Antihistamines, like loratadine (Claritin), fexofenadine (Allegra), and cetirizine (Zyrtec), are another popular choice for treating allergies. And studies show that people do not build up resistance to these medications.
Myth #11: You can build up a tolerance to antihistamines through continuous use. “There is no scientific evidence that you can develop a tolerance to oral antihistamine pills, such as Allegra, Zyrtec and Claritin,” Wierzbicki clears up.
So if, for example, cetirizine doesn't seem to help, try fexofenadine or loratadine, Hong says.
Sometimes, people experience less and less relief from their antihistamines over time. When this happens, the culprit may be an antihistamine tolerance (read above), or a worsening or evolution of allergies and symptoms. Over time, allergies may become more severe or cause cross-reactivity with similar substances.
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.
Yes, most people can take antihistamines every day, if they have daily symptoms of their allergies.
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.
Why do antihistamines stop working? Antihistamines can stop working because your allergies might be getting worse or you might have immune system changes due to aging. You also might not be taking the medication as directed. If you take an antihistamine after being exposed to an allergy trigger, it won't work as well.
ZYRTEC® Allergy Dye-Free Chewables
Adults and children 6 years and older Chew and swallow 2 tablet (10 mg) once daily; do not take more than 1 tablet (10 mg) in 24 hours. A 5 mg product may be appropriate for less severe symptoms.
Tolerance developed to one antihistamine extended to others, even though the chemical relationship was not close. 4. 4. Return of pharmacologic response to an antihistamine after discontinuance of the drug takes from 3 to 14 days.
If you have seasonal allergies and notice that your allergy medicine stops working, it might be because you've developed new allergies. People rarely develop a tolerance to allergy medications. Common medications like Zyrtec, Allegra, Flonase, and Claritin don't usually stop working.
Since both medications have a common core chemical structure, Zyrtec and Xyzal generally have the same level of effectiveness, onset of action, and range of allergy symptoms treated. Xyzal is slightly less drowsy, so if drowsiness is an issue with your allergy medicine, Xyzal is better than Zyrtec.
When a person stops taking their medication, their body will produce more histamine to make up for the lack of antihistamine. This results in extreme itching. It's common for someone who's addicted to an antihistamine to scratch until they're raw and bleeding.
Mechanism of Injury. The cause of acute liver injury from cetirizine is not known. It is metabolized by the liver and a toxic metabolite may account for idiosyncratic injury.
Cetirizine is the most potent antihistamine available and has been subjected to more clinical study than any other.
“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.”
If you take too much ZYRTEC you may be more likely to have side effects such as: confusion, diarrhoea, dizziness, tiredness, headache, malaise, dilating of pupil, itching, restlessness, sedation, somnolence (feeling drowsy), stupor, abnormal rapid heart rate, tremor, urinary retention.
What's the best time of day to take ZYRTEC®? Any time of day works. And ZYRTEC® will continue to work for 24 hours.
Louis report that allergens in the environment often are to blame for episodes of acute itch in eczema patients, and that the itching often doesn't respond to antihistamines because the itch signals are being carried to the brain along a previously unrecognized pathway that current drugs don't target.
Is it safe to use antihistamines every day? In general, most of the available over-the-counter antihistamines are safe for long-term use. There are some potential side effects and there are some cases where long-term antihistamine use can worsen urinary retention or narrow angle glaucoma.
Some medications for treating allergies, like Zyrtec (cetirizine) and Allegra (fexofenadine) last 24 hours and don't need to be taken at night. But if you're combating allergy symptoms with a different antihistamine first thing in the morning, keep in mind that its effects will only last six to eight hours.
Claritin and Zyrtec are effective and safe for most people with minor allergies.
by Drugs.com
The elimination half-life of Zyrtec is between 8 to 9 hours. It takes approximately 5.5 x elimination half-life for a medicine to be cleared from your system. For Zyrtec this is 5.5 x 9 hours which is about 2 days.
Antihistamines
Antihistamines are known to cause extreme drowsiness; however, in certain people, they can cause insomnia, excitability, anxiety, restlessness, and a rapid heart rate.