Desloratadine

Approved Indications:

• Allergic Rhinitis (Seasonal and Perennial): For relief of nasal and non-nasal symptoms such as sneezing, rhinorrhea, nasal congestion, pruritus, and conjunctival symptoms.
• Chronic Idiopathic Urticaria: For the relief of pruritus and reduction in the number and size of hives.

Clinically Accepted Off-Label Uses:

• Atopic Dermatitis (Adjunctive): To help relieve allergic symptoms associated with eczema.
• Allergic Conjunctivitis: In combination therapy with other agents.
• Allergic cough or postnasal drip: Used in practice as supportive treatment.

Route: Oral
Formulations: Tablets, orally disintegrating tablets (ODTs), syrup

Adults and Adolescents ≥12 years:

• 5 mg once daily.

Children 6 to 11 years:

• 2.5 mg once daily (tablet or syrup).

Children 1 to 5 years:

• 1.25 mg once daily (syrup).

Children 6 to 11 months:

• 1.0 mg once daily (syrup).

Elderly:

• No dose adjustment generally required, but caution due to decreased renal function.

Renal or Hepatic Impairment:

• Initial dose: 5 mg every other day. Use with caution due to prolonged elimination half-life.

Administration Tips:

• May be taken with or without food.
• ODT should be placed on the tongue and allowed to dissolve without water.

Desloratadine is a long-acting, non-sedating, selective peripheral H1-receptor antagonist. It works by competitively inhibiting histamine at H1-receptor sites on effector cells in the gastrointestinal tract, blood vessels, and respiratory tract. Unlike first-generation antihistamines, desloratadine does not cross the blood-brain barrier appreciably, minimizing CNS effects such as drowsiness. It also exhibits anti-inflammatory properties by inhibiting the release of cytokines and chemokines from mast cells and basophils, contributing to its effectiveness in allergic conditions.

• Absorption: Rapidly absorbed after oral administration; peak plasma levels in 3 hours.
• Bioavailability: ~10–20% (oral); clinical effect observed within 1 hour.
• Distribution: Volume of distribution ~49 L; plasma protein binding ~83–87%.
• Metabolism: Extensively metabolized in the liver, primarily by hydroxylation to 3-hydroxydesloratadine (active).
• Half-life: ~27 hours.
• Excretion: ~50% in urine and ~50% in feces, primarily as metabolites.

• Pregnancy Category: Not formally assigned (former FDA Category C). Animal studies show no teratogenicity; insufficient human data. Use only if benefits outweigh potential risks.
• Lactation: Desloratadine is excreted in small amounts in breast milk. Use with caution; consider alternative if infant is premature or has health issues.

• Primary Class: Second-generation H1-Antihistamine
• Subclass: Non-sedating selective histamine receptor antagonist

• Known hypersensitivity to desloratadine, loratadine, or any excipients in the formulation.
• Severe renal impairment (relative contraindication without monitoring).

• Hepatic Impairment: Use caution; elimination may be delayed.
• Renal Impairment: Risk of accumulation; dose adjustment necessary.
• Allergic Reactions: Rare cases of anaphylaxis reported.
• CNS Effects: Though rare, mild sedation may occur in some patients.
• Pediatric Use: Approved in infants ≥6 months; safety not established below this age.

Common (≥1%):

• Headache
• Dry mouth
• Fatigue
• Pharyngitis
• Drowsiness (rare for second-generation)

Uncommon to Rare:

• Myalgia
• Dysmenorrhea
• Tachycardia or palpitations
• Increased liver enzymes

Serious (Very Rare):

• Hypersensitivity reactions (urticaria, anaphylaxis)
• Seizures (in isolated pediatric cases)

Most adverse effects are mild and transient.

• Major enzyme: Desloratadine is metabolized by CYP3A4 and CYP2D6, but clinical drug interactions are minimal due to its low hepatic metabolism rate.
• Ketoconazole, erythromycin, azithromycin, fluoxetine, and cimetidine may increase plasma concentration slightly without clinical significance.
• Alcohol: No significant interaction, but CNS effects may be amplified in sensitive individuals.
• Food: No significant food-drug interactions observed.

• Updated clinical practice guidelines support desloratadine as a first-line option for allergic rhinitis and urticaria, particularly in pediatric populations due to its safety profile.
• No recent safety warnings or dosage changes noted.
• EMA and FDA reaffirmed its use in children ≥6 months and emphasized its favorable CNS safety profile.

• Tablets/ODT/Syrup: Store at 20°C to 25°C (68°F to 77°F).
• Excursion limits: 15°C to 30°C.
• Protect from moisture and excessive heat.
• Do not freeze syrup.
• Store in original container and keep tightly closed.