Rupatadine

MECHANISM OF ACTION

Rupatadine works as a dual-action antihistamine. It selectively blocks histamine H1 receptors, preventing histamine from causing allergic symptoms such as itching, sneezing, and nasal congestion. Additionally, rupatadine inhibits platelet-activating factor (PAF), which contributes to inflammation and allergic reactions. This dual activity helps reduce both immediate and late-phase allergic responses.

PHARMACOKINETICS

Absorption

Rupatadine is rapidly absorbed after oral administration, with peak plasma concentrations typically reached within 0.5 to 1.5 hours. Food intake may slightly delay absorption but does not significantly affect the overall bioavailability of the drug.

Distribution

Rupatadine has a moderate volume of distribution, approximately 1.9–2.5 L/kg, allowing it to distribute effectively into tissues affected by allergic reactions. Its high protein binding helps maintain plasma concentrations while limiting central nervous system penetration.

Metabolism

Rupatadine is extensively metabolized in the liver, mainly by CYP3A4 enzymes. Its metabolism produces both active and inactive metabolites that contribute to its effects. Liver impairment can affect its clearance and may require dose adjustments.

Elimination

Rupatadine and its metabolites are primarily eliminated through urine and feces. The drug has a half-life of approximately 5–6 hours, allowing for once-daily dosing. Impaired liver or kidney function may affect its elimination and require careful monitoring or dose adjustment.

PHARMACODYNAMICS

Rupatadine is a second-generation antihistamine that provides relief from allergic symptoms by blocking histamine H1 receptors and inhibiting platelet-activating factor (PAF). This dual action reduces nasal congestion, itching, sneezing, and skin hives in both the immediate and late-phase allergic responses. Its selective H1 receptor antagonism minimizes sedation compared to first-generation antihistamines, making it suitable for daily use.

ADMINISTRATION

Rupatadine is administered orally in the form of tablets or oral suspension. It is usually taken once daily, with or without food. The dose and duration depend on the patient’s age, weight, and the severity of allergic symptoms, as recommended by a healthcare provider.

DOSAGE AND STRENGTH

Rupatadine is usually prescribed once daily to manage allergic conditions. Adults and adolescents aged 12 years and older typically receive 10 mg, while children aged 6–11 years are given 5 mg, either as an oral suspension or a half tablet. The drug is available in 10 mg tablets for adults and 5 mg formulations for children, allowing flexible dosing based on age and weight.

DRUG INTERACTIONS

Rupatadine is metabolized mainly by CYP3A4, so drugs that inhibit this enzyme, like ketoconazole, erythromycin, or ritonavir, can increase its levels and side effects. Combining rupatadine with other sedating medications or alcohol may enhance drowsiness.

FOOD INTERACTIONS

Rupatadine can be taken with or without food, as food does not significantly affect its absorption or effectiveness.

CONTRAINDICATIONS

Rupatadine is contraindicated in patients with hypersensitivity to rupatadine or any of its ingredients. It should be avoided in individuals with severe liver impairment or long QT syndrome, and caution is advised when used with other medications that affect heart rhythm.

SIDE EFFECTS

• Headache 

• Drowsiness or mild sedation 

• Dry mouth 

• Fatigue 

• Nausea 

• Rare allergic reactions, such as rash or itching 

OVER DOSE

Overdose may cause drowsiness, headache, dizziness, or rapid heart rate. In severe cases, it can lead to central nervous system depression or cardiac effects.

TOXICITY

Rupatadine toxicity is rare but can occur with excessive doses. It may lead to central nervous system effects like severe drowsiness, dizziness, or agitation, and in extreme cases, cardiac disturbances such as palpitations. Management involves supportive care, monitoring of vital signs, and symptomatic treatment until recovery.