What Is Desloratadine (Clarinex)? Uses, Dosage, and What You Need to Know in 2026

Desloratadine — sold under the brand name Clarinex — is a prescription antihistamine used to treat seasonal and year-round allergies and chronic hives. It was first approved by the FDA in 2001 and has been widely used for over two decades. Here's everything you need to know about what it is, what it treats, and how to take it correctly.

What Is Desloratadine?

Desloratadine is a second-generation antihistamine. It belongs to the same drug class as Loratadine (Claritin), Cetirizine (Zyrtec), and Fexofenadine (Allegra), but it requires a prescription in the United States while the others are available over the counter. Desloratadine is actually the active metabolite of Loratadine — it's the compound your body naturally converts Loratadine into after you take Claritin.

Like other second-generation antihistamines, Desloratadine is designed to relieve allergy symptoms without causing significant drowsiness. It blocks histamine — the chemical your body releases during an allergic reaction — before it can cause symptoms.

What Does Desloratadine Treat?

The FDA has approved Desloratadine for three conditions:

Seasonal Allergic Rhinitis (hay fever): Treats nasal and non-nasal symptoms including sneezing, runny nose, itchy and watery eyes, and nasal congestion caused by seasonal allergens like tree, grass, and weed pollens. Approved for patients 2 years and older.

Perennial (Year-Round) Allergic Rhinitis: Treats the same symptoms caused by year-round allergens like dust mites, pet dander, and mold. Approved for patients 6 months and older.

Chronic Idiopathic Urticaria (chronic hives): Reduces itching, the number of hives, and the size of hives. Approved for patients 6 months and older.

What Forms Does Desloratadine Come In?

5 mg film-coated tablet: The most commonly available form. Available as both brand (Clarinex) and generic Desloratadine.

Orally disintegrating tablet (ODT): 2.5 mg and 5 mg doses. Place on tongue and let dissolve — no water needed. The brand-name Clarinex RediTabs have been discontinued; generic ODT versions may be available from some manufacturers.

Oral solution (liquid): 0.5 mg/mL. The brand-name Clarinex Oral Solution has been discontinued; some generic liquid formulations may be available.

How Do You Take Desloratadine?

Take once daily, at the same time each day

Can be taken with or without food — food does not affect absorption

Swallow tablets whole with water

For ODT: peel back the foil, place tablet on tongue immediately, let it dissolve before swallowing (with or without water)

For oral solution: use the provided measuring device — do not use a kitchen spoon

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Desloratadine Dosage by Age

Adults and children 12 years and older: 5 mg once daily

Children 6 to 11 years: 2.5 mg once daily

Children 6 months to 5 years: 1.25 mg once daily (oral solution)

Renal or hepatic impairment (adults): Start at every 48 hours (not daily)

How Long Before Desloratadine Starts Working?

Desloratadine typically starts to work within 1-3 hours of taking your first dose. It can take several days of consistent daily use for the full antihistamine effect to build up, especially for chronic conditions like perennial rhinitis or chronic urticaria. Clinical studies showed the drug exhibits antihistaminic effect by 1 hour, with activity persisting for up to 24 hours.

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Important Safety Information

Do not use if allergic to Desloratadine, Loratadine, or any ingredient in the formulation

Tell your doctor about kidney or liver disease before starting

Tell your doctor if you are pregnant or breastfeeding

The ODT may contain phenylalanine — alert your doctor if you have phenylketonuria (PKU)

Do not increase dose or frequency without medical guidance — higher doses do not increase effectiveness and may cause drowsiness

Is Desloratadine Available Over the Counter?

No — Desloratadine requires a prescription in the United States. This makes it harder to access and more expensive than OTC alternatives. However, for patients who need prescription documentation, have specific clinical reasons for preferring it, or can't tolerate OTC alternatives, it remains a valuable medication.

How to Get Desloratadine

Once you have your prescription, use medfinder to find which pharmacies near you have Desloratadine in stock. For more detailed information on side effects, read our guide: Desloratadine Side Effects: What to Expect and When to Call Your Doctor.