Bilastine targets the histamine H₁ receptor (H₁R) as an antagonist. [1][2]
In guinea pig cerebellum membrane binding assays using [³H]-pyrilamine, bilastine has a Ki of 44.15 ± 6.08 nM (pKi = 7.37). For comparison: cetirizine Ki = 143.12 ± 16.35 nM, fexofenadine Ki = 246 ± 40.7 nM. [1]
In human embryonic kidney (HEK) 293 cells stably expressing human recombinant H₁ receptors, bilastine shows an IC50 of 180 nM and a Ki of 64 ± 1.15 nM (pyrilamine reference: IC50 = 2.8 nM, Ki = 1 ± 0.07 nM). [1]
In human pharmacodynamic studies (histamine-induced wheal and flare inhibition), the estimated IC50 (concentration producing 50% inhibition) for wheal effect is 5.15 ng/mL, and for flare effect is 1.25 ng/mL. [2]
Bilastine is a selective histamine H₁ receptor antagonist. Its inhibition constant (Kᵢ) for the H₁ receptor in guinea pig cerebellum is 44.15 ± 6.08 nM, and for the human recombinant H₁ receptor expressed in HEK293 cells, it is 64 ± 1.15 nM [1].
Receptor binding screening at 10 μM showed that bilastine does not significantly bind to 30 other tested receptors, including adrenergic, muscarinic, dopaminergic, serotonergic, and various ion channels and peptide receptors [1].

Bilastine (10 μM) shows no significant displacement of radioligands for 30 different receptors in a receptor binding screening panel, including adenosine A₁/A₂, adrenoceptors (α₁, α₂, β₁, β₂), calcium channel (L-type), dopamine D₁/D₂L, estrogenic, GABA-A, glucocorticoid, glutamate, muscarinic M₂/M₃, opioid (δ, κ, μ), serotonin 5-HT₁/5-HT₂, sigma-1, sodium channel, and testosterone receptors. [1]
Bilastine (10 mM) does not diminish acetylcholine-induced contractions in guinea pig ileum, indicating lack of M₃ antagonist activity. [1]
Bilastine (100 μM) does not significantly shift the concentration-response curve for noradrenaline in rabbit thoracic aorta (α₁-adrenoceptors) or for isoproterenol in guinea pig trachea (β₂-adrenoceptors). [1]
Bilastine (100 μM) lacks significant H₂ antagonist activity: it does not alter the dimaprit-induced positive chronotropic response in guinea pig right atria. [1]
Bilastine (30 μM) does not significantly displace the (R)-α-methyl-histamine concentration-response curve in electrically stimulated guinea pig jejunum, indicating lack of H₃ antagonist activity (pA₂ < 4.5). [1]
Bilastine (30–1000 nM) exhibits concentration-dependent inhibition of ovoalbumin-induced contractions in sensitized guinea pig ileum (Schultz-Dale reaction), with an IC50 of 95.5 nM, indicating anti-inflammatory/anti-anaphylactic activity. Bilastine is 3–8 times more potent than fexofenadine and cetirizine, respectively. [1]

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In H₁ receptor binding studies using guinea pig cerebellum membranes, bilastine inhibited the specific binding of [³H]-pyrilamine in a dose-dependent manner, with a mean Kᵢ of 44.15 ± 6.08 nM [1].
In binding studies using HEK293 cells expressing the human recombinant H₁ receptor, bilastine exerted dose-dependent and specific inhibition of [³H]-pyrilamine binding, with an IC₅₀ of 180 nM and a calculated Kᵢ of 64 ± 1.15 nM [1].
In isolated guinea pig ileum, bilastine exhibited mixed (competitive and non-competitive) antagonism of histamine-induced contractions. It showed competitive behavior up to 33 nM (pA₂ = 8.0) and non-competitive behavior from 100 nM (pD'₂ = 6.2). It was approximately 5.5 times more potent than cetirizine as a competitive antagonist and 10 times more potent as a non-competitive antagonist [1].
In isolated guinea pig trachea, bilastine exhibited non-competitive antagonism of histamine-induced contractions, with a pD'₂ value of 7.1, which was more potent than cetirizine (pD'₂ = 6.3) [1].
In the in vitro Schultz-Dale reaction using sensitized guinea pig ileum, bilastine (30-1000 nM) produced a potent and concentration-dependent inhibition of the contractile response to the antigen ovalbumin, with an IC₅₀ value of 95.5 nM. This anti-anaphylactic activity was 3 to 8 times more potent than fexofenadine and cetirizine, respectively [1].
At a concentration of 100 μM, bilastine did not significantly modify the concentration-response curves induced by serotonin (rat caudal artery), bradykinin (guinea pig ileum), leukotriene D₄ (guinea pig trachea), calcium chloride (depolarized guinea pig ileum), acetylcholine (guinea pig ileum, M₃ receptors), noradrenaline (rabbit thoracic aorta, α₁-adrenoceptors), or isoproterenol (guinea pig trachea, β₂-adrenoceptors), demonstrating a lack of significant antagonism at these receptors [1].
At 100 μM, bilastine lacked significant H₂ receptor antagonist activity in guinea pig right atria, as it did not alter the positive chronotropic effect of the H₂ agonist dimaprit [1].
At 30 μM, bilastine lacked significant H₃ receptor antagonist activity in electrically stimulated guinea pig jejunum, as it did not displace the concentration-response curve of the H₃ agonist (R)-α-methyl-histamine [1].

In healthy subjects, bilastine dose-dependently inhibits histamine-induced skin wheal and flare reactions. Following oral administration, peak plasma concentrations are reached at approximately 1 hour, while maximal pharmacodynamic response is observed later at approximately 4 hours or longer. Using an indirect response pharmacodynamic model (type I: inhibition of response production), the estimated parameters for wheal inhibition are: zero-order rate constant for response production (kin) = 0.44 ng/mL/h, first-order rate constant for response disappearance (kout) = 1.09 h⁻¹, and IC50 = 5.15 ng/mL. For flare inhibition: kin = 11.10 ng/mL/h, kout = 1.03 h⁻¹, and IC50 = 1.25 ng/mL. [2]

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Guinea pig cerebellum H₁ receptor binding: Cerebellum from adult male guinea pigs is homogenized in 50 mM phosphate buffer (pH 7.5) and centrifuged at 30,000g for 10 min at 4°C. The pellet is washed three times and resuspended. Assay tubes contain [³H]-pyrilamine (1 nM final), various concentrations of displacer drugs (bilastine or reference compounds), and membrane suspension (600 μg protein/mL) in a final volume of 1 mL. Non-specific binding is determined with 10 μM astemizole. After incubation for 30 min at 25°C, samples are filtered through GF/B glass filters and counted. Ki values are calculated via IC50 using the Cheng-Prusoff equation. [1]
Human recombinant H₁ receptor binding: HEK293 cells stably transfected with human H₁ receptor are used. Competition assays are performed in duplicate with [³H]-pyrilamine (3 nM final). Non-specific binding is determined with 1 μM cold pyrilamine. Incubation is for 60 min at 22°C. IC50 and Ki values are calculated. [1]
Receptor selectivity screening: A custom panel of 30 receptors is screened. Bilastine (10 μM) is tested for its ability to displace specific radioligands for each receptor. Percentage displacement is calculated. [1]

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Guinea pig ileum H₁ antagonism: Distal ileum fragments (2-3 cm) from adult male guinea pigs are suspended in Tyrode solution at 37°C, oxygenated with carbogen, under 1.2 g resting tension. Histamine cumulative concentration-response curves (10 mM–328 μM) are obtained. Bilastine (30, 100, 300, 1000 nM) is added 30 min before histamine rechallenge. Contractions are recorded isotonically. pA₂ and pD'₂ values are calculated. [1]
Guinea pig trachea H₁ antagonism: Tracheal strips are prepared and mounted in Krebs-Henseleit solution at 37°C with carbogen, under 2 g tension. Histamine cumulative concentration-response curves (0.1 μM–1 mM) are obtained. Bilastine (30, 100, 300 nM) is added 30 min before rechallenge. pD'₂ values are calculated. [1]
Schultz-Dale reaction (sensitized guinea pig ileum): Guinea pigs are immunized with ovoalbumin (1 mg/mL i.p.) on days 1 and 7. After 7–12 days, ileum fragments are exposed to histamine (1 μM) until uniform contractions are recorded. Bilastine (30–1000 nM) is added, then a single contraction with ovoalbumin (0.5 μg/mL) is registered. IC50 values are determined graphically. [1]

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H₁ Receptor Binding in Human Cells: Human embryonic kidney 293 cells stably transfected with the human recombinant H₁ receptor were used. Competition assays were performed in duplicate using [³H]-pyrilamine (3 nM final concentration) as the radioligand. Non-specific binding was determined using 1 μM cold pyrilamine. Cells were incubated for 60 minutes at 22°C. Filter-retained radioactivity was measured in a liquid scintillation counter. IC₅₀ values were determined by nonlinear regression analysis, and Kᵢ values were calculated using the Cheng-Prusoff equation [1].

Guinea pig cerebellum H₁ binding: Adult male guinea pigs (400–600 g) are killed by decapitation; brains are removed, cerebellum dissected, weighed, and frozen at -70°C for later membrane preparation. [1]
Guinea pig ileum and trachea: Adult male guinea pigs are killed by cervical dislocation and exsanguination. Ileum fragments (2-3 cm) or tracheal strips are immediately dissected and placed in organ baths containing oxygenated physiological solution at 37°C. [1]
Sensitized guinea pig ileum (Schultz-Dale): Male guinea pigs are immunized by intraperitoneal injection of 1 mg/mL ovoalbumin solution with aluminum hydroxide saline on days 1 and 7. After 7–12 days, animals are exsanguinated and ileum is removed. [1]
Rat caudal artery (5-HT₂A antagonism): Wistar rats (250–300 g) are sacrificed by asphyxia in CO₂ atmosphere and exsanguinated by carotid artery section. The caudal artery is cannulated with fine wire, and a spiral (~2 cm × 2 mm) is prepared. [1]
Rabbit thoracic aorta (α₁-adrenoceptor antagonism): Rabbit thoracic aorta rings are used. [1]

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Tissue Collection for Ex Vivo Experiments: The study describes numerous protocols for obtaining tissues from animals for ex vivo pharmacological experiments. These include:
Guinea pigs (male, 400-600g) for cerebellum (H₁ binding), ileum (H₁ antagonism, bradykinin antagonism, calcium antagonism, M₃ antagonism, Schultz-Dale reaction), trachea (H₁ antagonism, LTD₄ antagonism, β₂-adrenoceptor antagonism), right atria (H₂ antagonism), and jejunum (H₃ antagonism). Animals were typically killed by decapitation or cervical dislocation [1].
Rats (Wistar, 250-300g) for caudal artery (5-HT₂A antagonism). Animals were sacrificed by asphyxia in a CO₂ atmosphere and exsanguinated [1].
Rabbits (New Zealand, 2-2.5 kg) for thoracic aorta (α₁-adrenoceptor antagonism). Animals were anesthetized and exsanguinated prior to tissue removal [1].

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Tissue Collection for Ex Vivo Experiments: The study describes numerous protocols for obtaining tissues from animals for ex vivo pharmacological experiments. These include:
Guinea pigs (male, 400-600g) for cerebellum (H₁ binding), ileum (H₁ antagonism, bradykinin antagonism, calcium antagonism, M₃ antagonism, Schultz-Dale reaction), trachea (H₁ antagonism, LTD₄ antagonism, β₂-adrenoceptor antagonism), right atria (H₂ antagonism), and jejunum (H₃ antagonism). Animals were typically killed by decapitation or cervical dislocation [1].
Rats (Wistar, 250-300g) for caudal artery (5-HT₂A antagonism). Animals were sacrificed by asphyxia in a CO₂ atmosphere and exsanguinated [1].
Rabbits (New Zealand, 2-2.5 kg) for thoracic aorta (α₁-adrenoceptor antagonism). Animals were anesthetized and exsanguinated prior to tissue removal [1].

Absorption, Distribution and Excretion
The time to peak concentration (Tmax) of Bilastine is 1.13 hours. The absolute bioavailability is 61%. No drug accumulation was observed after 14 days of daily administration of 20-100 mg. Compared to fasting, peak plasma concentration (Cmax) decreased by 25% and 33% when co-administered with a low-fat meal and a high-fat meal, respectively. Co-administration with grapefruit juice reduced Cmax by 30%. Bilastine is primarily excreted in feces (66.5%), with a small amount excreted in urine (28.3%). Almost all of it is excreted unchanged. The total clearance of Bilastine is 9.20 L/h, and the renal clearance is 8.7 L/h. Metabolism/Metabolites Bilastine does not interact with the cytochrome P450 system and is not significantly metabolized in humans.

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Biological half-life
The average elimination half-life is 14.5 hours.

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Bilastine exhibits linear pharmacokinetics over the dose range of 2.5–220 mg. Peak plasma concentration (Cmax) and area under the curve (AUC) increase proportionally with dose. The compound is rapidly absorbed with a first-order absorption rate constant (ka) of 1.50 h⁻¹; peak plasma concentrations are observed approximately 1 hour post-dose. The terminal elimination half-life (t½) is approximately 14 hours. The apparent total body clearance (CL) is 18.1 L/h, central volume of distribution (V₁) is 59.2 L, intercompartmental clearance (Q) is 1.59 L/h, and peripheral volume of distribution (V₂) is 30.2 L. The residual error (proportional) is 28.6%. No accumulation occurs after repeated dosing (accumulation ratio = 1). No significant covariate effects (age, gender, bodyweight, height, serum albumin, creatinine, bilirubin, GGT, AST, BUN, alkaline phosphatase, pulse) are detected on any pharmacokinetic parameter. [2]

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Bilastine exhibits linear pharmacokinetics over a wide dose range from 2.5 to 220 mg/day, as demonstrated by non-compartmental analysis. Both Cmax and AUC increase proportionally with dose [2].
Following oral administration, bilastine is rapidly absorbed, with peak plasma concentrations observed at approximately 1 hour post-dose. The first-order absorption rate constant (ka) is 1.50 h⁻¹ [2].
The pharmacokinetic profile of bilastine is best described by a two-compartment open model with first-order absorption and elimination. Population pharmacokinetic parameter estimates (with relative standard error) are: apparent total body clearance (CL) = 18.1 L/h (1.8%); central volume of distribution (V₁) = 59.2 L (2.2%); intercompartmental clearance (Q) = 1.59 L/h (3.9%); peripheral volume of distribution (V₂) = 30.2 L (5.1%); and ka = 1.50 h⁻¹ (3.2%) [2].
The terminal elimination half-life of bilastine is approximately 14 hours. The drug does not accumulate upon repeated once-daily administration, as the accumulation ratio (AUC at steady state / AUC after a single dose) is approximately 1 [2].
Population pharmacokinetic analysis did not find any significant relationship between the pharmacokinetic parameters of bilastine and the covariates analyzed, which included age, bodyweight, height, sex, serum albumin, creatinine, bilirubin, GGT, AST, BUN, alkaline phosphatase, and pulse rate [2].

Protein Binding
Bilastine binds to human plasma proteins at a rate of 84-90%.
The preclinical study notes that bilastine, unlike first-generation antihistamines, is devoid of sedative effects and, unlike some second-generation antihistamines, is not associated with adverse cardiovascular effects. [1] In human studies, bilastine was well tolerated; no specific adverse event data are presented. [2]

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[1]. Preclinical pharmacology of bilastine, a new selective histamine H1 receptor antagonist: receptor selectivity and in vitro antihistaminic activity. Drugs R D, 2005. 6(6): p. 371-84.

[2]. Pharmacokinetic-pharmacodynamic modelling of the antihistaminic (H1) effect of bilastine. Clin Pharmacokinet, 2009. 48(8): p. 543-54.

Bilastine belongs to the benzimidazole class of drugs. Bilastine is a novel, next-generation antihistamine with high selectivity for H1 histamine receptors, exhibiting rapid onset and long duration of action. Indications: For the relief of nasal and non-nasal symptoms of seasonal rhinitis in patients aged 12 years and older, and for the relief of symptoms of chronic spontaneous urticaria in patients aged 18 years and older. FDA Label: Treatment of allergic conjunctivitis, treatment of acute type I hypersensitivity reactions, treatment of allergic rhinoconjunctivitis, treatment of urticaria, treatment of urticaria, treatment of allergic rhinoconjunctivitis. Mechanism of Action: Bilastine is a selective histamine H1 receptor antagonist (Ki = 64 nM). During an allergic reaction, mast cells degranulate, releasing histamine and other substances. Bilastine reduces allergic symptoms caused by histamine release from mast cells by binding to H1 receptors and preventing their activation.

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Pharmacodynamics
Bilastine is an antihistamine that can relieve allergy symptoms such as nasal congestion and hives.

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Chemical structure and name: Bilastine (2-[4-(2-(4-(1-(2-ethoxyethyl)benzimidazole-2-yl)piperidine-1-yl)ethyl)phenyl]-2-methylpropanoic acid) is a benzimidazole derivative. [1][2]
Mechanism of action: Bilastine acts as a competitive and non-competitive mixed H₁ antagonist. In guinea pig ileum, it shows competitive behavior up to 33 nM and non-competitive from 100 nM (pA₂ = 8.0, pD'₂ = 6.2). [1]
Anti-inflammatory activity: Bilastine inhibits the Schultz-Dale reaction in sensitized guinea pig ileum (IC50 = 95.5 nM), indicating inhibition of mast cell degranulation and mediator release. [1]
PD modeling: The pharmacodynamic effect of bilastine is best described by a type I indirect response model (inhibition of response production), which accounts for the delay between peak plasma concentration and maximal effect. [2]
Dosing regimen: Simulations based on IC50 values (5.15 ng/mL for wheal, 1.25 ng/mL for flare) demonstrate that a 20 mg once-daily dose maintains plasma concentrations above the IC50 for the entire interdose interval for flare effect, and for up to 20 hours for wheal effect. Doses of 5 and 10 mg do not maintain concentrations above the wheal IC50 throughout the 24-hour period. [2]

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Background: Bilastine (F-96221-BM1) is a new antihistamine drug developed by FAES FARMA, SA (Spain). It is intended for the symptomatic treatment of seasonal or perennial allergic rhinitis and chronic idiopathic urticaria. At the time of this publication, it was in Phase III clinical trials [1].
Mechanism of Action: Bilastine is a selective histamine H₁ receptor antagonist. It works by binding to H₁ receptors, thereby blocking the action of histamine, a key mediator in the allergic response. This prevents histamine-induced effects such as smooth muscle contraction, increased vascular permeability, and stimulation of sensory nerves [1].
Selectivity: A key feature of bilastine demonstrated in this study is its high selectivity for the H₁ receptor. It showed poor or no affinity for a wide panel of 30 other receptors, including adrenergic, muscarinic, serotonergic, and histamine H₂ and H₃ receptors, suggesting a low potential for off-target side effects [1].
Anti-inflammatory Properties: In addition to its H₁ antagonist activity, bilastine demonstrated anti-inflammatory properties in the in vitro Schultz-Dale reaction (a model of immediate-type hypersensitivity), inhibiting the antigen-induced contraction of sensitized guinea pig ileum with an IC₅₀ of 95.5 nM. It was more potent than cetirizine and fexofenadine in this model [1].

C28H37N3O3

463.6117

463.283

C, 72.54; H, 8.04; N, 9.06; O, 10.35

202189-78-4

Bilastine-d6;1215358-58-9

185460

White to off-white solid powder

1.2±0.1 g/cm3

639.1±55.0 °C at 760 mmHg

202 °C

340.3±31.5 °C

0.0±2.0 mmHg at 25°C

1.594

5.06

1

5

10

34

641

0

O(C([H])([H])C([H])([H])[H])C([H])([H])C([H])([H])N1C2=C([H])C([H])=C([H])C([H])=C2N=C1C1([H])C([H])([H])C([H])([H])N(C([H])([H])C([H])([H])C2C([H])=C([H])C(=C([H])C=2[H])C(C(=O)O[H])(C([H])([H])[H])C([H])([H])[H])C([H])([H])C1([H])[H]

ACCMWZWAEFYUGZ-UHFFFAOYSA-N

InChI=1S/C28H37N3O3/c1-4-34-20-19-31-25-8-6-5-7-24(25)29-26(31)22-14-17-30(18-15-22)16-13-21-9-11-23(12-10-21)28(2,3)27(32)33/h5-12,22H,4,13-20H2,1-3H3,(H,32,33)

2-[4-[2-[4-[1-(2-ethoxyethyl)benzimidazol-2-yl]piperidin-1-yl]ethyl]phenyl]-2-methylpropanoic acid

Bilastine; 202189-78-4; Ilaxten; 2-[4-[2-[4-[1-(2-ethoxyethyl)benzimidazol-2-yl]piperidin-1-yl]ethyl]phenyl]-2-methylpropanoic acid; Bilastina; trade name: Bilaxten

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~10 mg/mL (~21.57 mM)

Solubility in Formulation 1: 2 mg/mL (4.31 mM) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), suspension solution; with sonication.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2 mg/mL (4.31 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2 mg/mL (4.31 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)