No, Dasergin (cetirizine) and Opexa (bilastine) are not the same—bilastine offers comparable efficacy with significantly less sedation.
Key Differences Between These Antihistamines
Both drugs are second-generation H1-antihistamines with similar overall efficacy for allergic conditions, but bilastine has a superior safety profile, particularly regarding sedation 1, 2, 3.
Efficacy Comparison
Allergic Rhinitis: Bilastine 20 mg and cetirizine 10 mg demonstrate comparable efficacy in reducing total symptom scores, nasal symptoms, and non-nasal symptoms 2. Both drugs significantly outperform placebo in treating seasonal allergic rhinitis.
Chronic Spontaneous Urticaria: Bilastine shows greater efficacy than cetirizine in reducing mean total symptom scores, with earlier onset of action (significant improvement at 1 week vs. 3 weeks for cetirizine) 1.
Onset of Action: Bilastine has a faster onset—achieving >70% inhibition of histamine-induced wheal and flare responses at 1.5 hours in 92% of patients versus only 27% with cetirizine 4.
Duration: Both maintain 24-hour efficacy, though bilastine demonstrates sustained action beyond 26 hours 5.
Critical Safety Distinction
The most clinically significant difference is sedation risk:
- Bilastine causes somnolence in only 1.8% of patients 2
- Cetirizine causes somnolence in 7.5% of patients (P<0.001) 2
- This difference is consistent across multiple studies 3, 6
Cetirizine is noted in guidelines as "may be sedating, especially at higher doses" 7, while bilastine maintains its non-sedating profile even when up-dosed 8.
Clinical Implications
For patients requiring antihistamine therapy:
- Choose bilastine when sedation would impair daily function (driving, operating machinery, work performance)
- Choose bilastine for chronic spontaneous urticaria requiring faster symptom control 1
- Either drug is acceptable for allergic rhinitis when sedation is not a concern
- Bilastine is preferred for up-dosing (up to 4x standard dose) as it maintains non-sedating properties, whereas cetirizine shows dose-dependent sedation risk 8
Dosing
- Bilastine: 20 mg once daily
- Cetirizine: 10 mg once daily (may require dose adjustment in renal impairment—halve dose in moderate impairment) 7
Common Pitfall
Don't assume all second-generation antihistamines are equivalent. While efficacy may be similar, the sedation profile differs substantially and should guide drug selection based on patient lifestyle and occupation.