What is Xyzal Allergy 24HR. How does Xyzal compare to other antihistamines. Is Xyzal effective for allergy relief. Can Xyzal cause drowsiness. Where can you purchase Xyzal.

What Is Xyzal and How Does It Work?

Xyzal is a potent antihistamine medication designed to provide relief from various allergy symptoms. Its active ingredient, levocetirizine, works by counteracting the body’s response to allergens. When an allergic individual encounters triggers, their body releases histamines, which are responsible for the uncomfortable symptoms associated with allergies.

Histamines can cause a range of reactions in different parts of the body:

• Eyes: Itching and watering
• Nose: Sneezing, itching, and excess mucus production
• Mouth and throat: Itching and swelling
• Skin: Hives and itching

Xyzal effectively neutralizes these histamines, providing temporary relief from irritating allergy symptoms. It’s particularly noteworthy for its long-lasting effects, offering 24-hour protection against both indoor and outdoor allergens.

Xyzal vs. Other Antihistamines: A Comparative Analysis

Xyzal joins a lineup of well-known over-the-counter antihistamines, including Claritin (loratadine), Allegra (fexofenadine), Zyrtec (cetirizine), and Benadryl (diphenhydramine). Each of these medications has its unique active ingredient, which determines its specific properties and effectiveness.

How does Xyzal stack up against its competitors? Clinical studies have shown that Xyzal provides noticeable allergy symptom relief in under one hour, which is twice as fast as Claritin. Additionally, its effects last for a full 24 hours, outperforming Benadryl by a significant margin.

Key Advantages of Xyzal:

1. Rapid onset of action (under 1 hour)
2. Long-lasting relief (24 hours)
3. Suitable for adults and children over 2 years old
4. Effective against both indoor and outdoor allergens

The Science Behind Xyzal: Understanding Levocetirizine

Levocetirizine is the active ingredient in Xyzal, responsible for its therapeutic effects. It’s crucial to understand that Xyzal is simply a brand name, while levocetirizine is the actual medicine working to alleviate allergy symptoms.

According to the FDA, generic drugs like levocetirizine are designed to be equivalent to their brand-name counterparts in terms of:

• Dosage form
• Safety
• Strength
• Route of administration
• Quality
• Performance characteristics

This means that generic levocetirizine provides the same clinical benefits as brand-name Xyzal, often at a significantly lower cost. The primary difference lies in the marketing and packaging, not the medication’s effectiveness.

Xyzal’s Effectiveness: What Symptoms Does It Treat?

Xyzal is highly effective in providing temporary relief from a wide range of allergy symptoms associated with hay fever and other respiratory allergies. These include:

• Runny nose
• Sneezing
• Itchy, watery eyes
• Itching of the nose or throat
• Other commonly associated allergy symptoms

Its ability to address multiple symptoms simultaneously makes Xyzal a versatile choice for allergy sufferers. The medication’s rapid onset of action and long-lasting effects contribute to its popularity among those seeking reliable allergy relief.

Potential Side Effects: Does Xyzal Cause Drowsiness?

One common concern with antihistamines is their potential to cause drowsiness. In the case of Xyzal, the answer is not straightforward. While levocetirizine, the active ingredient in Xyzal, may cause drowsiness in some individuals, it’s generally considered less likely to do so compared to older, first-generation antihistamines like Benadryl.

Xyzal belongs to a newer generation of antihistamines specifically designed to minimize drowsiness. In clinical studies, only about 6% of users reported experiencing drowsiness when taking Xyzal. This relatively low percentage suggests that for most people, Xyzal is unlikely to cause significant sedation.

Tips for Managing Potential Drowsiness:

• Take Xyzal in the evening before bed if drowsiness is a concern
• Avoid activities requiring alertness until you know how the medication affects you
• Consult your healthcare provider if drowsiness persists or becomes problematic

Availability and Accessibility: Where to Find Xyzal

Prior to 2017, levocetirizine tablets were only available in the United States with a prescription from a doctor. However, in January 2017, the FDA deregulated levocetirizine, allowing it to be sold over-the-counter without a prescription.

Today, levocetirizine is available both as a prescription drug and as an over-the-counter medication. Interestingly, the prescription version and the over-the-counter version of levocetirizine are identical in terms of medicine and strength (5 mg).

Key Points About Xyzal’s Availability:

• Available over-the-counter since 2017
• Prescription and OTC versions are the same strength (5 mg)
• Often more cost-effective to purchase OTC than through prescription
• Widely available in pharmacies and online retailers

Many consumers find that purchasing levocetirizine over-the-counter is not only more convenient but also less expensive than obtaining it through a prescription pharmacy, while still providing the same relief.

Xyzal and Decongestants: Clearing Up Common Misconceptions

A frequent question among allergy sufferers is whether Xyzal is a decongestant. The answer is no, levocetirizine, the active ingredient in Xyzal, is not a decongestant. It’s important to understand the distinction between antihistamines like Xyzal and decongestants.

Antihistamines vs. Decongestants:

• Antihistamines (like Xyzal): Block histamine reactions, reducing allergy symptoms
• Decongestants: Shrink swollen blood vessels in the nasal passages, relieving congestion

While Xyzal is highly effective at treating many allergy symptoms, it may not provide significant relief from nasal congestion. For individuals experiencing severe congestion along with other allergy symptoms, a combination of an antihistamine and a decongestant might be more effective.

Maximizing the Benefits of Xyzal: Usage Tips and Best Practices

To get the most out of your Xyzal treatment, consider the following tips and best practices:

1. Consistency is key: Take Xyzal at the same time each day for optimal effectiveness
2. Stay hydrated: Drink plenty of water to help flush out allergens and maintain overall health
3. Monitor your symptoms: Keep track of which symptoms improve and which persist
4. Be patient: While Xyzal works quickly for many, it may take a few days to reach full effectiveness
5. Consult a healthcare professional: If symptoms persist or worsen, seek medical advice

Remember that while Xyzal is a powerful tool in managing allergies, it’s most effective when used as part of a comprehensive allergy management plan. This may include environmental controls, such as using air purifiers or keeping windows closed during high pollen days.

Combining Xyzal with Other Allergy Treatments:

• Nasal sprays: Can be used in conjunction with Xyzal for additional symptom relief
• Eye drops: May provide targeted relief for itchy, watery eyes
• Natural remedies: Some find relief with saline nasal rinses or local honey (consult your doctor first)

By understanding how to use Xyzal effectively and combining it with other appropriate treatments, you can significantly improve your quality of life during allergy seasons.

The Future of Allergy Treatment: Xyzal’s Role in Ongoing Research

As allergy rates continue to rise globally, medications like Xyzal play an increasingly important role in managing symptoms and improving quality of life for millions of people. Ongoing research into antihistamines and allergy treatments may lead to even more effective formulations or delivery methods in the future.

Current Areas of Research:

• Long-term effects of antihistamine use
• Combination therapies for enhanced symptom relief

li>Personalized medicine approaches to allergy treatment

• Novel drug delivery systems for improved efficacy

While Xyzal and other current antihistamines are highly effective for many people, scientists continue to explore new ways to combat allergies and provide relief to those who may not respond well to existing treatments.

Understanding Allergies: The Role of Xyzal in a Changing Environment

The rise in allergy rates worldwide has been attributed to various factors, including climate change, increased pollution, and changes in lifestyle. As our environment continues to evolve, so too must our approaches to managing allergies.

Xyzal and similar antihistamines represent a crucial line of defense against the increasing prevalence of allergies. However, it’s important to recognize that medication is just one part of a comprehensive approach to allergy management.

Holistic Approaches to Allergy Management:

• Environmental control measures (e.g., air purifiers, allergen-proof bedding)
• Dietary considerations (identifying and avoiding food allergens)
• Stress management techniques (as stress can exacerbate allergy symptoms)
• Regular exercise (which may help boost the immune system)
• Allergy immunotherapy (for long-term desensitization to specific allergens)

By combining the targeted relief provided by medications like Xyzal with broader lifestyle and environmental strategies, individuals can develop a more robust and effective approach to managing their allergies in an ever-changing world.

Navigating Allergy Season: Xyzal as Part of Your Seasonal Strategy

As allergy seasons become more intense and prolonged due to climate change, having a well-planned strategy for managing symptoms is crucial. Xyzal can play a central role in this strategy, providing reliable relief throughout the allergy season.

Seasonal Allergy Management Tips:

1. Start early: Begin taking Xyzal before allergy season peaks to build up protection
2. Monitor pollen counts: Use apps or local weather reports to track allergen levels
3. Adjust outdoor activities: Plan outdoor time when pollen counts are lower
4. Shower after outdoor exposure: Rinse off pollen and other allergens
5. Keep windows closed: Use air conditioning to filter out allergens

By incorporating Xyzal into a comprehensive seasonal allergy plan, you can minimize symptoms and enjoy outdoor activities with greater comfort. Remember to consult with a healthcare professional to develop a personalized strategy that works best for your specific allergy profile.

Xyzal for Different Age Groups: Considerations and Recommendations

Xyzal is approved for use in adults and children as young as 2 years old, making it a versatile option for families dealing with allergies. However, it’s important to consider age-specific factors when using this medication.

Xyzal for Children:

• Dosage may vary based on age and weight
• Liquid formulations are available for easier administration
• Monitor for side effects, which may differ from those in adults
• Consult a pediatrician before starting any new medication

Xyzal for Adults:

• Standard dosage is typically one 5 mg tablet daily
• May be taken with or without food
• Consider potential interactions with other medications
• Discuss with a healthcare provider if pregnant or breastfeeding

Xyzal for Seniors:

• May require dosage adjustments due to age-related changes in metabolism
• Be aware of potential interactions with other medications commonly used by older adults
• Monitor for increased risk of side effects, particularly drowsiness

By tailoring the use of Xyzal to specific age groups and individual needs, patients can maximize its benefits while minimizing potential risks. Always follow the guidance of a healthcare professional when using any medication, including over-the-counter antihistamines like Xyzal.

Xyzal and Lifestyle: Optimizing Allergy Relief in Daily Life

While Xyzal provides effective allergy relief, integrating it into your daily routine and lifestyle can enhance its benefits. Here are some strategies to optimize your allergy management with Xyzal:

Timing Your Dose:

• Take Xyzal at the same time each day for consistent protection
• Consider evening dosing if drowsiness is a concern
• Align dosing with your peak allergy symptoms for maximum relief

Dietary Considerations:

• Xyzal can be taken with or without food
• Stay hydrated to help flush out allergens
• Consider avoiding histamine-rich foods during high allergy periods

Exercise and Physical Activity:

• Xyzal shouldn’t interfere with most physical activities
• Exercise indoors on high pollen days if outdoor allergies are severe
• Shower after outdoor workouts to remove allergens

Travel and Vacation Planning:

• Pack Xyzal in your carry-on for easy access
• Research allergen levels at your destination
• Consider starting Xyzal before traveling to build up protection

By integrating Xyzal into your daily routines and considering how it fits with your lifestyle choices, you can maximize its effectiveness and enjoy greater freedom from allergy symptoms.

What Is Xyzal Allergy 24HR? Compare Xyzal vs Levocetirizine – Curist

by Dr. Marc Goldstein, MD, Curist Allergy Advisor 

Curist delivers FDA-approved medicines to your door at half the price of traditional brands. We hope everyone stays safe and healthy during this time.

You’ve probably heard the names Claritin, Allegra, Zyrtec, and Benadryl, but have you heard of Xyzal (Levocetirizine)? 

For over a decade, an allergy medicine called Xyzal (levocetirizine) has been available by prescription only.  Today, it’s available over-the-counter, and not a minute too soon. With allergies on the rise — 2018 was called “pollengeddon” by some concerned albeit playfully clever experts — it’s important to have as many options readily available when allergy symptoms kick in. 

Xyzal is an oral antihistamine that works for 24 hrs to relieve symptoms of indoor and outdoor allergies.  The way an antihistamine works is by counteracting your body’s response to allergens. When allergic individuals encounter allergens, their bodies release “histamines.”

Histamines are released in the nose, eyes, ears, skin, chest, and GI tract during allergic reactions.  In the eyes, they can cause itching. In the nose, histamines can cause sneezing, itching, and watery mucus in the nose.  In the lips, roof of the mouth, and back of the throat, histamines produce itching and/or swelling. In the skin, they can produce hives.  An antihistamine effectively disarms these particles, and temporarily quells your irritating symptoms.  

Antihistamines that you can purchase over-the-counter include Claritin (loratadine), Allegra (fexofenadine), Zyrtec (cetirizine), and the older standby Benadryl (diphenhydramine).  And now you can add Xyzal (levocetirizine) to the list.

Very simply, levocetirizine is the active ingredient in Xyzal. It’s the medicine that works to improve symptoms.   

What differentiates one antihistamine from another is the active ingredient: the ingredient that is biologically active, i. e. the medicine. It’s that intimidating word on the label that no one knows how to pronounce, in this case ‘levocetirizine’. The name most people are familiar with is the marketing brand used by a drug company to sell the medicine, in this case ‘Xyzal’. So to summarize, Xyzal is the name of a brand which has levocetirizine as its active ingredient.  

According to the FDA:

A generic drug is a medication created to be the same as an existing approved brand-name drug in dosage form, safety, strength, route of administration, quality, and performance characteristics.

Generic medicines work the same as brand-name medicines

A generic medicine works in the same way and provides the same clinical benefit as its brand-name version. This standard applies to all FDA-approved generic medicines. A generic medicine is the same as a brand-name medicine in dosage, safety, effectiveness, strength, stability, and quality, as well as in the way it is taken and should be used.

In more cynical words:

Xyzal = Levocetirizine + Marketing Budget = $ Higher Prices 

For instance, check out Curist levocetirizine for significant savings relative to the brand Xyzal for the same strength medicine.

Levocetirizine temporarily relieves symptoms due to hay fever or other respiratory allergies: 

• runny nose 
• sneezing 
• itchy, watery eyes
• itching of the nose or throat 
• and other commonly associated symptoms

The great thing is that in clinical studies, it provided noticeable allergy symptom relief in under 1 hour — twice as fast as Claritin (loratadine).  It was also found to be just as effective after 24 hours (which beats Benadryl by 6 times). And it is safe for adults and children over 2 years old. 

The answer is maybe, the active ingredient in Xyzal, levocetirizine, may make you drowsy. As a newer generation antihistamine, levocetirizine was designed to reduce drowsiness especially when compared to first generation antihistamines like Benadryl. In studies, only 6% of users experienced drowsiness when taking Xyzal. If you drowsiness is an issue for you when taking levocetirizine, consider taking  in the evening before bed.

Until 2017, levocetirizine tablets were available in the US only by prescription from a doctor. In January 2017, the FDA deregulated levocetirizine and allowed it for sale without a prescription (over-the-counter). Today, levocetirizine is sold both as a prescription drug and as an over-the-counter drug – but because of the deregulation in 2017, the prescription version and the over-the-counter version of levocetirizine are the same medicine at the same strength (levocetirizine 5 mg). In fact, many people find that purchasing levocetirizine over-the-counter is less expensive than through the prescription pharmacy for the same relief.

Levocetirizine, the active ingredient medicine in Xyzal, is not a decongestant. Unlike brand Claritin, where there is a combination pill that includes a decongestant to the original formula (known as Claritin-D), there is not such a combination with Xyzal having a decongestant.  

Finding the right antihistamine for you may take a little bit of trial.  Everyone’s body is unique and responds differently to various allergy medicines. So if other antihistamines have not worked for you (or have stopped working for you), levocetirizine may be a the best alternative to try. Levocetirizine is available at Curist at a fraction of the cost of brand name Xyzal.

To learn more about Xyzal, please visit our Xyzal FAQ page.

About Us | Xyzal® Allergy Relief Medicine

Xyzal

^® vs. Claritin^®

Allergy relief that starts working faster than Claritin^®.*

Xyzal^® and Claritin^® both provide 24 hour allergic rhinitis relief, however, their active ingredients are different. The active ingredient in Claritin^® is loratadine, while Xyzal^® contains levocetirizine, the medicine that provides effective relief starting in one hour.

Xyzal

^® vs. Benadryl^®

Relief that lasts up to 6x longer than Benadryl^®.†

Xyzal^® is made to provide allergy relief that lasts, so you can get a good night’s sleep and have a productive day ahead. In fact, Xyzal^® relieves symptoms up to six times longer than Benadryl^®.^†

Xyzal

^® vs. Zyrtec^®

Smaller allergy tablets with the same relief as Zyrtec^®.‡

Xyzal^® provides the same relief as Zyrtec^® after your first dose. The big difference between them is in the size of the tablet. Xyzal^® is only half the size of Zyrtec^®.^‡ So if you’re looking for a smaller tablet with powerful allergy relief- try Xyzal^®.

Allergy medicine for kids — because little ones need big relief too

Your kiddos can get all-night, all-day allergy relief too. Children’s Xyzal^® Allergy 24HR liquid is designed to relieve tough nighttime allergy symptoms in kids like sneezing, itchy eyes, watery eyes, runny nose, itchy nose, and itchy throat.

Plus, Children’s Xyzal^® comes in two flavors: Grape and Tutti Fruitti

View children’s products

Be wise all, buy Xyzal

^®

Put your tough allergies to bed for all­-night, all-day allergy relief.

View products

Sources

1. https://medlineplus.gov/allergy.html 
2. https://medlineplus.gov/druginfo/meds/a607056.html

*Applies to first dose only.
^†Based on label dosing instructions.
^‡Applies to first dose only. Based on chamber studies and tablet volume.

Allergy during pregnancy and drug.

Alyonka diaper

12 years

No medicine can be considered completely safe when taken during pregnancy. That is why no pregnant woman is willing to participate in drug safety studies.

Therefore, it is only possible to conditionally designate the hazard categories of drugs in the context of their use during pregnancy:
Preparations of Category “ A” are medicines, studies of the effect of which on pregnant women and the fetus, have proven the safety of the drug in the first trimester of pregnancy. A small number of drugs fall into this category, and none of the antiallergic drugs is in Category A.
Products Categories “B” are products that have been studied in pregnant animals. The results of these studies have shown that these medications are relatively safe, but no human studies have been conducted.
Drugs in the “ C” category are drugs that have adverse effects on the fetus in studies in pregnant animals, but the benefits of these drugs may outweigh the potential risk in humans.
Drugs in the “ D” category are drugs for which there is a proven risk, but in some cases the benefit may outweigh the potential risk.
Category “E” drugs are drugs that have been studied in animals and humans. Studies have shown clear signs of birth defects resulting from these drugs, so their use during pregnancy is not recommended.
Antihistamines. Older antihistamines such as chlorpheniramine are preferred in the treatment of allergic rhinitis during pregnancy and are categorized as B. More recent antihistamines such as over-the-counter loratadine (Claritin , generic forms) and cetirizine ( Zyrtec, generic forms) are also category B drugs. One of the most modern category B antihistamines is Xizal (levocetirizine).

Decongestants. Pseudoephedrine (Sudafed®, many generic forms) is the most preferred decongestant used to treat allergies during pregnancy. However, its use should be avoided throughout the first trimester, as this drug can lead to fetal gastroschisis. This drug belongs to category C.

Medical nasal sprays . Nasal Spray Cromilin (NasalCrom) is helpful in the treatment of allergic rhinitis when applied before exposure to an allergen or before allergic symptoms appear. This drug belongs to category B and is available without a prescription. If this does not help, then another steroid nasal drug in category B (all others are in category C ) – budesonide (Rhinocort Aqua) – can serve as a substitute during pregnancy.

Immunotherapy. Antiallergic injections can be continued during pregnancy, but it is not recommended to start these injections during pregnancy. Usually the dose of such injections does not increase during pregnancy, and most allergists even reduce the dose by 50% during this period. Some allergists understand that antiallergic injections should not be canceled during pregnancy, as in this case there is a risk of anaphylaxis and, as a result, the risk of fetal abnormalities. The current research results do not show any other negative effect on the fetus of the antiallergic injections themselves, except for anaphylaxis.

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Xyzal® – the original antihistamine from UCB

The widespread prevalence of allergic diseases (more than 20% of the world’s population) today has turned the problem of allergies into a global medical and social problem. Considering the annual increase in diseases of allergic genesis, noted everywhere (up to 40% of patients in the population, every third inhabitant of the planet suffers from allergic rhinitis and every tenth from bronchial asthma), we can talk about the widespread prevalence of allergies in the world, and that it tends to growth. Studies have shown that over the past 30 years, the prevalence of allergic diseases has doubled every 10 years everywhere. While maintaining the current pace by the middle of the XXI century. almost all adults and children on the planet will have allergic diseases (Luss L.V., 2003).

Therefore, it is not surprising that the appearance on the Ukrainian pharmaceutical market of the original antihistamine drug Xyzal ^® (levocetirizine) from the world leader in the treatment of allergic diseases – the UCB company (Belgium) aroused increased interest of the pharmaceutical community. Roman Babchenko , marketing manager of the pharmaceutical company Schwarz Pharma AG (UCB group of companies), Candidate of Medical Sciences:

— Today, more than 60 trade names of antihistamines are registered in Ukraine. On average, the assortment of a Ukrainian pharmacy contains 5–10 trade names of antihistamine medicines. So what is the relevance of the appearance of another one?

— According to experts, the recent increase in the number of patients with allergic diseases is primarily due to urbanization and scientific and technological progress, due to which humanity is faced with new allergens every day. They are much more aggressive than traditional plant and household allergens, which led to the sensitization of the population a few decades ago. The emergence of new, more aggressive allergens has required the pharmaceutical industry to develop new, more effective antiallergic drugs. The results of clinical studies have shown that Xyzal 9 is a powerful antihistamine drug with proven efficacy superior to some other antiallergic drugs. 0124 ® from UCB (Grant J.A., 2002). Fulfilling its mission, consisting in? “Providing patients with severe diseases with new, more effective drugs” , since April 2009, this company has been supplying the drug Xyzal ^® to Ukraine, thus making the most modern standards of treatment of allergic diseases available to our patients.

Doesn’t it bother you that there are already levocetirizine preparations on the Ukrainian pharmaceutical market, supported by a powerful promotional campaign?

– Yes, indeed, 2 generic drugs of levocetirizine have already been registered in Ukraine. The road to this market has already been paved by two pharmaceutical companies from India – Emcure Pharm, which produces Aleron ^® , which is promoted in Ukraine by Actavis (Iceland), and Kusum Healthcare, the manufacturer of the drug under the trade name L-Cet ^® . I want to note right away that these generic drugs have appeared on the domestic market quite recently, and therefore specialists have not yet accumulated sufficient clinical experience in their use. Therefore, it is important that since 2001, when Xyzal ^® first appeared on the pharmaceutical market, it has been taken by several million patients with allergic diseases worldwide. UCB has already conducted more than 300 clinical studies of this drug, in which a total of more than 75 thousand patients with various manifestations of allergies, of different ages and genders took part.

Xyzal ^® is manufactured in a full cycle plant located in Boule, Switzerland (Fig. 1). We hope that in Ukraine patients with allergies will finally be able to fully experience all the benefits of using Xyzal ^® from UCB.

— Please tell us about the benefits of using Xyzal ^® ?

– The main one, in comparison with other antihistamine drugs, is a more pronounced antiallergic effect (Grant J.A., 2002).

According to the modern understanding of the pathogenesis of allergic diseases, the main cause of the development of allergic symptoms is the release of histamine from mast cells and its interaction with H ₁ -histamine receptors. The main task of antihistamines is to block as many receptors of this type as possible. This is the most important pharmacological characteristic of antihistamines, since the severity of allergic symptoms directly depends on the amount of H ₁ -histamine receptors with which histamine can bind (Gillard M. et al., 2005).

An indicator that determines the proportion of receptors that antihistamines interact with has received the name “occupation of receptors” in pharmacology . Thus, Xyzal ^® has the ability to occupy 90% of H ₁ – histamine receptors 4 hours after application, and after 24 hours – 57% of these receptors. At the same time, the occupation of H1-histamine receptors when using desloratadine preparations after 4 hours after administration is 71%, and after 24 hours – 43% (Gillard M. et al., 2005). That is why the use of levocetirizine allows several times to reduce the severity of the symptoms of allergic diseases, even in patients sensitized by very aggressive allergens (Purohit A., 2003). Occupation H ₁ -histamine receptors while taking other antihistamines is also significantly lower than that of levocetirizine (Gillard M. et al., 2005).

– What is the reason for such a high ability to occupy the largest number of H ₁ histamine receptors in levocetirizine, because the affinity for receptors of this type is higher in desloratadine preparations?

– The strength of drug binding to receptors is determined by their inhibitory constant (affinity constant – K _and ). This indicator is determined in laboratory conditions and characterizes the concentration at which the drug is able to occupy 50% of H ₁ -histamine receptors. The higher K _i , the greater the concentration of the drug content is necessary to occupy 50% of the receptors, and, consequently, the lower the activity of this drug under in vitro conditions.

However, people are not test tubes, the human body is more complicated and it should be remembered that H1-histamine receptor inhibitors are competitive inhibitors of histamine, with which they “compete” for binding to the same binding sites on the surface of the receptors. Therefore, the strength of action of antihistamines depends mainly on the concentration in which these drugs are able to accumulate in the extracellular fluid, where H 9 is located on the cell surface.0198 1 – histamine receptors (Gillard M. et al., 2005) (Fig. 2). Therefore, although the binding strength of desloratadine drugs to histamine receptors is higher than that of levocetirizine (K _i deslorothadine – 0.4 nmol / l, and K _i levocetirizine – 3 nmol / l), this advantage is only relevant in laboratory conditions ( in vitro ). In clinical conditions (in vivo), the ability of levocetirizine to accumulate in localization sites H ₁ -histamine receptors in a significantly higher concentration than desloratadine preparations. Thus, 4 hours after administration, the concentration of levocetirizine in the extracellular fluid is 28 nmol/l, and desloratadine is 1 nmol/l (Gillard M. et al., 2005). That is why the levocetirizine molecule has more opportunities to occupy the H ₁ -histamine receptor and prevent it from connecting with histamine than the desloratadine molecule. The fact is that at the right moment, levocetirizine molecules simply turn out to be much more in the active zone than desloratadine or histamine molecules.

— What can you say about the duration of action of antihistamines? After all, the half-life of desloratadine is longer than that of levocetirizine. It turns out that desloratadine preparations are more effective when taken once?

– With regard to the half-life, which determines the rate of elimination of drugs from the body (but not the duration of their action), despite the fact that this figure for desloratadine is 27 hours, and for levocetirizine – 8 hours, 24 hours after the use of both the concentration of levocetirizine in the extracellular fluid is 4 nmol/l, and desloratadine is only 0. 3 nmol/l. Therefore, the effectiveness of suppressing allergic symptoms by the end of the day while taking Xyzal ^® is significantly higher than with desloratadine (Gillard M. et al., 2005).

– It is known that the UCB company is the developer of another bestseller among antihistamine drugs -? original drug Zyrtec ^® (cetirizine). Tell us about the advantages of using Xyzal ^® compared to cetirizine?

– Xyzal ^® is a stronger antiallergic agent, since cetirizine is a racemate, that is, a mixture of two molecules with mirror-opposite orientation in space: the dextrorotatory isomer – dextrocetirizine and the left-handed isomer – levocetirizine. As shown by the results of a study by UCB, the strength and duration of binding of dextrocetirizine to H ₁ -histamine receptors are lower than those of levocetirizine (Gillard M. et al., 2002). That is, dextrocetirizine is the same competitive inhibitor of histamine as levocetirizine.