Usage
Desloratadine is prescribed for the relief of symptoms associated with:
- Seasonal allergic rhinitis (hay fever): Sneezing, runny nose, itchy nose/throat/eyes, and watery eyes.
- Perennial allergic rhinitis (year-round allergies): Similar symptoms to seasonal allergies but occurring throughout the year.
- Chronic idiopathic urticaria (hives): Itchy, raised welts on the skin.
Pharmacological Classification: Desloratadine is a second-generation antihistamine, specifically an H1-receptor antagonist.
Mechanism of Action: Desloratadine works by selectively blocking the peripheral histamine H1 receptors. This inhibits the actions of histamine, a chemical mediator released during allergic reactions, reducing the associated symptoms. It is considered “non-sedating” because it does not readily cross the blood-brain barrier.
Alternate Names
Desloratadine is the generic name.
Brand Names: Aerius, Clarinex, Clarinex RediTabs, and various generic formulations.
How It Works
Pharmacodynamics: Desloratadine effectively antagonizes the effects of histamine at peripheral H1 receptors, mitigating the symptoms of allergic reactions. It exhibits minimal anticholinergic and sedative properties.
Pharmacokinetics:
- Absorption: Desloratadine is well absorbed after oral administration, reaching peak plasma concentrations in approximately 3 hours. Food intake may slightly delay absorption, but it does not affect overall bioavailability.
- Metabolism: Desloratadine is extensively metabolized in the liver, primarily by CYP2D6 and to a lesser extent by CYP3A4. It is metabolized to its active metabolite 3-hydroxydesloratadine.
- Elimination: Desloratadine and its metabolites are eliminated through both renal and hepatic pathways. The elimination half-life is approximately 27 hours, which allows for once-daily dosing.
Mode of Action: Desloratadine competitively binds to peripheral H1 receptors, preventing histamine from binding and triggering the downstream signaling cascade responsible for allergic symptoms.
Receptor Binding/Enzyme Inhibition: Desloratadine selectively targets H1 receptors. Its metabolism involves CYP2D6 and CYP3A4 enzymes.
Dosage
Standard Dosage
Adults and Adolescents (12 years and older): 5 mg orally once daily.
Children:
- 6 to 11 years: 2.5 mg orally once daily.
- 1 to 5 years: 1.25 mg orally once daily.
- 6 to 11 months: 1 mg orally once daily.
- Under 6 months: Use is not recommended.
Special Cases:
- Elderly Patients: Start with a lower dose (2.5 mg) and adjust as needed based on tolerability and clinical response.
- Patients with Renal Impairment: A starting dose of 5 mg every other day is recommended.
- Patients with Hepatic Dysfunction: A starting dose of 5 mg every other day is recommended.
- Patients with Comorbid Conditions: Careful monitoring is advised, and dose adjustments may be necessary depending on the specific comorbidity.
Clinical Use Cases
Desloratadine is not typically indicated for use in acute clinical settings like intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations. It primarily manages chronic allergic conditions.
Dosage Adjustments:
Dose adjustments may be required based on age, renal function, and hepatic function as outlined above. Genetic polymorphisms affecting CYP2D6 activity can influence desloratadine metabolism, but routine genetic testing is not typically recommended.
Side Effects
Common Side Effects:
- Fatigue
- Dry mouth
- Headache
- Pharyngitis
- Myalgia
Rare but Serious Side Effects:
- Allergic reactions (rash, itching, swelling, difficulty breathing)
- Seizures (rare, especially in children)
Long-Term Effects:
No significant long-term adverse effects have been reported with desloratadine use.
Adverse Drug Reactions (ADR):
Severe allergic reactions (anaphylaxis) are rare but require immediate medical intervention.
Contraindications
- Hypersensitivity to desloratadine or loratadine.
Drug Interactions
- CYP3A4 and CYP2D6 Inhibitors: Ketoconazole, erythromycin, azithromycin, fluoxetine, and cimetidine may increase desloratadine plasma concentrations. Monitor closely and consider dosage adjustments.
Pregnancy and Breastfeeding
- Pregnancy: Desloratadine is classified as Pregnancy Category C. Use only if the potential benefit justifies the potential risk to the fetus.
- Breastfeeding: Desloratadine is excreted in breast milk. Weigh the benefits of breastfeeding against the potential risk to the infant. Consider using an alternative medication or temporarily discontinuing breastfeeding.
Drug Profile Summary
- Mechanism of Action: Selective peripheral H1-receptor antagonist.
- Side Effects: Fatigue, dry mouth, headache, pharyngitis, myalgia. Rarely, allergic reactions and seizures.
- Contraindications: Hypersensitivity to desloratadine or loratadine.
- Drug Interactions: CYP3A4 and CYP2D6 inhibitors (e.g., ketoconazole, erythromycin).
- Pregnancy & Breastfeeding: Use with caution. Category C. Excreted in breast milk.
- Dosage: Adults and adolescents: 5 mg once daily. Children: Dose varies by age (see above).
- Monitoring Parameters: Monitor for efficacy and adverse events, especially allergic reactions.
Popular Combinations
Desloratadine is often used as monotherapy. However, it can be combined with intranasal corticosteroids for more comprehensive management of allergic rhinitis when symptoms are not adequately controlled with desloratadine alone.
Precautions
- General Precautions: Assess for any history of hypersensitivity reactions.
- Specific Populations: Caution in patients with renal or hepatic impairment, history of seizures (especially children), pregnant or breastfeeding women.
- Lifestyle Considerations: Although considered non-sedating, some individuals may experience mild drowsiness. Advise patients to avoid operating machinery or driving until they know how the medication affects them.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Desloratadine?
A: Adults and adolescents (12 years and older): 5 mg orally once daily. Children: Dose varies by age (see detailed dosage section above).
Q2: How does Desloratadine differ from other antihistamines?
A: Desloratadine is a second-generation antihistamine considered non-sedating because it has limited penetration into the central nervous system.
Q3: Can Desloratadine be taken with food?
A: Yes, desloratadine can be taken with or without food.
Q4: What should I do if I miss a dose?
A: Take the missed dose as soon as you remember. If it is almost time for the next dose, skip the missed dose and return to your regular dosing schedule. Do not double the dose to catch up.
Q5: What are the common side effects of Desloratadine?
A: Common side effects include fatigue, dry mouth, headache, and sore throat.
Q6: Can Desloratadine be used during pregnancy?
A: Desloratadine is a Pregnancy Category C drug. Consult with a doctor to assess the risks and benefits before using during pregnancy.
Q7: How long does it take for Desloratadine to start working?
A: Desloratadine typically starts working within 1-3 hours after taking a dose.
Q8: Can I take Desloratadine with other medications?
A: Some medications can interact with Desloratadine. Inform your doctor about all other medications, including over-the-counter drugs and supplements, that you are taking.
Q9: What should I do if I experience an allergic reaction to Desloratadine?
A: Stop taking the medication and seek immediate medical attention.
Q10: Is Desloratadine safe for long-term use?
A: Generally, Desloratadine is considered safe for long-term use. However, it’s essential to discuss any concerns with your doctor.
