- 10 Common Allergy Triggers Slideshow Pictures
- Take the Quiz on Allergies
- Nasal Allergy Relief Products Slideshow
- Claritin vs. Zyrtec comparison
- What are Claritin and Zyrtec?
- What are the uses for Claritin and Zyrtec?
- What are the side effects of Claritin and Zyrtec?
- How should Claritin and Zyrtec be taken (dosage)?
- Which drugs interact with Claritin and Zyrtec?
- Are Claritin and Zyrtec safe to take during pregnancy or while breastfeeding?
Claritin vs. Zyrtec comparison
Claritin (loratadine) and Zyrtec (cetirizine) are part of a family of second-generation antihistamines used for treatment of hay fever allergies and hives. This group of drugs also includes fexofenadine (Allegra) and azelastine (Astelin)
The advantage of Claritin and Zyrtec is they cause less drowsiness than older anti-allergy drugs like Benadryl or hydroxyzine. Cetirizine and loratadine are very similar. Both interact with few other drugs, but the drugs that cause adverse reactions when combined with Claritin are different than the ones that cause bad reactions with Zyrtec.
Another difference is Zyrtec, according to a 2014 study, is also more likely than Claritin to cause drowsiness as a side effect.
What are Claritin and Zyrtec?
Hay fever (allergic rhinitis), hives (urticaria), and pollen-induced asthma are all reactions to histamines released by the body in response to an allergen (dust, pollen, or animal dander). Second-generation antihistamine drugs like Claritin and Zyrtec keep cells from interacting with histamine, thereby preventing allergy symptoms.
Histamine is a relatively simple, nitrogen-based compound manufactured in special white blood cells called mast cells. Histamine is a crucial messenger chemical used for all kinds of important physiological and neurological functions. The function a histamine molecule performs in any given physiological process depends not on the chemical itself, but how cell proteins latch onto and interpret it.
Researchers have identified four different histamine receptor proteins thus far, named H1 through H4. They each kick off drastically different processes when exposed to histamine. A lot of H1 receptor proteins are located on the outer membranes of nerve cells and blood vessel cells in the mucous membranes of the airways and gut - basically any tissue that has exposure to the outside environment. When, for example, pollen stimulates mast cells to release histamine, the histamine molecules latch onto the H1 receptor proteins, which causes capillaries to open, tissue to swell, and membranes to become more permeable to fluid. In people with allergies, the mast cells overreact to allergens and release way too much histamine, causing runny nose, itchy eyes, sneezing, and inflamed airways.
Loratadine and cetirizine are H1 receptor antagonists. This means each molecule of the medication has a shape and chemical properties that make it fit into the H1 receptor, locking out the histamine without kicking off the inflammation reaction.
Older antihistamines like hydroxyzine are blunt instruments compared to second-generation ones like Claritin and Zyrtec. As mentioned before, histamines are crucial for all sorts of neurological functions, including maintaining normal levels of alertness and wakefulness. Older antihistamines helped with allergy symptoms, but they also blocked H1 receptors in the brain, causing drowsiness.
Molecules of loratadine and cetirizine are shaped in such a way they can't fit through the membranes that separate the bloodstream from brain tissue, meaning Claritin and Zyrtec cause less drowsiness that older antihistamines. According to a 2014 study, however, second-generation antihistamines -- Zyrtec especially -- can affect mood and cause daytime drowsiness more often than doctors initially believed. So, just because the newer medications are more precise doesn't mean they're without side effects.
What are the uses for Claritin and Zyrtec?
What are the side effects of Claritin and Zyrtec?
Latest Asthma News
How should Claritin and Zyrtec be taken (dosage)?
The usual dose is 10 mg per day in tablet form for adults and children older than six years of age. The dose for children 2 to 6 years of age is 5 mg per day.
The recommended dose is 5 to 10 mg per day in tablet form, depending on the severity of symptoms.
Which drugs interact with Claritin and Zyrtec?
Erythromycin, cimetidine (Tagamet), and ketoconazole (Nizoral) increase the blood concentration of loratadine by making it harder for the body to break down. This may result in increased side effects.
Theophylline (Theo-Dur, Respbid, Slo-Bid, Theo-24, Theolair, Uniphyl, Slo-Phyllin) reduces the body's ability to breakdown cetirizine by 16%, increasing blood levels of the medication. Drugs that cause drowsiness may add to drowsiness resulting from cetirizine.
Are Claritin and Zyrtec safe to take during pregnancy or while breastfeeding?
No studies exist about the use of Claritin and Zyrtec by pregnant women, but the prevailing theory is the risk is low for the developing fetus. Still, pregnant women should only take either drug under direction of a doctor if allergy symptoms are severe enough to affect daily functioning. Both of these medications are passed on in breast milk in concentrations similar to what they are in the woman's bloodstream at any given time, so either stop breastfeeding or stop taking these allergy medications.
Claritin (loratadine) and Zyrtec (cetirizine) are both second-generation antihistamines. Antihistamies are anti-allergy drugs, and loratadine and cetirizine both are used against hay fever, pollen-induced asthma, and hives. Learn about the side effects, dosage, and pregnancy safety information for Claritin and Zyrtec.
Multimedia: Slideshows, Images & Quizzes
Could I Be Allergic? Discover Your Allergy Triggers
Allergies are an overreaction of the immune system where the body's defenses react to substances such as pollen, food and more....
Out-of-Control Allergy Symptoms: Treatment Relief in Pictures
Learn 10 signs your allergies are out of control. See these surprising allergy symptoms and find out how to get relief for...
Nasal Allergy Attack: Causes, Triggers, Treatments
Nasal allergies are a common problem that affects millions of people. An allergist can recommend the best allergy nasal sprays...
Pictures of Allergy Relief Tips at Home: AC Filters, Electronic Air Cleaners, and More
Learn how a combination of medication, preventing allergens, and allergy relief products can reduce allergy symptoms and help you...
Home Allergy Quiz: Is Your Home Allergy-Proof?
Take this home allergy quiz and test your knowledge on allergens, dust mites, pollens and more to see how allergy-proof your home...
Related Disease Conditions
An allergy refers to a misguided reaction by our immune system in response to bodily contact with certain foreign substances. When these allergens come in contact with the body, it causes the immune system to develop an allergic reaction in people who are allergic to it. It is estimated that 50 million North Americans are affected by allergic conditions. The parts of the body that are prone to react to allergies include the eyes, nose, lungs, skin, and stomach. Common allergic disorders include hay fever, asthma, allergic eyes, allergic eczema, hives, and allergic shock.
Cold, Flu, Allergy Treatments
Before treating a cold, the flu, or allergies with over-the-counter (OTC) medications, it's important to know what's causing the symptoms, which symptoms one wishes to relieve, and the active ingredients in the OTC product. Taking products that only contain the medications needed for relieving your symptoms prevents ingestion of unnecessary medications and reduces the chances of side effects.
Allergy Treatment Begins At Home
Avoiding allergy triggers at home is one of the best ways to prevent allergy symptoms. Controlling temperature, humidity, and ventilation are a few ways to allergy-proof the home. Cleaning, vacuuming, and using HEPA air filters also helps control allergies.
Treatment & Diagnosis
Medications & Supplements
Health Solutions From Our Sponsors
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
V. Katritch, V. Cherezov, and R.C. Stevens
Annual Review of Pharmicological Toxicology; Jan, 2013
"Molecule of the Month: Histamine"
University of Bristol School of Chemistry, 2008
FDA Prescribing Information
"Histamine Compound Summary"
"Loratidine Compound Summary"
"Cetirizine Compound Summary"
"HRH1 histamine receptor H1 [Homo sapiens (human)]"
National Center for Biotechnology Information
"Assessment of the effects of antihistamine drugs on mood, sleep quality, sleepiness, and dream anxiety"
Pinar Guzel Ozdemir, Ayse Serap Karadag, Yavuz Selvi, Murat Boysan, Serap Gunes Bilgili, Adem Aydin, and Sevda Onder
International Journal Of Psychiatry In Clinical Practice, 2014