizine acts even more quickly, within minutes .

Conclusion

Cetirizine is a second-generation antihistamine with a rapid onset of action, typically providing noticeable symptom relief within 1 hour of oral administration and even faster when used topically. It acts more quickly than loratadine and is comparable to fexofenadine in onset. This makes cetirizine a strong choice for patients seeking fast relief from allergic symptoms.

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Most relevant research papers on this topic

Comparative onset of action and symptom relief with cetirizine, loratadine, or placebo in an environmental exposure unit in subjects with seasonal allergic rhinitis: confirmation of a test system.

Cetirizine acts earlier and is more effective than loratadine or placebo in reducing symptoms of seasonal allergic rhinitis in subjects undergoing a controlled pollen challenge.

RCTLarge Human Trial

2001·

57citations

·J. Day et al.

Onset of action for the relief of allergic rhinitis symptoms with second-generation antihistamines.

Cetirizine has a shorter onset of action for relief of allergic rhinitis symptoms than loratadine, while fexofenadine has an onset of action within 60 minutes.

Systematic Review

2004·

16citations

·W. Greisner

Similar rapid onset of action and magnitude of effect of fexofenadine and cetirizine as assessed by inhibition of histamine-induced wheal-and-flare reaction.

Fexofenadine and cetirizine have comparable onset of action times and similar frequencies of inhibition, as assessed by the occurrence of 95% inhibition of histamine-induced wheal and flare.

RCT

2004·

12citations

·A. Purohit et al.

Onset of action in the nasal antihistaminic effect of cetirizine and loratadine in patients with allergic rhinitis

Cetirizine has a more rapid onset of action in the nose than loratadine for treating allergic rhinitis, with similar efficacy at therapeutic dosages after 4 hours.

RCT

1997·

21citations

·N. Frossard et al.

H1‐antihistaminic activity of cetirizine and fexofenadine in allergic children

Cetirizine 10mg has a faster onset of H1-antihistaminic activity, a 24-hour duration of action, and greater H1-activity than fexofenadine 30mg in children aged 6-11 years.

RCT

2003·

25citations

·F. Simons et al.

Controlled Comparison of the Efficacy and Safety of Cetirizine 10 mg o.d. and Fexofenadine 120 mg o.d. in Reducing Symptoms of Seasonal Allergic Rhinitis

Cetirizine and fexofenadine effectively reduce seasonal allergic rhinitis symptoms, with cetirizine showing a longer duration of action and better symptom relief for sneezing.

RCT

2001·

65citations

·F. Horak et al.

Onset of action of a topical antihistamine as assessed by histamine challenge-induced plasma exudation responses.

Topical cetirizine-dinitrate has an early onset of action, inhibiting histamine challenge-induced mucosal exudation of plasma within 5 to 10 minutes.

RCT

2006·

4citations

·M. Korsgren et al.

Clinical pharmacology of the H1‐receptor antagonists cetirizine and loratadine in children

Cetirizine and loratadine both have excellent antihistaminic activity in children, with rapid onset of action and a 24-hour duration of action in this population.

RCT

2000·

28citations

·F. Simons et al.

Cetirizine/pseudoephedrine.

Cetirizine 5mg and pseudoephedrine SR 120m twice daily for 2 to 3 weeks effectively reduces symptoms of seasonal or perennial allergic rhinitis, with common adverse events being dry mouth, insomnia, headache, somnolence, asthenia, and nervousness.

RCT

2001·

0citations

·K. Wellington et al.

Onset of action and efficacy of terfenadine, astemizole, cetirizine, and loratadine for the relief of symptoms of allergic rhinitis.

Cetirizine and terfenadine provide faster onset of action and efficacy for allergic rhinitis relief, while loratadine and astemizole show lower rankings.

RCTHighly Cited

1997·

78citations

·J. Day et al.

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