How much antihistamine can i take in 24 hours
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Recommended Antihistamine Dosages in a 24-Hour Period
Cetirizine Dosage and Efficacy
Cetirizine is commonly administered at a dosage of 10 mg once daily. Studies have shown that this dosage is effective in suppressing histamine-induced wheals and flares for up to 24 hours1 3. Cetirizine has demonstrated a consistent antihistaminic effect, with a significant reduction in skin reactions throughout the day3. It is well-tolerated and does not typically cause serious adverse events3.
Fexofenadine Dosage and Efficacy
Fexofenadine is available in dosages of 120 mg and 180 mg, both of which are taken once daily. Research indicates that both dosages are effective in reducing symptoms of allergic rhinitis and skin reactions for a full 24-hour period2 3 5. However, the 180 mg dose may offer slightly better suppression of histamine-induced wheals and flares compared to the 120 mg dose3. Fexofenadine is also noted for its minimal sedative effects, making it a suitable option for daytime use5.
Loratadine Dosage and Efficacy
Loratadine is typically prescribed at a dosage of 10 mg once daily. This dosage has been shown to effectively reduce histamine-induced skin reactions and symptoms of allergic rhinitis for up to 24 hours1 2 4. Loratadine is also well-tolerated and has a low incidence of drowsiness compared to other antihistamines2.
Chlorpheniramine Dosage and Efficacy
Chlorpheniramine is usually taken at a dosage of 4 mg every 4 to 6 hours, not exceeding 24 mg in a 24-hour period. While effective, it is less potent compared to newer antihistamines like cetirizine and fexofenadine1 2. Additionally, chlorpheniramine is more likely to cause drowsiness, which can limit its use during the day2.
Ebastine Dosage and Efficacy
Ebastine is administered at a dosage of 20 mg once daily. Studies have shown that this dosage is effective in reducing histamine-induced skin reactions and is superior to cetirizine and loratadine in some cases4. Ebastine is well-tolerated and does not cause significant drowsiness, making it a viable option for daily use4.
Olopatadine and Levocetirizine Dosage and Efficacy
Olopatadine is taken at a dosage of 5 mg twice daily, while levocetirizine is taken at 5 mg once daily. Both antihistamines are effective in suppressing histamine-induced wheals and flares for up to 24 hours6. Olopatadine has shown a more potent effect compared to levocetirizine, particularly in severe cases of urticaria6. Both medications are well-tolerated with minimal sedative effects6.
Conclusion
The recommended dosages for common antihistamines in a 24-hour period are as follows:
- Cetirizine: 10 mg once daily
- Fexofenadine: 120 mg or 180 mg once daily
- Loratadine: 10 mg once daily
- Chlorpheniramine: 4 mg every 4-6 hours (maximum 24 mg/day)
- Ebastine: 20 mg once daily
- Olopatadine: 5 mg twice daily
- Levocetirizine: 5 mg once daily
These dosages are effective in managing allergic reactions and are generally well-tolerated with minimal side effects. Always consult with a healthcare provider before starting any new medication regimen.
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Most relevant research papers on this topic
A double-blind, single-dose, crossover comparison of cetirizine, terfenadine, loratadine, astemizole, and chlorpheniramine versus placebo: suppressive effects on histamine-induced wheals and flares during 24 hours in normal subjects.
Cetirizine and terfenadine are the most effective H1-receptor antagonists for suppressing histamine-induced wheals and flares, followed by loratadine, astemizole, and chlorpheniramine.
RCT
Highly CitedClinical pharmacology of H1-antihistamines in the skin.
Fexofenadine and loratadine effectively suppress skin wheals and flares, while chlorpheniramine's use for allergic skin disorders needs reexamination.
RCTTwenty-four hours of activity of cetirizine and fexofenadine in the skin.
Cetirizine has a longer duration of action and better consistency in inhibiting histamine-induced skin reactions compared to fexofenadine (120 and 180 mg).
RCTEfficacy of ebastine, cetirizine, and loratadine in histamine cutaneous challenges.
Ebastine (20 mg/day) is an effective once-daily antihistamine with superior efficacy compared to cetirizine (10 mg) and loratadine (10 mg) on overall skin wheal response after single and multiple doses.
RCTDouble-blind, placebo-controlled study comparing the efficacy and safety of fexofenadine hydrochloride (120 and 180 mg once daily) and cetirizine in seasonal allergic rhinitis.
Once-daily fexofenadine is a valuable addition to the nonsedating H1 receptor antagonists for treating seasonal allergic rhinitis, with both doses being effective and safe.
RCT
Large Human TrialHighly CitedEvaluation of the antihistamine effects of olopatadine and levocetirizine during a 24‐h period: A double‐blind, randomized, cross‐over, placebo‐controlled comparison in skin responses induced by histamine iontophoresis
Olopatadine is more potent than levocetirizine in controlling mild to moderate urticaria, while levocetirizine may need an additional dose to control severe urticaria.
RCTBioavailability of Triprolidine as a Single Agent or in Combination With Pseudoephedrine: A Randomized, Open‐Label Crossover Study in Healthy Volunteers
Triprolidine's bioavailability as a single agent and combined with pseudoephedrine is comparable, with higher maximum plasma concentrations in the combination tablet.
RCT
Very Rigorous JournalAllergen-induced increase in nonspecific nasal reactivity is blocked by antihistamines without a clear-cut relationship to eosinophil influx.
Antihistamines terfenadine and cetirizine effectively reduce nasal symptoms and inhibit allergen-induced nonspecific nasal reactivity, suggesting they possess other properties besides H1-receptor antagonists.
RCTThe development of subsensitivity to chlorpheniramine.
Subsensitivity to antihistamines develops between 7 and 21 days of therapy and cannot be completely overcome by doubling the dose, possibly due to increased H1 receptor number.
RCTA double-blind, randomized, single-dose, crossover comparison of levocetirizine with ebastine, fexofenadine, loratadine, mizolastine, and placebo: suppression of histamine-induced wheal-and-flare response during 24 hours in healthy male subjects.
Levocetirizine is the most potent and consistently effective H1 antihistamine for blocking the cutaneous response to histamine, potentially improving treatment of allergic disorders.
RCTHighly Cited