Histamine H1 receptor
Histamine H1 receptor [1]

Bepotastine (10, 100, 1000 µM; preincubates for 120 min) reduces the amount of histamine released when treated with A23187, reaching a statistically significant level at 1000 µM[1].
Bepotastine (50 µM; 1 h) inhibits the expression of NGF mRNA in NHEKs[2].

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Bepotastine inhibited leukotriene B4 (LTB4)-induced chemotaxis of guinea pig peritoneal eosinophils in a dose-dependent manner. At 100 μM, chemotaxis was 81.4% of control (P < 0.05); at 1000 μM, chemotaxis was 30.7% of control (P < 0.01). [1]
- Bepotastine inhibited A23187-induced histamine release from rat peritoneal mast cells. At 1000 μM, histamine release was 43.7% of control (P < 0.01). No significant inhibition was observed at 10 or 100 μM. [1]

Bepotastine (10 g/L; eye drop; 3 times at intervals of 20 min in one eye) significantly reduces the infiltration of conjunctival eosinophils induced by PAF[1].
Bepotastine (3 mg/kg; p.o.; once) minimizes scratching to a frequency of 59.0 and a duration of 14.57 seconds, which is nearly identical to the control[3].
Bepotastine (10 mg/kg; p.o.; once) significantly suppresses serum LTB 4 levels to 711.3 pg/mL at 1 h and 858.8 pg/mL at 2 h in NC/Nga mice with a rash[3].

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In passively sensitized guinea pigs (anti-ovalbumin antiserum), topical bepotastine besilate ophthalmic solution (0.1%, 0.3%, 1.0%, 1.5%) dose-dependently suppressed ovalbumin-induced conjunctival vascular hyperpermeability. Inhibition rates: 0.1%: 40.9% (P < 0.01 vs vehicle); 0.3%: 49.4% (P < 0.01); 1.0%: 60.7% (P < 0.01); 1.5%: 72.8% (P < 0.01). [1]
- In the same model, bepotastine besilate 1.0% significantly inhibited extravasated dye (66.6% inhibition, P < 0.01 vs saline), and its effect was significantly superior to levocabastine 0.025% (P < 0.05). Ketotifen 0.05% (78.8% inhibition, P < 0.01) and olopatadine 0.1% (52.6% inhibition, P < 0.01) also showed significant effects. [1]
- In histamine-induced conjunctival vascular hyperpermeability model, bepotastine besilate 1.0% significantly inhibited hyperpermeability (77.6% inhibition, P < 0.01 vs saline), and was significantly more potent than olopatadine 0.1% (60.1% inhibition, P < 0.01). [1]
- In PAF-induced eosinophil infiltration into guinea pig conjunctiva, bepotastine besilate 1.0% significantly suppressed eosinophil peroxidase (EPO) activity (71.0% inhibition, P < 0.01 vs saline). Its effect was significantly greater than ketotifen 0.05% (51.0% inhibition, P < 0.01) and similar to olopatadine 0.1% (75.6% inhibition, not significant vs bepotastine). [1]

Eosinophil peroxidase (EPO) activity assay: Conjunctival tissues were homogenized in 0.5% n-hexadecyltrimethylammonium bromide in phosphate-buffered saline (pH 7.4) and subjected to two freeze-thaw cycles. Homogenates were centrifuged at 3000 rpm for 10 min. Supernatant (50 μL) was incubated with 100 μL of 5 mM o-phenylenediamine dihydrochloride in 50 mM Tris-HCl (pH 8.0) containing 0.005% hydrogen peroxide for 5 min at room temperature. The reaction was terminated by adding 100 μL of 4 M sulfuric acid. Absorbance was measured at 492 nm using a microplate reader. [1]
- Histamine quantification assay: Released and residual histamine amounts were determined by an enzyme-linked immunosorbent assay (ELISA). Total histamine in rat peritoneal mast cells was calculated as the sum of released and residual histamine contents. [1]

Cell Line: RPMCs
Concentration: 10, 100, 1000 µM
Incubation Time: 120 min (preincubate)
Result: Decreased the release of histamine

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LTB4-induced eosinophil chemotaxis assay: Guinea pig peritoneal eosinophils (>90% purity) were pre-incubated with or without test compound at final concentrations of 10, 100, and 1000 μM in HBSS/BSA containing 0.1% ethanol for 20 min at 37°C in 5% CO2. Cell suspension (50 μL, 2×10^5 cells/mL) was added to the upper wells of a 48-well microchemotaxis chamber separated by a polycarbonate filter (5 μm pore). Lower wells contained 25 μL of 0.1 μM LTB4. Incubation was for 90 min at 37°C in 5% CO2. Non-migrated cells were scraped from the upper side of the filter, and migrated eosinophils on the lower side were fixed, stained with Diff-Quick, and counted by light microscopy. Chemotaxis rate was defined as number of migrated eosinophils with treatment divided by that without treatment. [1]
- Histamine release from rat peritoneal mast cells: Purified rat peritoneal mast cells (2×10^4 cells/mL) were mixed with Tyrode’s solution containing 0.2% ethanol with or without test compound (final concentrations 10, 100, or 1000 μM) and pre-incubated for 120 min at 37°C in 5% CO2. Then 10 μL of calcium ionophore A23187 (final concentration 0.01 μM) was added and incubated for 10 min. Reaction was terminated on ice. Cell suspension was centrifuged at 200×g for 8 min at 4°C. Supernatant was collected for released histamine. The pellet was sonicated in Tyrode’s solution, centrifuged at 800×g for 10 min at 4°C, and supernatant collected for residual histamine. Histamine was quantified by ELISA. [1]

Guinea pigs (6-week-old)
10 g/L (1.0% (w/v)) for 10 µL
Eye drop; 3 times at intervals of 20 min (in one eye).

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Antigen-induced conjunctival vascular hyperpermeability in passively sensitized guinea pigs: Guinea pigs (6-week-old) were anesthetized with ketamine/xylazine. They were passively sensitized by subconjunctival injection of 50 μL of anti-ovalbumin antiserum (diluted 1:600) in one eye. 48 hours later, animals were challenged intravenously with ovalbumin (3 mg/kg) and Evans blue dye (20 mg/kg). 30 minutes before antigen challenge, animals received topical instillation of 10 μL of test article or saline. After 30 minutes, animals were euthanized, conjunctiva was excised, and extravasated dye was extracted and quantified by absorbance at 620 nm. [1]
- Histamine-induced conjunctival vascular hyperpermeability: Guinea pigs (5-week-old) were anesthetized. Immediately after intravenous injection of Evans blue dye (20 mg/kg), 50 μL of 0.2% histamine dihydrochloride was injected into the upper conjunctival sac. 30 minutes before histamine injection, animals received topical instillation of 10 μL of test article or saline. After 30 minutes, animals were euthanized, conjunctiva excised, and extravasated dye quantified. [1]
- PAF-induced eosinophil infiltration into guinea pig conjunctiva: Guinea pigs (6-week-old) received topical instillation of 10 μL of test article in one eye three times at 20-minute intervals. 20 minutes after the last instillation, 10 μL of 0.1% PAF was topically applied to the conjunctiva. 6 hours after PAF instillation, animals were euthanized, conjunctiva removed, and eosinophil peroxidase activity was determined as an index of eosinophil infiltration. [1]

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Antigen-induced conjunctival vascular hyperpermeability in passively sensitized guinea pigs: Guinea pigs (6-week-old) were anesthetized with ketamine/xylazine. They were passively sensitized by subconjunctival injection of 50 μL of anti-ovalbumin antiserum (diluted 1:600) in one eye. 48 hours later, animals were challenged intravenously with ovalbumin (3 mg/kg) and Evans blue dye (20 mg/kg). 30 minutes before antigen challenge, animals received topical instillation of 10 μL of test article or saline. After 30 minutes, animals were euthanized, conjunctiva was excised, and extravasated dye was extracted and quantified by absorbance at 620 nm. [1]
- Histamine-induced conjunctival vascular hyperpermeability: Guinea pigs (5-week-old) were anesthetized. Immediately after intravenous injection of Evans blue dye (20 mg/kg), 50 μL of 0.2% histamine dihydrochloride was injected into the upper conjunctival sac. 30 minutes before histamine injection, animals received topical instillation of 10 μL of test article or saline. After 30 minutes, animals were euthanized, conjunctiva excised, and extravasated dye quantified. [1]
- PAF-induced eosinophil infiltration into guinea pig conjunctiva: Guinea pigs (6-week-old) received topical instillation of 10 μL of test article in one eye three times at 20-minute intervals. 20 minutes after the last instillation, 10 μL of 0.1% PAF was topically applied to the conjunctiva. 6 hours after PAF instillation, animals were euthanized, conjunctiva removed, and eosinophil peroxidase activity was determined as an index of eosinophil infiltration. [1]

Absorption, Distribution and Excretion
Following a single ophthalmic dose, the time to peak concentration (Tmax) is 1.2 hours; the peak concentration (Cmax) for a 1.5% ophthalmic dose is 7.3 ± 1.9 ng/mL. 24 hours after implantation, Bepotastine concentrations are below the limit of quantitation (LOQ) of 2 ng/mL. Systemic absorption of the ophthalmic formulation is minimal. Following oral administration of 2.5–40 mg Bepotastine, 75%–90% of the dose is excreted unchanged in the urine within 24 hours. Metabolism/Metabolites Primarily metabolized by CYP enzymes. Biological Half-Life Elimination half-life = 2.5 hours.

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Absorption: Intestinal absorption was high (70–85%) in rats, dogs, and humans. Regional difference in rat intestine: highest permeability in upper small intestine, decreasing in descending part [4]

- Oral administration in rats (3 mg/kg): Cmax in blood = 0.27 μg Eq/ml, tmax = 0.5 h, t1/2 = 3.0 h (1–8 h), AUC(0-8h) = 0.87 μg Eq/h/ml, AUC(8-24h) = 23.5 μg Eq/h/ml, AUC(0-24h) = 1.38 μg Eq/h/ml [4]

- Oral administration in dogs (0.3 mg/kg): blood (male): Cmax = 0.18 μg Eq/ml, tmax = 1.7 h, t1/2 = 2.9 h (4–8 h), AUC(0-24h) = 1.39 μg Eq/h/ml; plasma (male): Cmax = 0.17 μg Eq/ml, tmax = 1.3 h, t1/2 = 2.9 h (4–8 h), AUC(0-24h) = 1.38 μg Eq/h/ml; blood (female): Cmax = 0.15 μg Eq/ml, tmax = 2.7 h, t1/2 = 4.7 h (8–24 h), AUC(0-24h) = 1.25 μg Eq/h/ml; plasma (female): Cmax = 0.14 μg Eq/ml, tmax = 2.7 h, t1/2 = 3.2 h (4–8 h), AUC(0-24h) = 1.23 μg Eq/h/ml [4]

- Intravenous administration in rats (3 mg/kg): Cmax in blood = 2.04 μg Eq/ml reached by 2 min; AUC(0-8h) = 1.69 μg Eq/h/ml (about twice the oral AUC over same period) [4]

- Distribution: Brain concentration lower than plasma after IV administration in rats, predicting reduced sedation. Bepotastine is a P-glycoprotein substrate (higher brain concentration in P-gp knockout mice) [4]

- Tissue distribution in rats: radioactivity highest in gastric/intestinal contents, then liver, renal cortex; by 24 h highest in intestinal contents, liver, bladder; by 72 h only in melanin-containing tissues [4]

- Repeated dosing (21 days) in rats: steady-state reached after 17th dose; highest radioactivity in liver and kidneys, lowest in cerebellum, eyes, fat, seminal vesicles, testes [4]

- Plasma protein binding: in vivo rat 44–60%, dog 45–56%; in vitro human 60–65%; binding was low avidity and reversible (>95%) [4]

- Metabolism: No significant metabolites in plasma up to 6 h after oral dose in rats and dogs (parent drug ~95% of radioactivity). In rat bile, parent drug ~55%, taurine conjugate ~13%, glucuronide of hydroxyl piperidine metabolite ~11% [4]

- Excretion: Rats (oral): 42% urine, 37% bile, 6% feces over 24 h; total 94% after 120 h; no respiratory excretion. Dogs (oral): 67–69% urine, 22% feces by 24 h; total 95.5% (male) or 97.8% (female) after 120 h, minimal biliary excretion [4]

- Transfer to fetus and milk: In pregnant rats, fetal liver levels similar to maternal plasma; other fetal tissues 1/3 to 1/10 of maternal plasma. In lactating rats, milk Cmax = 0.40 μg Eq/ml at 1 h; milk levels 1.2–2.3 times higher than maternal plasma [4]

Effects During Pregnancy and Lactation
◉ Overview of Use During Lactation
There are currently no reports of mothers breastfeeding their infants while receiving Bepotastine treatment. Due to limited absorption of Bepotastine through the eyes, no adverse effects are expected on breastfed infants. After using eye drops, to significantly reduce the amount of medication entering breast milk, press the tear duct at the corner of the eye for at least 1 minute, then blot away excess medication with absorbent tissue.
◉ Effects on Breastfed Infants
As of the revision date, no published information was found regarding Bepotastine. In a telephone follow-up study, mothers reported irritability and colic in 10% of infants exposed to various antihistamines, and lethargy in 1.6% of infants. All adverse reactions were non-medical, and none of the patients were using Bepotastine.
◉ Effects on Lactation and Breast Milk
Higher doses of antihistamines can lower baseline serum prolactin levels in non-lactating women and early postpartum women. However, pre-administration of antihistamines by postpartum mothers does not affect lactation-induced prolactin secretion. Prolactin levels in established lactating mothers are unlikely to affect their lactation capacity. Low-dose ophthalmic Bepotastine is unlikely to have the same effect on serum prolactin.

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Protein Binding
After oral administration of 10 mg, the mean plasma protein binding rate was 55.4%. The degree of protein binding was independent of plasma drug concentration.

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CNS effects: No sedation, no thiopental or barbital anesthesia enhancement, no convulsion enhancement, no caging-climbing behavior, no change in body temperature in mice at oral doses up to 300 mg/kg. No hypomotility or disruption of huddling at ≤300 mg/kg. Mild mydriasis at 300 mg/kg (1–5 h post-dose). No effect on spontaneous motor activity or hexobarbital-induced sleeping time [4]

- Respiratory and circulatory: No effect on blood pressure, heart rate, or respiratory rate in anesthetized rats at 100 and 300 mg/kg intragastric. In isolated perfused guinea pig hearts: no effect on contractility, heart rate, or coronary blood flow at 10–300 mg/heart; at 1000 mg/heart: decreased contractility 30%, decreased heart rate 5%, increased coronary blood flow 5%. Minimal effects on myocardial membrane currents at 10 μM in guinea pig myocardium [4]

- Digestive system: No effect on gastric emptying or small intestine transit in mice at 100 and 300 mg/kg oral. No effect on gastric fluid volume, acid concentration, or excretion volume in rats at 30–300 mg/kg intragastric [4]

- Urinary system: No effect on urine/electrolyte excretion in rats at 100 mg/kg oral [4]

- Metabolic: No effect on blood sugar or plasma free fatty acids in rats at single dose. No effect on coagulation or fibrinolytic markers after 5 daily doses of 30–300 mg/kg in rats. No effect on platelet aggregation at 10 or 30 μg/ml; slight inhibition of collagen-induced aggregation at 100 μg/ml [4]

- Dogs: IV bepotastine besilate (30 mg/kg) transiently increased renal blood flow; recovery within minutes; no effect at 10 mg/kg [4]

- Rat subacute (4-week) toxicology: NOAEL = 100 mg/kg/day; toxic symptoms at 600 mg/kg/day (26-week) or 1000 mg/kg/day (4-week) including mydriasis, salivation, suppressed body weight gain, decreased food consumption, decreased urine pH, increased calcium, decreased triglyceride, induction of liver enzymes. Liver hypertrophy and increased liver weight observed. NOAEL for chronic (26-week) = 20 mg/kg/day [4]

- Dog toxicology: Vomiting at 200 and 600 mg/kg/day (4-week) and at 100 and 300 mg/kg/day (26-week). No effect on food consumption, ophthalmic exam, respiratory rate, body temperature, blood pressure, urinary tests, ECG, hematology, blood biochemistry, liver enzymes, necropsy, organ weight, or histopathology. Mild transient body weight suppression. NOAEL: 60 mg/kg/day (4-week), 30 mg/kg/day (26-week) [4]

- Reproductive toxicology in rats: NOAEL for parent general toxicity = 40 mg/kg/day; for reproductive capacity = 200 mg/kg/day. At 1000 mg/kg/day: reduced corpora lutea, decreased implantations, increased pre-implantation loss. No embryo deaths, fetal growth inhibition, or teratogenicity at up to 1000 mg/kg/day during organogenesis. Perinatal/postnatal: reduced survival, growth delay, functional inhibition in offspring at 1000 mg/kg/day; NOAEL = 100 mg/kg/day for parent reproductive capacity and fetuses [4]

- Reproductive toxicology in rabbits: Hematuria at 100 and 500 mg/kg/day. Fatalities and birth/suckling disruption at 1000 mg/kg/day. No abnormalities in fetuses up to 500 mg/kg/day. NOAEL for general toxicity = 20 mg/kg/day; for reproductive function and fetuses = 500 mg/kg/day [4]

[1]. Bepotastine besilate, a highly selective histamine H(1) receptor antagonist, suppresses vascular hyperpermeability and eosinophil recruitment in in vitro and in vivo experimental allergic conjunctivitis models. Exp Eye Res. 2010 Jul;91(1):8.

[2]. Bepotastine besilate downregulates the expression of nerve elongation factors in normal human epidermal keratinocytes. J Dermatol Sci. 2018 Apr 23:S0923-1811(18)30186-5.

[3]. Oral administration of bepotastine besilate suppressed scratching behavior of atopic dermatitis model NC/Nga mice. Int Arch Allergy Immunol. 2008;145(4):277-82.

[4]. Non-clinical pharmacology, pharmacokinetics, and safety findings for the antihistamine bepotastine besilate. Curr Med Res Opin. 2010 Oct;26(10):2329-38.

Bepotastine is an ether compound with the chemical name (S)-(4-chlorophenyl)(pyridin-2-yl)methanol, in which the hydroxyl hydrogen is replaced by a 1-(3-carboxypropyl)piperidin-4-yl group. It is a topical, selective, non-sedating histamine (H1) receptor antagonist, used in benzyl sulfonate form to treat itching caused by allergic conjunctivitis. It is both an H1 receptor antagonist and an antihistamine. It belongs to the Pyridalyl, monocarboxylic acid, piperidine, ether, and monochlorobenzene classes. It is the conjugate base of Bepotastine (1+). Bepotastine is a non-sedating, selective histamine 1 (H1) receptor antagonist. Bepotastine was approved in Japan in July 2000 and January 2002 for the treatment of allergic rhinitis and urticaria/pruritus, respectively, and is marketed by Tanabe Pharmaceutical Co., Ltd. under the brand name Talion. In Japan, it is available in oral and ophthalmic formulations. Bepreve ophthalmic solution was approved by the U.S. Food and Drug Administration (FDA) on September 8, 2009. Bepreve is a histamine-1 receptor antagonist. Indications: For the treatment of itchy eyes caused by IgE-induced mast cell degranulation in allergic conjunctivitis. FDA Label: Mechanism of Action: Allergic conjunctivitis occurs due to a type I hypersensitivity cascade triggered by antigen exposure. Upon contact with an allergen, conjunctival mast cells degranulate and form complementary IgE cross-links on the conjunctiva, releasing histamine. Histamine release leads to symptoms such as itching. Bepreve relieves itchy eyes through three main mechanisms of action. It is a non-sedating, selective histamine 1 (H1) receptor antagonist, a mast cell stabilizer, and inhibits the migration of eosinophils to inflamed tissues, thus preventing tissue damage and exacerbation of allergic conjunctival inflammation.

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Pharmacodynamics
Bepotastine is a non-sedating, selective histamine 1 (H1) receptor antagonist. It belongs to the second-generation piperidine class of compounds. It is a mast cell stabilizer and inhibits the migration of eosinophils to inflamed tissues. Furthermore, Bepotastine does not interact with serotonin receptors, muscarinic receptors, benzodiazepine receptors, or β-adrenergic receptors, therefore it does not cause adverse reactions such as dry mouth or drowsiness. Onset of action = 0.25 hours; duration of action = 12-24 hours.

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Bepotastine besilate is a second-generation histamine H1 receptor antagonist possessing high binding selectivity to its receptor and low liability of sedative adverse effects. [1]
- It possesses antiallergic activity due to effects on multiple allergen effector pathways, including inhibition of eosinophil infiltration induced by PAF and antigens in the airway, inhibition of interleukin-5 production by human peripheral blood mononuclear cells, and suppression of LTB4-dependent allergic response. [1]
- Oral bepotastine was reported to inhibit scratching behavior induced by compound 48/80 in mouse models and atopic dermatitis in NC/Nga mice, and to inhibit histamine-induced vascular permeability and homologous passive cutaneous anaphylaxis. [1]
- The drug acts as an inhibitor of allergic response through multiple mechanisms: histamine H1 receptor antagonism, mast cell stabilization, and inhibition of eosinophil migration to ocular inflammatory sites. [1]

C21H25CLN2O3

388.8878

388.155

C, 64.86; H, 6.48; Cl, 9.12; N, 7.20; O, 12.34

125602-71-3

Bepotastine besilate; 190786-44-8; Bepotastine tosylate; 1160415-45-1; 125602-71-3

164522

Light brown to brown liquid

1.3±0.1 g/cm3

546.8±50.0 °C at 760 mmHg

56-58 °C

284.5±30.1 °C

0.0±1.5 mmHg at 25°C

1.605

3.67

1

5

8

27

449

1

C1=CC=NC(=C1)[C@H](C2=CC=C(C=C2)Cl)OC3CCN(CCCC(=O)O)CC3

YWGDOWXRIALTES-NRFANRHFSA-N

InChI=1S/C21H25ClN2O3/c22-17-8-6-16(7-9-17)21(19-4-1-2-12-23-19)27-18-10-14-24(15-11-18)13-3-5-20(25)26/h1-2,4,6-9,12,18,21H,3,5,10-11,13-15H2,(H,25,26)/t21-/m0/s1

4-[4-[(S)-(4-chlorophenyl)-pyridin-2-ylmethoxy]piperidin-1-yl]butanoic acid

TAU-284; TAU 284; TAU284; Bepotastine band name: Talion; Bepreve

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

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

DMSO: 78~100 mg/mL (200.6~257.1 mM)
Water: ~78 mg/mL
Ethanol: ~78 mg/mL

Solubility in Formulation 1: ≥ 2.5 mg/mL (6.43 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% 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 25.0 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: ≥ 2.5 mg/mL (6.43 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 25.0 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: ≥ 2.5 mg/mL (6.43 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 25.0 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.)