What it is
Ebastine is a second-generation H1 antihistamine. It is a prodrug: in the liver it is converted into carebastine, its active metabolite, which has a long half-life and is what allows a single daily dose to cover 24 hours.
It is used in allergic rhinitis and urticaria, at 10 or 20 mg once a day depending on severity. It sedates little. Its practical peculiarity is that it depends on CYP3A4: with strong inhibitors of that enzyme its concentration rises and it can prolong the QT interval.
Mechanism of action
It acts through its active metabolite:
- Carebastine selectively blocks peripheral H1 receptors
- It crosses the blood–brain barrier poorly, which is why it sedates little
- Its long half-life allows a single daily dose
At the counter
When to recommend it
- Seasonal or perennial allergic rhinitis
- Urticaria
- Allergy needing the 20 mg dose because of severity, on medical advice
- Patients who prefer a single daily dose
When not to
- Allergy to ebastine
- Severe liver failure
- Treatment with strong CYP3A4 inhibitors (ketoconazole, itraconazole, clarithromycin, erythromycin)
- Known long QT or medicines that prolong it, unless the doctor decides otherwise
Warnings
- Important QT prolongation: with strong CYP3A4 inhibitors or in patients with long QT. Review the medicines before supplying.
- Caution Occasional dry mouth and headache.
- Caution Drowsiness: uncommon, mainly with 20 mg. Check the response before driving.
- Caution CYP3A4 interactions: avoid ketoconazole, itraconazole, clarithromycin and erythromycin.
Pharmacokinetics
- Absorption
- Rapid oral absorption. It is almost completely converted into carebastine during first-pass hepatic metabolism. Carebastine peaks at 2.5–4 hours. It can be taken with or without food.
- Distribution
- Mainly peripheral distribution. Plasma protein binding above 95%.
- Metabolism
- Hepatic, via CYP3A4, into carebastine (active). That is why it interacts with strong inhibitors of that enzyme.
- Elimination
- Mainly renal, as metabolites. Carebastine's half-life is 15–19 hours: one dose a day.
Ebastine vs cetirizine
| Aspect | Ebastine | Cetirizine |
|---|---|---|
| Doses a day | One | One |
| Half-life | Long (carebastine, 15–19 h) | Moderate (8–9 h) |
| Metabolism | Hepatic (CYP3A4): interactions | Minimal: few interactions |
| Sedation | Low | Low (a little more in some people) |
| Kidney failure | No adjustment in most cases | Adjust the dose if severe |
Similar efficacy. The practical difference is in the metabolism: ebastine means checking the medicines (CYP3A4); cetirizine, kidney function.
Self-assessment
Three questions. When you check your answers you will see the explanation for each one.
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Its active metabolite, carebastine, has a long half-life that covers 24 hours with a single daily dose.
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Ebastine is a prodrug: what acts is carebastine, which is eliminated slowly.
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Clarithromycin is a strong CYP3A4 inhibitor. With ebastine it increases its concentration and the risk of QT prolongation: it needs reviewing before continuing.
Training content. It does not replace the summary of product characteristics or clinical judgement.