Usage
Ebastine is prescribed for the symptomatic treatment of allergic rhinitis (seasonal and perennial) and chronic idiopathic urticaria. It belongs to the pharmacological classification of second-generation antihistamines. Ebastine works by competitively antagonizing histamine H1 receptors, thus reducing the effects of histamine release in allergic reactions.
Alternate Names
While “ebastine” is the internationally recognized generic name, brand names vary depending on the region. Some popular brand names include Evastin, Ebastel, and Kestine.
How It Works
Pharmacodynamics: Ebastine primarily acts as a selective histamine H1 receptor antagonist in the periphery. It effectively diminishes the vascular permeability and smooth muscle contraction caused by histamine, thereby relieving allergy symptoms.
Pharmacokinetics: Ebastine is rapidly absorbed after oral administration. It’s extensively metabolized in the liver, primarily by CYP3A4, 2J2 and 4F12 enzymes, to its active metabolite, carebastine. Carebastine is responsible for most of the antihistaminic activity. Both ebastine and carebastine have high plasma protein binding (over 95%). Peak plasma concentrations of carebastine are reached in 2.6 to 4 hours. The elimination half-life of carebastine is 15-19 hours, allowing for once-daily dosing. Elimination occurs mainly through renal excretion of conjugated metabolites.
Mode of Action: Ebastine competes with histamine for binding to H1 receptors. This prevents histamine from activating these receptors, thereby inhibiting the downstream effects that lead to allergic manifestations.
Receptor Binding/Enzyme Inhibition: Ebastine and its active metabolite, carebastine, primarily bind to histamine H1 receptors. The parent drug, ebastine, is metabolized by CYP3A4, 2J2 and 4F12 hepatic enzymes. Concomitant administration with CYP3A4 inhibitors (e.g., ketoconazole, erythromycin) can significantly increase plasma concentrations of ebastine and carebastine.
Elimination Pathways: Primarily renal excretion of conjugated metabolites.
Dosage
Standard Dosage
Adults:
10 mg orally once daily. This can be increased to 20 mg once daily for severe symptoms.
Children:
- 6-11 years: 5 mg orally once daily. This can be administered as a syrup.
- 12 years and older: Same as adult dose.
- Under 6 Years: Not established.
Special Cases:
- Elderly Patients: Dosage adjustments are generally not necessary.
- Patients with Renal Impairment: No dose adjustment required for mild, moderate or severe renal impairment.
- Patients with Hepatic Dysfunction: No dose adjustment is required for mild to moderate hepatic impairment. For severe hepatic impairment, the dose should not exceed 10 mg daily.
- Patients with Comorbid Conditions: Exercise caution in patients with known QT interval prolongation, hypokalemia, or those taking medications that prolong the QT interval or are CYP3A4, CYP2J2, or CYP4F12 inhibitors.
Clinical Use Cases
Ebastine is not typically used in clinical settings like intubation, surgical procedures, mechanical ventilation, or ICU, nor emergency situations. Its primary role is in managing allergic rhinitis and chronic urticaria.
Dosage Adjustments
Dosage modifications should be considered based on patient-specific factors, particularly severe hepatic impairment as outlined above.
Side Effects
Common Side Effects:
Headache, drowsiness, dry mouth, nausea, abdominal pain, and fatigue.
Rare but Serious Side Effects:
Allergic reactions (e.g., rash, itching, swelling), severe skin reactions (e.g., Stevens-Johnson syndrome), QT interval prolongation (rarely), and liver dysfunction.
Long-Term Effects:
Long-term effects of ebastine are generally not observed with recommended dosages. However, continuous monitoring for any unusual or persistent side effects is advised during prolonged use.
Adverse Drug Reactions (ADR):
Clinically significant ADRs are rare but can include angioedema, anaphylaxis, and severe skin reactions. These necessitate immediate medical intervention.
Contraindications
Hypersensitivity to ebastine. Use with caution in patients with a prolonged QT interval or those taking QT-prolonging drugs.
Drug Interactions
- CYP3A4 Inhibitors: Ketoconazole, erythromycin, and other CYP3A4 inhibitors can increase ebastine plasma levels.
- QT Prolonging Drugs: Concomitant use with other QT prolonging drugs can increase the risk of QT prolongation.
Avoid grapefruit juice, which may inhibit CYP3A4. No clinically significant interactions have been reported with theophylline, warfarin, cimetidine, diazepam, or alcohol.
Pregnancy and Breastfeeding
Pregnancy: Use not recommended due to insufficient data.
Breastfeeding: Use not recommended due to unknown excretion in breast milk.
Drug Profile Summary
- Mechanism of Action: Selective peripheral H1 receptor antagonist.
- Side Effects: Headache, drowsiness, dry mouth, nausea. Rarely: allergic reactions, QT prolongation.
- Contraindications: Hypersensitivity to ebastine. Caution in patients with prolonged QT.
- Drug Interactions: CYP3A4 inhibitors, QT prolonging drugs.
- Pregnancy & Breastfeeding: Not recommended.
- Dosage: Adults: 10-20mg daily; Children (6-11 years): 5mg daily; Children (12 years and over): 10-20 mg.
- Monitoring Parameters: Monitor for allergic reactions and, in at-risk patients, QT interval.
Popular Combinations
Ebastine is not typically used in combination with other medications for its main indications.
Precautions
- General Precautions: Assess for pre-existing conditions, especially cardiac conditions or hepatic dysfunction.
- Specific Populations: As described in “Special Cases” under Dosage.
- Lifestyle Considerations: Caution patients about possible drowsiness and its impact on driving or operating machinery.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Ebastine?
A: Adults: 10-20 mg once daily. Children (6-11 years): 5 mg once daily. Children (12 years and over): 10-20 mg.
Q2: How does Ebastine work?
A: It blocks the action of histamine by antagonizing H1 receptors.
Q3: What are the common side effects of Ebastine?
A: Headache, drowsiness, dry mouth, and nausea are common.
Q4: Is Ebastine safe during pregnancy or breastfeeding?
A: It’s generally not recommended due to limited safety data.
Q5: Can I take Ebastine with other medications?
A: Some drug interactions can occur. Inform your physician about all medications you are taking, especially azole antifungals and macrolide antibiotics.
Q6: How long does it take for Ebastine to work?
A: Effects are typically noticeable within 1-3 hours, with peak effects in 8-12 hours.
Q7: What should I do if I miss a dose of Ebastine?
A: Take the missed dose as soon as you remember, unless it is almost time for your next dose. Do not double the dose.
Q8: Can Ebastine be used for skin allergies?
A: Yes, it is indicated for chronic idiopathic urticaria, a skin condition with allergic components.
Q9: Is Ebastine a sedating antihistamine?
A: It’s considered a non-sedating or low-sedating antihistamine, meaning it is less likely to cause drowsiness compared to first-generation antihistamines. However, some individuals may still experience mild drowsiness.
