Astemizole, a new long-acting antihistamine, (H1 receptor antagonist), 10 mg taken once daily was found to be an effective prophylactic treatment for the symptoms of allergic rhinitis in 75% (twelve from sixteen) of subjects in a double-blind placebo-controlled study.
Cetirizine is the most potent antihistamine available and has been subjected to more clinical study than any other.
Long term use of some antihistamines may increase your risk of dementia. Diphenhydramine (Benadryl®) blocks the effects of a neurotransmitter called acetylcholine. This neurotransmitter is vital for memory and learning.
Desloratadine is a long-acting tricyclic histamine antagonist selective for H1 receptors. It is a major metabolite of loratadine, which, after ingestion, is metabolized extensively to active metabolite 3-hydroxydesloratadine.
Allergists recommend long-acting, non-sedating antihistamines — ones that won't make you sleepy — for everyday use. Though you may know them by their brand names, the generic versions tackle the same problems: Cetirizine (Zyrtec®, Aller-Tec®, Wall-Zyr®). Fexofenadine (Allegra®, Aller-ease®, Aller-Fex®, Wal-Fex®).
Adults—1 to 2 milligrams (mg) every eight to twelve hours as needed. Children 12 years of age and older—0.5 mg to 1 mg two times a day as needed. Children 4 to 12 years of age—Use and dose must be determined by your doctor. Children and infants up to 4 years of age—Use is not recommended .
Regular use for chronic allergies
You may take an antihistamine every day to keep long-term allergy symptoms under control.
David Shih, executive vice-president of strategy and former chief medical officer at CityMD, explained to The Cut that second-generation antihistamines, like the commonly available over-the-counter drug loratadine, are generally safe for long-term use.
In conclusion, cetirizine produced greater relief of seasonal allergic rhinitis symptoms than fexofenadine at 12 hours postdose and over the 5- to 12-hour postdose period.
“Zyrtec is found to be more potent, or stronger, in laboratory studies, compared with Claritin,” says Dr. Kung. “It also reaches a higher concentration in the skin, which can be more helpful for skin-related allergies. However, Zyrtec has a greater chance of making you sleepy while taking it.”
Bilastine is a new second generation non-sedating antihistamine (NSAH). Bilastine belongs to the same pharmacological class as other Schedule 2 substances such as fexofenadine, loratadine and cetirizine, which are also used for the symptomatic treatment of allergic rhinitis and urticaria.
What Is Zyrtec? Zyrtec is an FDA-approved, over-the-counter, long-acting antihistamine (up to 24 hours) that doesn't require a prescription.
The best antihistamine to take during the day to help with allergic skin rashes is Curist Allergy Relief (levocetirizine) or another antihistamine like fexofenadine or loratadine, which can provide 24-hour symptom relief without making you feel sleepy.
Cetirizine is unlikely to do you any harm if you take it for a long time. However it's best to take cetirizine only for as long as you need to. If you take it regularly over a long period there's a very small chance of severe itching if you stop treatment suddenly.
Is it safe to take Zyrtec every day? Yep. "When taken in the recommended doses, antihistamines can be taken daily. This is especially true with Zyrtec, since it doesn't show decreasing effectiveness if used daily," says Sima Patel, MD, an allergist at New York Allergy & Sinus Centers.
Non-sedating antihistamines are used in the long-term control of allergy, as in hay fever, eczema, sinusitis, and chronic urticaria. No serious side effects have been reported. Tolerance is not a problem.
These common side effects include sedation, impaired motor function, dizziness, dry mouth and throat, blurred vision, urinary retention and constipation. Antihistamines can worsen urinary retention and narrow angle glaucoma. The antihistamines rarely cause liver injury.
To sum it up, all first-generation H1 antihistamines should be taken close to bedtime or when you're able to sleep. Second-generation H1 antihistamines and H2 blockers can typically be taken at any time of the day. One exception to this is cetirizine, which can cause drowsiness for up to 14% of those who take it.
Is it okay to take ZYRTEC® over a long period of time? The ZYRTEC® package label doesn't state a limit on how long you can take ZYRTEC®. Talk to your doctor if you have any questions, especially if you're taking other medicines or being treated for any other conditions.
The usual dose for treating hives is 180mg once a day for adults and children aged 12 years and over.
The recommended dose is one tablet (180 mg) daily. Take your tablet with water before a meal. This medicine starts to relieve your symptoms within 1 hour and lasts for 24 hours. If you take too many tablets, contact your doctor or the nearest hospital emergency department immediately.