Introduction
Desloratadine is a second-generation, non-sedating antihistamine used primarily for the management of allergic conditions. As the primary active metabolite of loratadine, it is a selective peripheral H1-receptor antagonist with improved potency and reduced central nervous system penetration compared to first-generation antihistamines. Desloratadine was approved by the FDA in 2001 and has since become a mainstay in allergic rhinitis and chronic idiopathic urticaria treatment.
Mechanism of Action
Desloratadine competitively antagonizes histamine at peripheral H1-receptors. By blocking the interaction of histamine with its receptors, it inhibits the histamine-mediated allergic response, including vasodilation, increased vascular permeability, and sensory nerve stimulation. The drug demonstrates high specificity for peripheral H1-receptors with minimal affinity for muscarinic, serotonin, or alpha-adrenergic receptors, contributing to its favorable side effect profile.
Indications
- Perennial allergic rhinitis
- Seasonal allergic rhinitis
- Chronic idiopathic urticaria
- Symptomatic relief of pruritus and reduction of wheals in urticaria
Dosage and Administration
Adults and adolescents (12 years and older): 5 mg orally once daily Pediatric patients (6-11 years): 2.5 mg orally once daily Pediatric patients (12 months-5 years): 1.25 mg orally once daily Pediatric patients (6-11 months): 1 mg orally once daily Renal impairment: Recommended dose is 5 mg every other day for patients with creatinine clearance <30 mL/min Hepatic impairment: Recommended dose is 5 mg every other dayAdministration may occur without regard to meals as food does not significantly affect bioavailability.
Pharmacokinetics
Absorption: Rapidly absorbed with peak plasma concentrations achieved within approximately 3 hours. Bioavailability is approximately 82-89%. Distribution: Mean volume of distribution is approximately 49 L. Protein binding is 82-87%, primarily to albumin and alpha-1-acid glycoprotein. Metabolism: Undergoes extensive metabolism primarily via hydroxylation to 3-hydroxydesloratadine, which is subsequently glucuronidated. The cytochrome P450 system plays a minor role (CYP3A4 and CYP2D6). Elimination: Mean elimination half-life is approximately 27 hours. Excretion occurs equally in urine and feces as metabolites. Less than 2% is excreted unchanged in urine.Contraindications
- Hypersensitivity to desloratadine, loratadine, or any component of the formulation
- Patients with known hypersensitivity reactions to any antihistamines
Warnings and Precautions
- Use with caution in patients with renal or hepatic impairment (dose adjustment required)
- Although classified as non-sedating, somnolence has been reported in some patients
- Use during pregnancy only if clearly needed (Pregnancy Category C)
- Excreted in breast milk - caution advised during breastfeeding
- Not recommended for children under 6 months of age
Drug Interactions
- Erythromycin, ketoconazole: May increase desloratadine concentrations (clinically significant interactions unlikely at recommended doses)
- CNS depressants: Potential additive sedative effects (though minimal with desloratadine)
- P-glycoprotein inhibitors: Potential for increased desloratadine absorption
No clinically significant interactions with azithromycin, fluoxetine, or cimetidine have been observed.
Adverse Effects
Common (≥2%):- Headache (14%)
- Somnolence (5%)
- Fatigue (4%)
- Dry mouth (3%)
- Pharyngitis (2%)
- Dizziness
- Nausea
- Dyspepsia
- Myalgia
- Tachycardia (rare)
- Hypersensitivity reactions (including rash, pruritus, urticaria)
Monitoring Parameters
- Symptom relief and control of allergic manifestations
- Assessment for sedative effects, particularly during initial therapy
- Renal and hepatic function in patients with impairment
- Monitoring for paradoxical excitation in pediatric patients
- Assessment for therapeutic efficacy after 2-3 days of therapy
Patient Education
- Take medication as prescribed, typically once daily
- May be taken with or without food
- Report any persistent drowsiness, dizziness, or palpitations
- Seek medical attention if allergic symptoms are not controlled
- Avoid activities requiring mental alertness until response to medication is known
- Inform healthcare providers of all medications being taken
- Store at room temperature away from moisture and heat
- Do not crush or chew extended-release tablets
References
1. Geha RS, Meltzer EO. Desloratadine: A new, nonsedating, oral antihistamine. J Allergy Clin Immunol. 2001;107(4):751-762. 2. Simons FE. Advances in H1-antihistamines. N Engl J Med. 2004;351(21):2203-2217. 3. Desloratadine prescribing information. U.S. Food and Drug Administration. 4. Horak F, Zieglmayer UP, Zieglmayer R, et al. The effects of desloratadine on symptoms and quality of life in perennial allergic rhinitis. Allergy. 2003;58(12):1284-1289. 5. Ring J, Heinemann A, Ollert M, et al. Desloratadine in the treatment of chronic idiopathic urticaria. Allergy. 2001;56(Suppl 68):28-32. 6. Gupta S, Banfield C, Kantesaria B, et al. Pharmacokinetic and safety profile of desloratadine and fexofenadine when coadministered with azithromycin. J Clin Pharmacol. 2001;41(10):1053-1061.