COX-3
COX-3 (IC50 = 102 μM in presence of 30 μM arachidonic acid) [1]

Phenacetin was more potent at inhibiting COX-3 than was acetaminophen. Under substrate conditions of 30 μM, phenacetin inhibited COX-3 at an IC50 value of 102 μM, as opposed to 460 μM for acetaminophen tested under similar conditions. As with acetaminophen, phenacetin preferentially inhibited COX-3[1].

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Phenacetin inhibited COX-3 activity in insect cell expression system with an IC50 of 102 μM at 30 μM arachidonic acid, while showing no significant inhibition of COX-1 or COX-2 at concentrations up to 1,000 μM (IC50 >1,000 μM for both). [1]

The effects of long-term smoking on pharmacokinetic profiles of phenacetin in rats are presented in Table 2. Mean plasma concentration-time curves of phenacetin in smoking group and control group are presented in Figure 1A. The results showed that after pretreated with long-term smoking, the AUC(0-∞), t1/2, and Cmax of phenacetin in smoking group were decreased significantly by 32%, 64%, and 27% (P<0.05) compared to those of control group, CL of phenacetin in smoking group was increased significantly by 35% (P<0.05), which indicated that CYP1A2 activity was induced by long-term smoking in rats.[2]

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The animal experiment results showed that baicalin (450 mg/kg, i.v.) significantly decreased the Cmax and CL of phenacetin, and increased C(60 min), t1/2, Vd and AUC (P<0.05). There were significant correlations between percentage of control in C(60 min), t1/2, CL, AUC of phenacetin and Cmax of baicalin in 11 rats (P<0.05). Protein binding experiments in vitro showed that baicalin (0-2000 mg/L) increased the unbound phenacetin from 14.5% to 28.3%. In conclusion, baicalin can inhibit the activity of CYP1A2 in HLMs and exhibit large inter-individual variation that has no relationship with gene polymorphism. Baicalin can change the pharmacokinetics of phenacetin in rats[3].

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Effects of baicalin treatment on phenacetin pharmacokinetics Pharmacokinetics of phenacetin: The plasma concentration versus time profile of phenacetin obtained in the pharmacokinetic studies was given in Figure 3A. This clearly illustrated that the concentration of phenacetin was too low to be detectable at 90 min after administration in control, while it was still (0.12±0.02) mg·L−1 in rats treated with baicalin. As shown in Table 4, baicalin (450 mg/kg, i.v.) was found to significantly decrease the Cmax and CL of phenacetin, and increase C60 min, t1/2, Vd and AUC (P<0.05). The AUC and C60 min of phenacetin in control were (140.2±14.7) mg/L·min and (0.27±0.14) mg/L compared with (162.8±21.1) mg/L·min and (0.55±0.17) mg/L in rats treated with baicalin (450 mg/kg), respectively. Co-administration of baicalin increased the mean AUC of phenacetin by 16%, and the mean C60 min of phenacetin by 104%[3].

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Drug Inhibition Assays.[1]
Sf9 cells were infected with high titer viral stocks (moi = 3) and cultured for 48 h. Cells were preincubated with drug for 30 min at 25°C, arachidonic acid (100 μl, final concentration 5 or 30 μM) was then added for an additional 10-min incubation at 37°C. Supernatant was assayed for COX activity by RIA for PGE2. Assays were performed multiple times in triplicate. Inhibition curves were constructed and IC50 values were determined using PRISM 3.0

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Measurement of Rat Plasma Protein Binding of Phenacetin in vitro[3]
The effect of baicalin on protein binding of phenacetin in fresh rat plasma (n = 5) was measured in vitro.The final phenacetin concentration was 7 mg/L and baicalin concentrations varied from 0 to 2000 mg·L−1 in plasma samples. The samples were incubated for 30 min at 37°C and were placed into an ultrafiltration tubes. The samples were centrifuged at 4500 rpm for 15 min. Concentration of phenacetin in the filtrate was determined by the method described above.

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For cyclooxygenase inhibition assays, Sf9 insect cells were infected with baculovirus expressing COX-1, COX-2, or COX-3 at MOI=3 and cultured for 48 hours. Cells were preincubated with the test drug for 30 minutes at 25°C. Arachidonic acid (final concentration 30 μM or 5 μM) was then added and incubated for an additional 10 minutes at 37°C. The supernatant was assayed for COX activity by radioimmunoassay (RIA) for PGE2 production. IC50 values were determined using PRISM 3.0 software. [1]

Measurement of drug concentration in plasma[2]
Chromatography analysis was performed using an Agilent 1200 HPLC system equipped with a quaternary pump, a degasser, an autosampler, a thermostatted column compartment, and an API 4,000 triple quadrupole instrument (AB/MDSSciex, Ontario, Canada).The separation was achieved on a 150 mm × 2.1 mm, 3.5 µm particle, Agilent Zorbax SB-C18 column at 30 °C. The mobile phase consisted of a mixture of 0.1% formic acid in water and acetonitrile (45:55, v: v) (Merck KGaA, Germany) at a flow rate of 0.4 mL/min. A typical injection volume was 10 µL.The quantification was performed by the peak-area method. The determination of target ions were performed in SIM mode (m/z 180 for phenacetin, m/z 271 for tolbutamide, m/z 167 for chlorzoxazone, m/z 327 for midazolam and m/z 237 for IS) and positive ion electrospray ionization interface. Drying gas flow was set to 6 L/min and temperature to 350 °C. Nebulizer pressure and capillary voltage of the system were adjusted to 20 psi and 3,500 V, respectively. The limits of quantification for phenacetin, tolbutamide, chlorzoxazone, and midazolam were 10, 20, 15 and 8 ng/mL.[2]

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Kinetic parameter of CYP1A2 and IC50 of baicalin to CYP1A2 in HLM from individuals were determined. Moreover the Ki value in pooled HLMs was estimate. The CYP1A2 activity was assessed by formation of acetaminophen from phenacetin, a probe substrate. The incubation mixture contained HLMs (0.3 mg/ml), 100 mM phosphate buffer (pH7.4), phenacetin and baicalin at different concentrations with NADPH (1 mM). The mixture was pre-incubated for 5 min at 37°C and the optimal incubation time was 30 min.[3]
For the biotransformations, eight substrate concentrations were examined over the following ranges: 6.25 to 800 µM for phenacetin. Km and Vmax values of each HLM were determined by nonlinear regression analysis. To estimate the Ki value, different concentrations of phenacetin (12.5, 25, 50,100, 200 µM) and baicalin (0, 10, 20, 40, 80 µM) were used in pooled HLMs (n = 9). The 9 individual HLMs were selected according to CYP1A2 genotype and the value of Km from the 28 individual HLMs. The mechanism of inhibition was estimated graphically from Lineweaver–Burk plots. Ki value was calculated via second plot of the slopes from Lineweaver–Burk plots versus inhibitor concentrations. Moreover, the substrate concentration was chosen close to Km and IC50 of baicalin to CYP1A2 in each HLM was determined.[3]
Termination of the enzyme reaction was by addition of ice-cold acetonitrile. The method of determining acetaminophen, the metabolite of phenacetin, was as follows. The incubation tubes were vortexed and centrifuged then 80 µl clear supernatant was injected to the HPLC system. The mobile phase consisted of methanol and 0.05 M ammonium acetate (20∶80, v/v) at a flow rate of 1 ml·min−1. The UV detection wavelength was 257 nm.[3]

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Effects of Baicalin on Phenacetin Pharmacokinetics in Rats in vivo[3]
Sprague–Dawley rats were chosen to conduct this experiment and drug dosing was done via the tail vein. The study was based on a randomized, two-period crossover design at intervals of 4 days. Eleven rats were randomly divided into two groups. Group 1 included 6 rats and group 2 included 5 rats. During the phase I, the rats in group 1 were treated with normal saline (control) and the rats in group 2 were treated with baicalin (450 mg/kg, i.v.). After that an i.v. dose (5 mg/kg) of phenacetin was given immediately. Blood samples were collected before and at 0, 5, 15, 30, 60, 90 and 120 min after administration by orbital bleeding via heparinized capillary tubes. The sample at 0 min was collected immediately after i.v. injection of phenacetin. Plasma was separated from the blood by centrifugation at 4000 rpm for 10 min and was stored at −30°C until analyzed. After a washout period of 4 days, the two groups crossed over to receive the alternative drug.

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Determination of Plasma Phenacetin and Baicalin Concentration[3]
Plasma concentration of phenacetin was determined by HPLC-UV. 1 ml acetic ether was added to 0.1 ml of plasma from each sample and vortexed for 2 min. The samples were centrifuged and the organic phase was evaporated to dryness under a stream of nitrogen. The residue was reconstituted in 100 µl of mobile phase and 50 µl was injected to the HPLC system. The mobile phase consisted of methanol and water (51∶49, v/v) at a flow rate of 1 ml·min−1. The UV detection wavelength was 247 nm.The method of determining plasma baicalin concentration had been reported previously [3].

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After complete the modeling, a cocktail solution at a dose of 5 mL/kg, which contained phenacetin (20 mg/kg), tolbutamide (5 mg/kg), chlorzoxazone (20 mg/kg) and midazolam (10 mg/kg) in CMC-Na solution, was administered orally to all rats in each group. Blood samples of each rat were collected as the following times: pre-dose (0 h) and then at 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8, 12, 24, 48 h after probe drugs administration through the tail vein and immediately separated by centrifugation at 13,000 rpm for 10 min to obtain plasma. The total volume of blood taken from each animal did not exceed 2.2 mL. A total of 100 µL plasma samples were transferred to a new tube and stored frozen at −80 °C until analyzed. Rats of smoking group and control group (n=4) were killed. Each liver sample was quickly removed and store at −80 °C[2].

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Male Sprague-Dawley rats (180-200 g) were divided into long-term smoking group (exposed to passive smoke from 6 cigarettes/day for 2 hours/day, 5 days/week for 180 days) and control group (no smoke). After the smoking period, a cocktail solution containing phenacetin (20 mg/kg), tolbutamide (5 mg/kg), chlorzoxazone (20 mg/kg), and midazolam (10 mg/kg) in CMC-Na solution was administered orally at a volume of 5 mL/kg. Blood samples were collected from the tail vein at pre-dose (0 h) and at 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8, 12, 24, and 48 hours after administration. Plasma was separated by centrifugation at 13,000 rpm for 10 minutes. [2]

Absorption, Distribution and Excretion
The oral absorption of phenacetin is significantly affected by the particle size of the formulation, resulting in correspondingly large variations in plasma concentrations of phenacetin and acetaminophen. Peak plasma concentrations of phenacetin typically occur within approximately 1 hour, while peak concentrations of the derived acetaminophen occur within 1–2 hours. Absorption is rapid after oral administration…the duration of action is approximately 4 hours. In rats given oral [acetyl-(14)C]phenacetin, up to 45% of (14)C was recovered in urine and up to 1% in feces after 16 hours. For more complete data on the absorption, distribution, and excretion of phenacetin (9 types), please visit the HSDB record page. Metabolism/Metabolites Metabolized in vivo to acetaminophen. Acetaminophen and phenacetin are primarily metabolized by hepatic microsomal enzymes. ...In a normal human body, 75% to 80% of phenacetin ingested is rapidly metabolized to acetaminophen. ...Phenacetin is converted into at least a dozen other metabolites, including hydroquinone butylamine via N-deacetylation, and further metabolism of phenacetin and hydroquinone butylamine via hydroxylation. An unknown metabolite, but an oxidizing agent, is a cause of methemoglobin formation and hemolysis of red blood cells... Phenacetin is metabolized to acetaminophen, which is excreted as a glucuronide and sulfate conjugate... ...N-hydroxyphenacetin has been identified as...a metabolite in the human body. For more complete data on the metabolism/metabolites of phenacetin (15 in total), please visit the HSDB record page. Known human metabolites of phenacetin include N-hydroxyphenacetin and acetaminophen. Metabolized in the body to acetaminophen.

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Biological half-life
The elimination half-life (t1/2)β is 37 to 74 minutes.

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Phenacetin is rapidly O-deethylated in the body to form acetaminophen. [1]
In control rats (non-smoking), the pharmacokinetic parameters of phenacetin after oral administration (20 mg/kg) were: t1/2 = 2.06 ± 0.65 h; Tmax = 0.25 ± 0.07 h; Cmax = 6,728.3 ± 52.4 μg/L; AUC0-∞ = 10,971.1 ± 238.4 μg·h/L; MRT0-∞ = 1.37 ± 0.41 h; CL/F = 1.641 ± 0.469 L/h/kg. In long-term smoking rats, significant changes were observed: t1/2 decreased to 0.75 ± 0.10 h; Cmax decreased to 4,940.0 ± 18.0 μg/L; AUC0-∞ decreased to 7,451.6 ± 123.9 μg·h/L; CL/F increased to 2.209 ± 0.494 L/h/kg (P<0.05), indicating induction of CYP1A2 activity. [2]

Toxicity Overview: Phenacetin's analgesic effect stems from its action on spinal sensory pathways. Additionally, phenacetin has a cardiodepressant effect, acting as a negative inotropic agent. It is an antipyretic, acting on the brain to lower the body's temperature regulation point. It is also used to treat rheumatoid arthritis (subacute) and intercostal neuralgia. Toxicity Data: Acute oral toxicity (LD50): 866 mg/kg [mice]. Toxin and Toxin Target Database (T3DB) 12.1.6 Interactions: Sodium 3-hydroxy-4-iodo-2-naphthoate and sodium 1-hydroxy-4-bromonaphthoate inhibit the intestinal absorption of phenacetin in rats. Simultaneous oral administration of phenacetin and one of these agents decreased phenacetin concentrations in the blood, brain, and kidneys of rats, while increasing concentrations in the liver. In rabbits, blood concentrations of phenacetin decreased with both drugs but increased with sodium 1-hydroxy-2-naphthoate, sodium tetrahydro-1-hydroxy-2-naphthoate, and sodium tetrahydro-3-hydroxy-2-naphthoate. All tested derivatives reduced the in vitro metabolism of phenacetin in rat or rabbit liver tablets. Niwa H et al.; Tohoku Pharmaceutical University Research Annual Report 18: 1 (1971) Hazardous Substances Database (HSDB) In rat liver treated with caffeine or antipyrine, the conversion of acetylphenacetin to N-acetyl-p-aminophenol was increased. The lungs and intestines also metabolize acetylphenacetin to this metabolite, and exposure to cigarette smoke enhances this metabolic pathway. After test doses of acetanilide in human subjects, plasma concentrations of acetanilide were lower in smokers than in non-smokers. Therefore, in addition to the liver, the lungs and intestines may also play important roles in the metabolism of acetanilide.

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Phenacetin is associated with methemoglobinemia, renal toxicity, and suspected renal and bladder carcinogenesis, which led to its discontinued extensive use. [1]

[1]. COX-3, a cyclooxygenase-1 variant inhibited by acetaminophen and other analgesic/antipyretic drugs: cloning, structure, and expression. Proc Natl Acad Sci U S A. 2002 Oct 15;99(21):13926-31.
[2]. Effects of long-term smoking on the activity and mRNA expression of CYP isozymes in rats. J Thorac Dis. 2015 Oct; 7(10): 1725–1731.
[3]. Inhibition of Baicalin on Metabolism of Phenacetin, a Probe of CYP1A2, in Human Liver Microsomes and in Rats. PLoS One. 2014; 9(2): e89752.
[4]. https://en.wikipedia.org/wiki/Phenacetin

According to California labor law, phenacetin may be carcinogenic. Phenacetin is an odorless, white, fine crystalline solid with a slightly bitter taste. It is used as an analgesic. Phenacetin belongs to the acetamide class of compounds, with its structure consisting of a 4-ethoxyphenyl group replacing the hydrogen atom bonded to the nitrogen atom in the acetamide molecule. It is a non-narcotic analgesic, a peripheral nervous system drug, and a cyclooxygenase 3 inhibitor. It belongs to the acetamide and aromatic ether class of compounds. Functionally, it is associated with N-phenylacetamide, 4-ethoxyaniline, and acetaminophen. Due to concerns about kidney disease (kidney damage or disease), phenacetin was withdrawn from the Canadian market in June 1973. Phenacetin is a synthetic white crystalline solid, slightly soluble in water and benzene, soluble in acetone, and very soluble in pyrimidines. In studies, it has been used as a preferred marker for in vitro detection of CYP1A2 inhibitory potential. In humans, phenacetin can cause cyanosis (blue skin due to blood hypoxia), accompanied by dizziness and respiratory depression. It is reasonably expected to be a human carcinogen. (NCI05)
Phenacetin was withdrawn from the Canadian market in June 1973 due to concerns about kidney disease (kidney damage or disease).
Phenacetin is a phenylacetamide drug that was used for analgesia, but was eventually withdrawn from the market because it caused kidney disease and methemoglobinemia. (Quoted from Smith and Reynard, Textbook of Pharmacology, 1991, p. 431)
See also: Aspirin; Butabiturate; Caffeine (note moved here).
Drug Indications
Primarily used as an analgesic.
Mechanism of Action
This study aimed to examine the selectivity of the old analgesic phenacetin and its metabolite for phenethylamine (which has high nephrotoxicity) on cyclooxygenase (COX)-1/COX-2. Acetaminophen (paracetamol) is the main metabolite of phenacetin and has low nephrotoxicity; therefore, it and indomethacin were selected as reference compounds in this study. Collagen-stimulated platelet thromboxane B2 (TxB2) production and phorbol ester (PMA)-induced neutrophil prostaglandin E2 (PGE2) synthesis were used as indicators of COX-1 and COX-2 activities, respectively. Phenacetin's ability to inhibit TxB2 and PGE2 production was even weaker than that of acetaminophen, and no significant preference for either COX enzyme was observed. Phenylacetidine effectively inhibited the synthesis of these prostaglandins at nanomolar concentrations, with a stronger inhibitory effect than indomethacin, and showed a certain preference for COX-2 inhibition. Slightly higher concentrations (micromolar levels) of phenylacetidine also reduced COX-2 expression in neutrophils. We believe that the potent inhibition of PGE2 synthesis by phenacetin, along with the decrease in COX-2 expression, may explain the renal papillary necrosis observed in phenacetin-treated kidneys. Analgesic nephropathy is a unique drug-induced kidney disease characterized by renal papillary necrosis and chronic interstitial nephritis, resulting from overdose of compound antipyretic analgesics. Clinical manifestations primarily include renal papillary necrosis, renal colic, and obstructive urinary tract disease; a small percentage of patients develop chronic renal failure. Significant regional variations in clinical presentation exist, possibly related to different combinations of analgesics. The pathogenesis of this disease is partly related to the kidney's ability to concentrate drugs in the renal papillae. The following sequence of events provides a plausible explanation for the progression of this disease. If phenacetin and aspirin are ingested simultaneously, the following steps occur: Phenacetin is first-pass metabolized in the intestine and liver to acetaminophen. Acetaminophen is then absorbed by the kidneys and excreted. During excretion, due to its physiological antidiuretic effect, acetaminophen concentrates in the renal papilla, reaching concentrations up to five times higher than those in other tissue cells. Acetaminophen is oxidized and metabolized by prostaglandin H synthase to an active quinone imine, which binds to glutathione. If only acetaminophen is ingested, the glutathione produced in the renal papilla is sufficient to detoxify this active intermediate. If acetaminophen and aspirin are ingested simultaneously, aspirin is converted to salicylic acid, which becomes highly concentrated in the renal cortex and renal papilla. Salicylic acid is a potent depleter of glutathione. The mechanism is not fully understood; however, the effect of the pentose pathway on NADPH production may be one explanation. When intracellular glutathione is depleted, the active metabolites of acetaminophen produce lipid peroxides and lead to arylization of tissue proteins, ultimately resulting in papillary necrosis. The analgesic mechanism is not fully understood. Acetaminophen likely exerts its effects primarily by inhibiting prostaglandin synthesis in the central nervous system (CNS), and secondarily by blocking the generation of pain impulses through peripheral effects. Peripheral effects may also be due to the inhibition of the synthesis or function of other pain receptors sensitive to mechanical or chemical stimuli. Acetaminophen may also produce an antipyretic effect by acting on the hypothalamic thermoregulatory center, causing peripheral vasodilation, thereby increasing skin blood flow, promoting sweating and heat dissipation. Its main mechanism of action may involve the inhibition of prostaglandin synthesis in the hypothalamus.

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Phenacetin is a once popular analgesic/antipyretic drug that is no longer extensively used due to its toxicity. Its active metabolite is acetaminophen. In pharmacological studies, phenacetin selectively inhibits COX-3 over COX-1 and COX-2. It is also widely used as a probe substrate for CYP1A2 enzyme activity in drug-drug interaction and pharmacokinetic studies. [1][2]

C10H13NO2

179.22

179.094

C, 67.02; H, 7.31; N, 7.82; O, 17.85

62-44-2

Phenacetin;62-44-2

4754

White to off-white solid powder

1.0±0.1 g/cm3

323.6±44.0 °C at 760 mmHg

133-136 °C(lit.)

149.5±28.4 °C

0.0±0.7 mmHg at 25°C

1.506

2.01

1

2

3

13

162

0

CPJSUEIXXCENMM-UHFFFAOYSA-N

InChI=1S/C10H13NO2/c1-3-13-10-6-4-9(5-7-10)11-8(2)12/h4-7H,3H2,1-2H3,(H,11,12)

N-(4-Ethoxyphenyl)acetamide

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.)