Desloratadine
Non-sedating antihistamine for allergic rhinitis and urticaria
Desloratadine is a second-generation, non-sedating H1 receptor antagonist (antihistamine) and the active metabolite of loratadine. It was approved in the European Union in 2001 and in the United States in 2002. Desloratadine is more potent than its parent compound loratadine and has a more favourable pharmacokinetic profile, including a longer duration of action allowing once-daily dosing.
Desloratadine is marketed under trade names including Aerius and Desloratadin-ratiopharm. It belongs to the piperidine subclass of antihistamines and provides reliable, 24-hour symptom control for allergic rhinitis and chronic urticaria without the CNS depression associated with first-generation antihistamines.
Mechanism of Action
Desloratadine competitively and selectively blocks histamine H1 receptors on the cell surfaces of airway epithelium, vascular endothelium, and sensory nerve endings. By preventing histamine binding to these receptors, desloratadine inhibits the early allergic response: vasodilation, increased vascular permeability, bronchoconstriction, and stimulation of sensory nerves causing itching and sneezing.
Unlike first-generation antihistamines, desloratadine has minimal penetration of the blood-brain barrier due to its low lipophilicity and active efflux by P-glycoprotein in the CNS. This explains the absence of significant sedation at standard doses. Additionally, desloratadine has anti-inflammatory properties beyond pure H1 antagonism: it inhibits the release of pro-inflammatory cytokines, reduces eosinophil migration, and inhibits expression of adhesion molecules on endothelial cells.
Indications
- Allergic rhinitis: Seasonal (hay fever) and perennial (year-round, e.g. house dust mite, animal dander) — relieves sneezing, rhinorrhoea, nasal and eye pruritus
- Chronic spontaneous urticaria (CSU): Symptomatic relief of pruritus and wheals in chronic idiopathic urticaria
- Acute allergic reactions: Mild to moderate allergic skin reactions; not for anaphylaxis (where epinephrine is first-line)
Dosage and Administration
Adults and adolescents (over 12 years): 5 mg once daily (one 5 mg tablet or 10 ml syrup). Children 6 to 11 years: 2.5 mg (5 ml syrup) once daily. Children 1 to 5 years: 1.25 mg (2.5 ml syrup) once daily. Children 6 to 11 months: 1 mg (2 ml syrup) once daily.
Desloratadine can be taken with or without food at any time of day. Consistent daily dosing at the same time helps maintain stable plasma levels. In patients with severe renal or hepatic impairment, a starting dose of 5 mg every other day is recommended. No dose adjustment is required for the elderly.
Side Effects
Common at standard doses: Headache, dry mouth, fatigue. These effects are generally mild. Fatigue, when reported, is substantially less frequent than with first-generation antihistamines.
Rare: Tachycardia and palpitations (rare at therapeutic doses); hypersensitivity reactions including rash, urticaria, and very rarely anaphylaxis; elevated liver enzymes. In pharmacogenomic studies, approximately 6 to 7 percent of subjects are poor metabolisers of desloratadine and experience higher plasma levels, which may result in slightly more pronounced side effects.
Desloratadine has a very favourable cardiac safety profile. Unlike astemizole and terfenadine (first-generation antihistamines withdrawn from the market), desloratadine does not cause QT prolongation at therapeutic doses.
Interactions
- Erythromycin and ketoconazole: Inhibit metabolism of desloratadine; plasma levels may increase but no clinically significant cardiac or CNS effects have been observed in studies
- Alcohol: No significant pharmacodynamic interaction at standard doses; additive sedation possible at high alcohol doses
- Other CNS depressants: Minimal interaction at therapeutic doses; caution with very large doses or in sensitive individuals
- No significant interactions with most common cardiovascular drugs, antidiabetics, or other frequently used medications
Special Notes
Driving and cognition: At standard doses, desloratadine does not impair driving ability or psychomotor performance in the majority of patients. However, a small minority of patients (including poor metabolisers with higher drug exposure) may experience fatigue. Patients should assess their individual response before driving.
Pregnancy and breastfeeding: Desloratadine is not recommended during pregnancy due to limited human data, although animal studies do not indicate teratogenic potential. It passes into breast milk; use during breastfeeding should be discussed with a healthcare provider.
Comparison with other antihistamines: Desloratadine, cetirizine, levocetirizine, fexofenadine, and bilastine are all second-generation non-sedating antihistamines with comparable efficacy for allergic rhinitis. Choice between them often depends on patient tolerability, individual variation in sedation, and cost.
Related Topics
- Cetirizine — Second-generation antihistamine with mild sedating potential
- Loratadine — Parent compound of desloratadine
- Fexofenadine — Non-sedating antihistamine, minimal CNS penetration
- All active ingredients overview
Frequently Asked Questions
Is desloratadine better than loratadine?
Desloratadine is the active metabolite of loratadine and is approximately 10 to 20 times more potent in vitro. In clinical practice, both are effective for allergic rhinitis. Desloratadine may offer marginally faster onset and slightly more consistent plasma levels. The clinical difference between the two is modest for most patients.
Can desloratadine be taken during the day without causing drowsiness?
Yes. Desloratadine is specifically classified as a non-sedating antihistamine. The vast majority of patients can take it during work hours without impairment. Studies consistently show no significant difference from placebo in psychomotor tests. A small subset of patients may notice mild fatigue, particularly at the start of therapy.
Does desloratadine help with nasal congestion?
Antihistamines including desloratadine are most effective for sneezing, rhinorrhoea, and itching. Nasal congestion (blocked nose) is predominantly driven by nasal vasodilation and mucosal oedema rather than histamine, and may respond less well to antihistamines alone. Nasal corticosteroid sprays are generally more effective for congestion in persistent allergic rhinitis.