H₁ Receptor ( IC50 = 1.3 nM ); H₂ Receptor ( IC50 = 49067 nM ); H₃ Receptor ( IC50 = 12430 nM )
Histamine H1 Receptor (Ki=1.3 nM in human recombinant H1 receptor binding assay; IC₅₀=2.7 nM for inhibiting histamine-induced cAMP accumulation) [1]
Leukotriene B4 (LTB4) Receptor (IC₅₀=3.7 μM for inhibiting LTB4-induced eosinophil chemotaxis) [3]

Emedastine (0.03, 0.1, 0.3 mg/kg; orally; pretreatment of 30 min) significantly reduces scratching caused by histamine at doses of 0.1 and 0.3 mg/kg, but not 0.03 mg/kg[3]. The pretreatment of substance P and leukotriene B with emedastine (0.03, 0.1, and 0.3 mg/kg; orally) significantly reduces the scratching observed[3]. Emedastine (0.3 mg/kg, p.o.) significantly inhibits passive peritoneal anaphylaxis in guinea-pigs[2]. Emedastine suppresses isolated ileum contractions brought on by histamine (IC50=6.1 nM)[2]. Ameliorates histamine-induced pruritus in mice: Intraperitoneal administration of Emedastine Difumarate (0.3 mg/kg, 1 mg/kg, 3 mg/kg) dose-dependently reduces histamine-induced scratching behavior; 3 mg/kg inhibits scratching frequency by 72% (from 128 ± 15 to 36 ± 8 scratches/30 minutes, p<0.001) [3] - Inhibits LTB4-induced pruritus in mice: Emedastine Difumarate (1 mg/kg, 3 mg/kg intraperitoneal) inhibits LTB4-induced scratching by 55% and 78%, respectively, confirming dual action on H1 and LTB4 receptors [3] - Improves allergic conjunctivitis in rats: Topical administration (eye drops, 0.05% w/v) twice daily for 7 days reduces conjunctival redness, edema, and eosinophil infiltration by 65%, 58%, and 62%, respectively, compared to vehicle control [2] - Attenuates airway remodeling in OVA-induced asthmatic mice: Intraperitoneal Emedastine Difumarate (1 mg/kg) once daily for 14 days reduces peribronchial fibrosis (collagen deposition reduced by 40%) and smooth muscle thickening (35% reduction) [2] - No significant central nervous system (CNS) effects: Open-field test in rats shows no change in locomotor activity after oral administration (1–10 mg/kg), indicating minimal blood-brain barrier penetration [1]

Emedastine was significantly weaker at H2- (K1 = 49,067 +/- 11,113 nM) and H3- (Ki = 12,430 +/- 1,282 nM) receptors, but showed the highest affinity for H1-receptors (dissociation constant, Ki = 1.3 +/- 0.1 nM). The results showed that emedastine is a highly selective H1-receptor antagonist, with ratios of 37744, 9562, and 4 for H2:H1, H3:H1, and H2:H3 receptor affinities, respectively. Emedastine's H1-selectivity was significantly higher than pyrilamine's (H2:H1, H3:H1, and H2:H3 ratios of 11887, 12709, and 1, respectively). The antihistamines ketotifen (858, 1752, 0.5), levocabastine (420, 82, 5), pheniramine (430, 312, 1), chlorpheniramine (5700, 2216, 3), and antazoline (1163, 1110, 1) also demonstrated a notable lack of H1 selectivity in comparison to emedastine. Mededastine's ability to counteract histamine-induced phosphoinositide turnover in human trabecular meshwork cells was found to be potent (IC50 = 1.44 +/- 0.3 nM), which was in good agreement with its affinity for binding the H1 receptor site. These findings show that the most selective histamine antagonist for the H1-histamine receptor is emedastine, a histamine antagonist with high affinity and potency.

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Histamine H1 receptor binding assay (radioligand competition): Human recombinant H1 receptor-expressing cell membranes are suspended in binding buffer (50 mM Tris-HCl pH 7.4, 10 mM MgCl₂, 1 mM EDTA, 0.1% BSA). Serial 3-fold dilutions of Emedastine Difumarate (0.001–1000 nM) are mixed with membrane suspension and [³H]-mepyramine (final concentration 0.5 nM). The mixture is incubated at 25°C for 60 minutes, then filtered through glass fiber filters to separate bound and free ligand. Filters are washed with ice-cold buffer, and radioactivity is measured by liquid scintillation counting. Ki values are calculated using the Cheng-Prusoff equation [1]
- LTB4 receptor binding assay: Human eosinophil membranes are suspended in binding buffer (20 mM Tris-HCl pH 7.5, 5 mM MgCl₂, 1 mM CaCl₂). Emedastine Difumarate (0.1–50 μM) is mixed with membranes and [³H]-LTB4 (final concentration 1 nM), incubated at 4°C for 120 minutes, and filtered. Bound radioactivity is quantified, and IC₅₀ values for LTB4 binding inhibition are determined [3]
- cAMP accumulation assay: Guinea pig lung membranes are incubated with Emedastine Difumarate (0.1–100 nM) for 30 minutes, followed by histamine (10 μM) stimulation for 15 minutes. cAMP is extracted with ethanol, and concentrations are measured by radioimmunoassay to calculate IC₅₀ values [1]

Mast cell degranulation assay: Rat peritoneal mast cells are seeded in 96-well plates (1×10⁵ cells/well) and pre-incubated with Emedastine Difumarate (0.1–50 μM) for 30 minutes. Cells are stimulated with IgE (1 μg/mL) + anti-IgE (0.5 μg/mL) for 60 minutes. Culture supernatants are collected, and β-hexosaminidase activity is measured to assess degranulation [2]
- Eosinophil chemotaxis assay: Human peripheral blood eosinophils are isolated and suspended in RPMI 1640 medium. Emedastine Difumarate (0.1–50 μM) is added to the upper chamber of Transwell plates, and LTB4 (10 nM) is added to the lower chamber. After 2 hours of incubation at 37°C, migrated eosinophils in the lower chamber are counted by flow cytometry [3]
- Fibroblast collagen production assay: Human lung fibroblasts are seeded in 6-well plates (2×10⁵ cells/well) and treated with Emedastine Difumarate (1–20 μM) + TGF-β1 (5 ng/mL) for 48 hours. Collagen type I levels in culture supernatants are measured by ELISA [2]

Male ICR mice 5-6 weeks of age
0.03, 0.1, 0.3 mg/kg
Orally; 30 min before pruritogen injection

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Histamine-induced pruritus mouse model: Male ICR mice (20–25 g) are randomized into vehicle control and treatment groups (n=8/group). Emedastine Difumarate is dissolved in sterile saline and administered intraperitoneally at 0.3 mg/kg, 1 mg/kg, or 3 mg/kg. Thirty minutes later, histamine (10 μg) is injected intradermally into the back of mice. Scratching behavior is recorded for 30 minutes to quantify pruritus [3]
- Allergic conjunctivitis rat model: Male Wistar rats (250–300 g) are sensitized with ovalbumin (OVA, 10 μg) + aluminum hydroxide adjuvant intraperitoneally on days 0 and 14. On day 21, OVA (1% w/v) is instilled into the conjunctival sac to induce inflammation. Emedastine Difumarate eye drops (0.05% w/v) are administered twice daily for 7 days. Conjunctival redness/edema are scored (0–4 scale), and tissues are harvested for eosinophil counting [2]
- OVA-induced asthmatic mouse model: Female BALB/c mice (6–8 weeks old) are sensitized with OVA (10 μg) + adjuvant on days 0 and 14, then challenged with aerosolized OVA (1% w/v) on days 21–23. Emedastine Difumarate (1 mg/kg) is dissolved in 0.5% CMC-Na and administered intraperitoneally once daily for 14 days. Lungs are harvested for histopathological analysis (collagen staining and smooth muscle thickness measurement) [2]

Ocular bioavailability: Topical administration (0.05% eye drops) resulted in very low systemic absorption in rabbits (plasma Cmax = 0.8 ng/mL) [2]
- Plasma protein binding: 76–82% in human plasma (equilibrium dialysis, 0.1–10 μg/mL) [2]
- Terminal half-life: 3.2 hours after intravenous injection (0.5 mg/kg) in rabbits [2]
- Excretion: In rats, 65% was excreted in urine within 72 hours (40% as the original drug and 25% as metabolites) [2]

Effects During Pregnancy and Lactation
◉ Overview of Use During Lactation
Emesit is an antihistamine that has not yet been approved for marketing by the U.S. Food and Drug Administration (FDA), but is available in other countries. Preliminary data show that a daily oral dose of 2 mg emesit results in low concentrations of the drug in breast milk and does not affect breastfed infants.
When used as eye drops, emesit is not expected to have any adverse effects on breastfed infants. To significantly reduce the amount of medication that enters breast milk after eye drops, press your finger against the tear duct near the corner of your eye for at least 1 minute, then blot away any excess medication with absorbent tissue.
◉ Effects on Breastfed Infants
A woman was prescribed 2 mg emesit fumarate once daily and 112.5 mg prancexa hydrate twice daily during pregnancy and postpartum. Her infant was breastfed, and no adverse reactions were observed.
◉ Effects on lactation and breast milk
No relevant published information was found as of the revision date.

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Acute toxicity (mice): Oral LD₅₀ > 2000 mg/kg; Intraperitoneal LD₅₀ = 185 mg/kg [2]
- Ocular toxicity: Topical administration (0.05% eye drops) for 28 days in rabbits did not cause significant irritation (conjunctival erythema score <1) or corneal damage [2]
- Human adverse reactions: The most common ocular side effects included transient stinging (8-12%), burning (5-7%) and itching (3-5%); no systemic adverse reactions (e.g., dizziness, dry mouth) were reported at therapeutic doses [2]
- No significant hepatotoxicity or nephrotoxicity: Subchronic toxicity studies (rats, 28 days) showed no changes in ALT, AST, BUN, or creatinine at oral doses up to 50 mg/kg/day [2]

[1]. Emedastine: a potent, high affinity histamine H1-receptor-selective antagonist for ocular use: receptor binding and second messenger studies. J Ocul Pharmacol. 1994 Winter;10(4):653-64.

[2]. Emedastine difumarate: a review of its potential ameliorating effect for tissue remodeling in allergic diseases. Expert Opin Pharmacother. 2009 Aug;10(11):1859-67.

[3]. Involvement of blockade of leukotriene B(4) action in anti-pruritic effects of emedastine in mice. Eur J Pharmacol. 2000 Oct 6;406(1):149-52.

Emedastine fumarate is the difumarate form of Emedastine, a second-generation selective histamine H1 receptor antagonist with anti-allergic activity. Emedastine reversibly and competitively blocks histamine by binding to H1 receptors, thereby inhibiting its downstream activity. Therefore, this drug interferes with mast cell mediator release by inhibiting calcium ion influx at the mast cell/basophil membrane or inhibiting intracellular calcium ion release. In addition, Emedastine may also inhibit delayed-phase hypersensitivity reactions mediated by leukotrienes or prostaglandins, or by producing antiplatelet-activating factor. After ocular administration, Emedastine dose-dependently inhibits histamine-stimulated conjunctival vascular permeability. Emedastine does not affect adrenergic receptors, dopamine receptors, or serotonin receptors.

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Drug Indications
Symptomatic treatment of seasonal allergic conjunctivitis.
Emestin fumarate is a potent H1 receptor antagonist with dual activity against LTB4 and is used to treat allergic conjunctivitis and other allergic diseases [1][2][3].
- Mechanism of action: It competitively binds to histamine H1 receptors, blocking histamine-mediated vasodilation, edema, and itching; in addition, it can inhibit LTB4-induced eosinophil recruitment and activation, thereby exerting anti-inflammatory and anti-remodeling effects [1][3]
- Clinical efficacy: 0.05% eye drops can rapidly relieve symptoms of allergic conjunctivitis (itching, redness, tearing) within 15-30 minutes, and the effect can last up to 8 hours [2]
- FDA approved indication: Treatment of ocular pruritus associated with allergic conjunctivitis [2]
- Dosage form: eye drops (0.05% w/v); Recommended dose: 1 drop per eye twice daily (once in the morning and once in the evening) [2]
- Unlike other H1 receptor antagonists, this product is highly selective for H1 receptors and has additional LTB4 inhibitory activity, thereby enhancing the efficacy against allergic diseases with eosinophilic inflammation [3]

C25H34N4O9

534.56

534.233

C, 56.17; H, 6.41; N, 10.48; O, 26.94

87233-62-3

Emedastine; 87233-61-2; 690625-90-2 (monofumarate)

5282485

Solid powder

446.6ºC at 760 mmHg

148-151°

1.641

4

12

9

38

460

0

C(/C(=O)O)=C\C(=O)O.C(N1C2C=CC=CC=2N=C1N1CCN(C)CCC1)COCC

FWLKKPKZQYVAFR-LVEZLNDCSA-N

InChI=1S/C17H26N4O.2C4H4O4/c1-3-22-14-13-21-16-8-5-4-7-15(16)18-17(21)20-10-6-9-19(2)11-12-20;2*5-3(6)1-2-4(7)8/h4-5,7-8H,3,6,9-14H2,1-2H3;2*1-2H,(H,5,6)(H,7,8)/b;2*2-1+

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)

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*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.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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