Comparative inhibition by oral bilastine, parenteral dexchlorpheniramine, and a new bilastine parenteral (i.v. and i.m.) formulation of histamine-induced wheal and flare response: A randomised phase I trial

Background: Bilastine is a well-known non-sedating second-generation antihistamine authorised worldwide for the symptomatic treatment of allergic rhinoconjunctivitis (seasonal and perennial) and urticaria with proven efficacy and good safety and tolerability profile. When the oral route is not suitable or a rapid onset of action is preferred, parenteral formulations represent an effective treatment option. However, the parenteral formulations currently available are sedating antihistamines. The objective of this research was to compare the peripheral anti-H₁ activity of different bilastine formulations (i.v., i.m. and oral) and dexchlorpheniramine among them also versus placebo.

Methods: This was a single-dose, randomized, crossover, double-blind, placebo-controlled, phase I clinical study performed on 25 adult healthy volunteers that compared the peripheral antihistaminic activity of a single dose of bilastine 12 mg i.v., bilastine 12 mg i.m., bilastine 20 mg oral tablets and dexchlorpheniramine 5 mg i.m. among them and versus placebo by inhibiting the histamine-induced wheal and flare (W&F) response. Pharmacokinetics, safety, and tolerability were also evaluated.

Results: All bilastine formulations showed a rapid onset of action (15 min for parenteral and 30 min for the oral formulation), and the maximum effect in both wheal (i.v. 74.44 %; i.m.:74.29 %; oral 70,27 %) and flare area reduction (i.v. and i.m. 80.63 %; oral 77.67 %), was significantly larger compared to dexchlorpheniramine i.m. (25.85 % for wheal and 28.65 % for flare) and placebo (1.35 % for wheal and 4.02 % for flare). A more pronounced reduction in itching score was reached for bilastine oral, followed by i.m. and i.v. formulations. No serious adverse events (SAEs) were reported during the study, and 8 treatment-emergent adverse events (TEAEs) were reported by 5 subjects, all resolved without sequelae. For psychomotor assessments, dexchlorpheniramine i.m. showed a fast onset of drowsiness, as well as decreased attention and coordination when compared to all bilastine formulations and placebo.

Conclusions: All bilastine formulations showed a peripheral H₁-blocking effect inducing a significantly greater inhibition of the wheal and flare response as compared to dexchlorpheniramine i.m. or placebo and provided a greater reduction of the itching sensation score. This study reconfirmed that bilastine has no sedative effect, even in a parenteral formulation. These results suggest that new bilastine parenteral formulation (i.v. or i.m.) may represent a suitable alternative for patients requiring immediate treatment of histamine-mediated type I hypersensitivity reactions, such as acute urticaria, or in those cases where oral administration is not possible.