In rats that have had their ovariectomies (OVX) performed, raloxifene (4 mg/kg; intragastric injection; once daily for 13 weeks) dramatically reduces bone loss [1].

Animal/Disease Models: Female, 12 weeks old, Wistar rats (OVX rats) [1]
Doses: 4 mg/kg
Route of Administration: gavage; one time/day for 13 weeks
Experimental Results: E2 levels increased Dramatically in OVX rats High, BGP levels are Dramatically diminished.

Absorption, Distribution and Excretion
Raloxifene is well absorbed from the gastrointestinal tract, with approximately 60% of the drug absorbed after oral administration. Due to its extensive first-pass hepatic metabolism (involving glucuronide conjugation), the absolute oral bioavailability of raloxifene is approximately 2%. In healthy postmenopausal women, the mean peak plasma concentration (Cmax) after a single or multiple oral dose of raloxifene was 0.50 and 1.36 ng/mL, respectively, with AUC values of 27.2 and 24.2 ng·hr/mL, respectively. The time to reach Cmax after a single or multiple oral dose was 27.7 hours and 32.5 hours, respectively. Although clinically insignificant, oral administration of raloxifene with a high-fat meal is believed to improve systemic bioavailability, increasing peak plasma concentration (Cmax) and AUC by 28% and 16%, respectively. Raloxifene is primarily excreted in the feces, with less than 0.2% of the dose excreted unchanged in the urine and less than 6% excreted as glucuronide conjugates. Concomitant use with the bile acid sequestrant cholestyramine reduces the enterohepatic circulation of raloxifene by 60%. In postmenopausal women, the volume of distribution after a single oral dose of 30 to 150 mg raloxifene is approximately 2348 L/kg. After multiple oral doses, its clearance increases to 2853 L/kg. Raloxifene is widely distributed in tissues. It is unknown whether raloxifene is excreted into human milk. After intravenous administration, the clearance rate of raloxifene is similar to that of hepatic blood flow. The apparent oral clearance has been reported to be 44.1 L/kg·hr. With prolonged administration, clearance can decrease to 40 to 60 L/kg·hr. In healthy postmenopausal women, the mean clearance after multiple oral doses is 47.4 L/kg·hr. Apparent clearance can be reduced by 56% in patients with hepatic impairment. It is unknown whether raloxifene can cross the human placenta. Its molecular weight (free base approximately 474) and long elimination half-life suggest that the drug may cross the placenta and enter the embryo. However, high plasma protein binding may limit drug exposure. Raloxifene undergoes extensive first-pass glucuronidation and enterohepatic circulation, with peak plasma concentrations of its glucuronide conjugates reached faster than the parent drug. Following a single oral dose of 120 or 150 mg raloxifene hydrochloride, peak plasma concentrations of raloxifene and its glucuronide conjugates were reached at 6 hours and 1 hour, respectively. The plasma concentrations of raloxifene glucuronide conjugates were higher than those of the parent drug, and the time to reach maximum concentrations of the drug and its glucuronide metabolites depended on the extent and rate of systemic interconversion and enterohepatic circulation. After oral administration of radiolabeled raloxifene, the proportion of the parent drug in the total circulating radiolabeled material in plasma was less than 1%. Following a single oral dose of 30–150 mg raloxifene hydrochloride, the apparent volume of distribution was 2348 L/kg, indicating extensive tissue distribution. According to reports, within the daily dose range of 30-150 mg, the volume of distribution is dose-independent. Raloxifene is primarily excreted in feces as unabsorbed drug and also in bile as a glucuronide conjugate, which is subsequently metabolized to the parent drug by bacteria in the gastrointestinal tract. After oral administration, less than 6% and 0.2% of the raloxifene dose are excreted in urine as glucuronide conjugates or unchanged drug, respectively. For more complete data on absorption, distribution, and excretion of raloxifene (11 items in total), please visit the HSDB records page. Metabolism/Metabolites Raloxifene is reportedly metabolized in the intestine and liver, but its metabolic pathway does not involve cytochrome P450. It is extensively metabolized, with less than 1% of the total dose remaining in its original form. Raloxifene is primarily metabolized via first-pass metabolism to glucuronide conjugates, including raloxifene-4'-glucuronide (raloxifene-4'-β-glucuronide), raloxifene-6-glucuronide (raloxifene-6-β-glucuronide), and raloxifene-6,4'-disglucuronide. No other metabolites have been detected in human plasma. The log-linear portions of the plasma concentration curves for raloxifene and its glucuronides are generally parallel. This is consistent with the interconversions between raloxifene and its glucuronide metabolites. Following oral administration of 14C-labeled raloxifene, the biotransformation and distribution of raloxifene in humans have been determined. Raloxifene undergoes extensive first-pass metabolism to glucuronide conjugates: raloxifene-4'-glucuronide, raloxifene-6-glucuronide, and raloxifene-6,4'-disglucuronide. No other metabolites were detected, strongly suggesting that raloxifene is not metabolized via the cytochrome P450 pathway. Free raloxifene in plasma accounts for less than 1% of the total radiolabeled content. The logarithmic linear portions at the ends of the plasma concentration curves for raloxifene and its glucuronide are generally parallel. This is consistent with the interconversion between raloxifene and its glucuronide metabolites. The metabolism of raloxifene does not appear to be mediated by cytochrome P-450 enzymes, as no other metabolites have been found besides the glucuronide conjugate. Known metabolites of raloxifene include [6,7-dihydroxy-2-(4-hydroxyphenyl)benzo[b]thiophen-3-yl][4-(2-piperidinylethoxy)phenyl] methyl ketone, [2-(3,4-dihydroxyphenyl)-6-hydroxy-1-benzothiophen-3-yl]-[4-(2-piperidinyl-1-ylethoxy)phenyl] methyl ketone, and raloxifene 6-O-glucuronide.

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Biological Half-Life
The mean plasma elimination half-life of raloxifene is 27 to 32 hours. The prolonged half-life of raloxifene is attributed to its reversible systemic metabolism and significant enterohepatic circulation.
The mean steady-state plasma elimination half-life of raloxifene is 32.5 hours (range: 15.8–86.6 hours).
Raloxifene and its glucuronide conjugates can be interconverted through reversible systemic metabolism and enterohepatic circulation, thus prolonging the plasma elimination half-life after oral administration to 27.7 hours.

Toxicity Summary
Identification and Uses: Raloxifene is used to treat and prevent osteoporosis in postmenopausal women and to reduce the risk of invasive breast cancer in postmenopausal women with osteoporosis. Human Studies: No deaths due to raloxifene overdose have been reported. Post-marketing reports indicate that approximately half of adults taking ≥180 mg of raloxifene hydrochloride reported adverse reactions, including leg cramps and dizziness. Raloxifene treatment is associated with an increased risk of venous thromboembolic events, such as deep vein thrombosis and pulmonary embolism. An increased risk of stroke death was found in a trial in postmenopausal women with a history of coronary artery disease or an increased risk of major coronary events. A small number of cases of osteonecrosis of the jaw have been associated with raloxifene. Two 18-month-old children who ingested 180 mg of raloxifene hydrochloride reported symptoms including ataxia, dizziness, vomiting, rash, diarrhea, tremor, and flushing, as well as elevated alkaline phosphatase. Raloxifene is fetal toxic to pregnant women. As raloxifene is an estrogen agonist-antagonist, it is expected to affect reproductive function. Animal studies: No deaths were observed in rats and mice after a single oral dose of 5000 mg/kg raloxifene hydrochloride, and no deaths were observed in monkeys after a single oral dose of 1000 mg/kg raloxifene hydrochloride. In a 21-month mouse carcinogenicity study, female mice showed an increased incidence of ovarian tumors after daily oral administration of 9–242 mg/kg raloxifene hydrochloride, while male mice showed an increased incidence of testicular interstitial cell tumors, prostate adenomas, and adenocarcinomas after daily oral administration of 41 or 210 mg/kg raloxifene hydrochloride. In rat studies, administration of raloxifene hydrochloride at doses of 0.1–10 mg/kg during pregnancy and lactation delayed and disrupted parturition, reduced neonatal survival, altered pupal physical development, leading to sex- and age-specific slowed growth and development, changes in pituitary hormone levels, and reduced lymphoid tissue volume. Rats administered 10 mg/kg raloxifene hydrochloride experienced birth disturbances, leading to morbidity and/or death in both mothers and pups. While no ovarian or vaginal lesions were observed in adult offspring (4 months of age), uterine hypoplasia and decreased fertility were noted. In rabbit reproductive studies with raloxifene hydrochloride, doses of 0.1 mg/kg or higher resulted in abortion with a low incidence of fetal cardiac malformations such as ventricular septal defects. Fetal hydrocephalus was observed in rabbits treated with raloxifene at doses of 10 mg/kg or higher (at least four times the recommended human dose per mg/m²). In female rats, raloxifene at doses ranging from 0.1 to 10 mg/kg/day disrupted the estrous cycle and inhibited ovulation. These effects of raloxifene were reversible. No pregnancy occurred in male or female rats when administered ≥5 mg/kg raloxifene daily before and during mating. In reproductive studies in rats, fetal growth retardation and developmental abnormalities (e.g., wavy ribs, cavitary kidneys) were observed with doses of raloxifene hydrochloride at 1 mg/kg or higher. Raloxifene has not shown mutagenicity in in vitro and in vivo studies, including the Ames microbial assay with/without metabolic activation, the rat hepatocyte unplanned DNA synthesis assay, the mammalian cell mutation mouse lymphoma assay, the Chinese hamster ovary cell chromosomal aberration assay, the Chinese hamster sister chromatid exchange assay, and the mouse micronucleus assay. Protein Binding: Approximately 95% of raloxifene and its glucuronide metabolites are bound to plasma proteins. Despite the relatively high protein binding rate of raloxifene, in vitro studies have shown no significant interaction between raloxifene and its metabolites and highly protein-bound drugs. The FDA drug label still recommends caution when using raloxifene in combination with other highly protein-bound drugs. Drug Interactions: The manufacturer notes that due to a lack of experience from prospective clinical trials, concomitant use of systemic estrogens with raloxifene is currently not recommended.
Concomitant use of raloxifene and ampicillin results in a 28% decrease in peak plasma concentration of raloxifene and a 14% decrease in absorption. These changes in raloxifene absorption are consistent with reduced enterohepatic circulation due to decreased gut bacteria. Since systemic exposure and elimination of raloxifene are unaffected, raloxifene can be used concurrently with ampicillin. In female patients with osteoporosis receiving raloxifene treatment, concomitant use of amoxicillin does not affect raloxifene plasma concentrations. Raloxifene can be taken concurrently with amoxicillin.
Although the long-term effects of raloxifene and warfarin have not been studied, and the drug has been reported not to affect the protein binding rate of anticoagulants, a single dose of raloxifene and warfarin concurrently can shorten prothrombin time by 10% compared to warfarin alone. In female patients with osteoporosis receiving raloxifene treatment, concomitant use of warfarin does not affect raloxifene plasma concentrations. If these medications are used concurrently, patients and prothrombin time should be closely monitored, and the anticoagulant dosage adjusted accordingly.
Concomitant use of cholestyramine and raloxifene can reduce raloxifene absorption and enterohepatic circulation by 60%. The manufacturer states that raloxifene should not be used concurrently with cholestyramine. Although no specific studies have been conducted, other anion exchange resins are expected to also reduce raloxifene absorption and enterohepatic circulation.
Raloxifene binds to plasma proteins at a rate exceeding 95%. The manufacturer states that concomitant use of raloxifene with other drugs with high protein binding rates is not expected to affect raloxifene plasma concentrations. In female patients with osteoporosis receiving raloxifene treatment, concomitant use of other drugs with high protein binding rates (such as gemfibrozil) does not affect raloxifene plasma concentrations. Raloxifene has been reported not to affect the protein binding rates of phenytoin sodium, tamoxifen, or warfarin in vitro. The manufacturer notes that caution should be exercised when using raloxifene concurrently with other drugs that have high protein binding rates (such as diazepam, diazoxide, or lidocaine).

[1]. Clinical effects of raloxifene hydrochloride in women. Ann Intern Med. 1999;130(5):431-439.

[2]. Effect of caffeine on ovariectomy-induced osteoporosis in rats. Biomed Pharmacother. 2019;112:108650.

Therapeutic Uses
Estrogen antagonists; selective estrogen receptor modulators; bone mineral density protectants. ClinicalTrials.gov is a registry and results database that indexes human clinical studies funded by public and private institutions worldwide. The website is maintained by the National Library of Medicine (NLM) and the National Institutes of Health (NIH). Each record on ClinicalTrials.gov includes a summary of the study protocol, including: the disease or condition; the intervention (e.g., the medical product, behavior, or procedure under investigation); the title, description, and design of the study; participation requirements (eligibility criteria); the location of the study; contact information for the study location; and links to relevant information from other health websites, such as the NLM's MedlinePlus (for patient health information) and PubMed (for citations and abstracts of academic articles in the medical field). Raloxifene is indexed in the database. Evista is indicated for the treatment and prevention of osteoporosis in postmenopausal women. /Included in the US product label/
Evista is indicated for reducing the risk of invasive breast cancer in postmenopausal women with osteoporosis. /Included in the US product label/
For more complete therapeutic use data for raloxifene (one of 14), please visit the HSDB record page.

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Drug Warning
Tamoxifen use is associated with an increased incidence of cataracts and cataract surgery.In the STAR study, the incidence of cataracts (RR 0.79; 95% confidence interval: 0.68–0.92) and the rate of cataract surgery (RR 0.82; 95% confidence interval: 0.68–0.99) were both lower in patients treated with raloxifene than in patients treated with tamoxifen.
In a study of postmenopausal women with coronary artery disease (CHD) or risk factors for CHD (the RUTH study), raloxifene use did not affect the risk of coronary events. In the STAR study, the incidence of ischemic heart disease (i.e., myocardial infarction, severe angina, acute ischemic syndrome) was similar in patients treated with raloxifene to that in patients treated with tamoxifen. During the 5-year study period, at almost every assessment, the proportion of sexually active women treated with raloxifene was lower than that of women treated with tamoxifen. Among sexually active women, those taking raloxifene reported difficulties with sexual arousal, sexual interest, and sexual pleasure. In clinical studies, up to 2.3% of patients treated with raloxifene experienced syncope or varicose veins. In clinical trials, up to 14.1% of women treated with raloxifene experienced peripheral edema. For more complete data on drug warnings for raloxifene (25 total), please visit the HSDB records page.

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Pharmacodynamics
Raloxifene belongs to the class of selective estrogen receptor modulators (SERMs). It has estrogen-like effects on bone and lipid metabolism, while also having anti-estrogenic effects on the endometrium and breast tissue. In bone tissue, raloxifene stimulates osteoblasts to deposit bone tissue and inhibits osteoclasts to resorb bone tissue, thereby increasing bone mineral density. Raloxifene has estrogen-like effects on bone, reducing bone resorption and increasing bone mineral density in postmenopausal women, thus slowing bone loss. In three randomized, placebo-controlled trials conducted in Europe, postmenopausal women taking different doses of raloxifene daily (30 to 150 mg) had significantly higher bone mineral density in the lumbar spine, hip, femoral neck, and throughout the body than the placebo group. In the MORE and RUTH trials, the incidence of vertebral fractures in postmenopausal women taking raloxifene was lower than in the placebo group. An eight-week study evaluated the short-term efficacy of raloxifene in healthy postmenopausal women, showing a decrease in bone turnover markers, such as serum alkaline phosphatase levels, serum osteocalcin levels, and urinary calcium excretion. In vitro experiments showed that raloxifene inhibited estrogen-dependent proliferation of human breast cancer cells; in vivo experiments showed that raloxifene inhibited the development of induced mammary tumors in rats. In adult female rats, raloxifene induced greater mammary atrophy than tamoxifen. The MORE trial was a multicenter, randomized, double-blind clinical trial designed to investigate the long-term efficacy of raloxifene treatment in postmenopausal women in Europe and the United States after 40 months. Furthermore, the CORE and RUTH trials also confirmed that raloxifene reduces the incidence of invasive breast cancer. Results showed that, compared to placebo, raloxifene reduced the risk of invasive breast cancer by 76% in postmenopausal women with osteoporosis. The risk of estrogen receptor-positive breast cancer was reduced by 90%, but the risk of endometrial cancer was not increased. Unlike hormone replacement therapy, raloxifene does not promote or stimulate the proliferation of endometrial tissue. Both animal and human studies have shown no significant changes in the histological morphology of the endometrium. Raloxifene has estrogen-like effects on lipid metabolism. A European trial evaluating lipid profiles after 24 months of raloxifene treatment showed significant reductions in serum total cholesterol and low-density lipoprotein cholesterol (LDL-C) concentrations during the 24-month treatment period. Raloxifene does not cause changes in serum high-density lipoprotein cholesterol (HDL-C) or triglyceride levels. Because HDL-C levels are considered a strong negative predictor of cardiovascular disease in women, the cardioprotective effect of raloxifene has been questioned. Due to limited long-term trial data, it is not yet possible to determine whether the slight lipid changes produced by raloxifene are related to its weaker cardioprotective effect (compared to hormone replacement therapy).

C28H27NO4S

473.59

473.166

84449-90-1

Raloxifene hydrochloride;82640-04-8;Raloxifene-d4;1185076-44-1;Raloxifene-d4 hydrochloride;1188263-47-9;Raloxifene-d10;Raloxifene-d10-1;2512224-37-0

5035

Light yellow to yellow solid powder

1.3±0.1 g/cm3

728.2±60.0 °C at 760 mmHg

250-253°C

394.2±32.9 °C

0.0±2.5 mmHg at 25°C

1.666

6.8

2

6

7

34

655

0

GZUITABIAKMVPG-UHFFFAOYSA-N

InChI=1S/C28H27NO4S/c30-21-8-4-20(5-9-21)28-26(24-13-10-22(31)18-25(24)34-28)27(32)19-6-11-23(12-7-19)33-17-16-29-14-2-1-3-15-29/h4-13,18,30-31H,1-3,14-17H2

[6-hydroxy-2-(4-hydroxyphenyl)-1-benzothiophen-3-yl]-[4-(2-piperidin-1-ylethoxy)phenyl]methanone

Raloxifenum; Pharoxifene; Raloxifene

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 : ~100 mg/mL (~211.16 mM)

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.)