- Tibolone exerts biological effects by binding to sex hormone receptors, including estrogen receptors (ER) and progesterone receptors (PR)
- Tibolone modulates sexual behavior-related pathways by acting on central nervous system (CNS) sex hormone receptors (primarily estrogen receptors)

- In a preclinical in vivo model of implant osseointegration (using ovariectomized [OVX] female Sprague-Dawley [SD] rats, which mimic postmenopausal osteoporosis): Oral administration of Tibolone at a dose of 1 mg/kg/day for 8 weeks (4 weeks before and 4 weeks after titanium implant placement into the proximal tibia) significantly enhanced osseointegration. Micro-CT analysis showed that the bone-implant contact (BIC) rate in the Tibolone group was 51.2 ± 6.3%, which was significantly higher than that in the OVX control group (29.5 ± 5.4%, p < 0.05). Additionally, the bone volume fraction (BV/TV) around the implant in the Tibolone group (0.42 ± 0.05) was 46.4% higher than that in the control group (0.28 ± 0.04, p < 0.05). Histological examination further confirmed increased new bone formation around the implant in the Tibolone -treated group, with no abnormal bone tissue morphology[1]
- In a study of lordosis behavior in female SD rats: Ovariectomized (OVX) rats were subcutaneously injected with Tibolone at a dose of 10 μg/rat once daily for 7 consecutive days. Behavioral tests (conducted by exposing rats to sexually active male rats for 10 minutes) showed that Tibolone significantly induced lordosis behavior: the lordosis score (scored on a 0–3 scale, where 3 = maximal lordosis) in the Tibolone group was 2.9 ± 0.2, which was significantly higher than that in the OVX control group (0.3 ± 0.1, p < 0.01). The lordosis frequency (percentage of male mounts that elicited lordosis) in the Tibolone group was 85.6 ± 7.2%, compared to 12.3 ± 4.5% in the control group (p < 0.01). Notably, no concurrent or sequential inhibition of lordosis behavior was observed in the Tibolone -treated group during the 14-day observation period after drug withdrawal[2]

- Protocol for implant osseointegration study: 48 female SD rats (8 weeks old, 220–250 g) were randomly divided into 4 groups (n = 12 per group): Sham-operated group (Sham), OVX control group, Tibolone -treated group (TIB), and Tibolone + alendronate + simvastatin combination group. Rats in the OVX, TIB, and combination groups underwent bilateral ovariectomy to induce postmenopausal osteoporosis; the Sham group underwent sham surgery (ovaries were exposed but not removed). Two weeks after surgery, the TIB group began receiving Tibolone (1 mg/kg/day) dissolved in 0.5% carboxymethyl cellulose (CMC) via oral gavage, once daily. Four weeks after the start of drug administration, all rats received a titanium implant (diameter 1.5 mm, length 5 mm) implanted into the proximal metaphysis of the right tibia under general anesthesia. Drug administration continued for another 4 weeks after implant placement. At the end of the 8-week treatment period, rats were euthanized; the right tibia with the implant was harvested for Micro-CT scanning, histological sectioning, and bone parameter analysis (BIC, BV/TV)[1]
- Protocol for lordosis behavior study: 30 female SD rats (10 weeks old, 230–260 g) were ovariectomized to eliminate endogenous sex hormone effects. Two weeks after OVX, rats were randomly divided into 2 groups (n = 15 per group): Tibolone -treated group and vehicle control group. The Tibolone group received subcutaneous injections of Tibolone (10 μg/rat) dissolved in sesame oil, once daily for 7 days. The control group received equal volumes of sesame oil. On the 7th day of drug administration, lordosis behavior was tested: each rat was placed in a transparent observation cage (40 × 30 × 25 cm) with a sexually experienced male rat (screened for consistent mounting behavior). The observer (blinded to group allocation) recorded the lordosis score (0 = no lordosis, 1 = partial lordosis, 2 = moderate lordosis, 3 = full lordosis) and lordosis frequency (number of lordosis responses divided by total male mounts × 100%) over a 10-minute period. Behavioral tests were repeated on days 1, 7, and 14 after drug withdrawal to assess sequential effects[2]

Absorption, Distribution and Excretion
Tibolone is rapidly and extensively absorbed after oral administration. The parent drug is extensively metabolized, with over 80% of the radioactive dose excreted as metabolites, indicating extremely low plasma concentrations. Plasma concentrations of metabolites appear within 30 minutes and peak within 1–1.5 hours. Plasma concentrations of the hydroxyl metabolite are higher than the Δ4-isomer. Food does not appear to affect the absorption of this drug. It is primarily excreted in urine and feces as a sulfate metabolite. Approximately 40% of the drug is excreted in urine as a metabolite. The main route of excretion for tibolone is feces: approximately 60% of the drug is excreted in feces as a metabolite. Tibolone excretion is independent of renal function. Metabolism/Metabolites Tibolone is primarily metabolized in the liver. The cytochrome P450 isoenzyme system is involved in the minor hydroxylation of tibolone. Tibolone is rapidly converted into three major metabolites: 3α- and 3β-hydroxytibolone, which have estrogenic effects, and the Δ(4)-isomer, which has progestogenic and androgenic effects. The 3-hydroxy metabolite exists primarily in the bloodstream as its inactive sulfate form.

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Biological half-life
The elimination half-life is approximately 45 hours.

Hepatotoxicity
In large prospective studies, tibolone was associated with a lower incidence of transient elevations in serum transaminase levels. 0.9% of patients in the tibolone group had transaminase levels exceeding three times the upper limit of normal, compared to 0.2% in the placebo group. However, no clinically significant cases of acute liver injury were reported. In Europe, where tibolone is used clinically, there have been sporadic reports of clinically significant liver injury, accompanied by hepatocellular serum enzyme elevations and jaundice, occurring 6 to 12 months after the start of treatment. All reported cases were self-limiting, resolving within 2 to 6 months after discontinuation of the drug. No signs of immune hypersensitivity or autoantibodies were observed. Probability Score: C (Possibly the cause of clinically significant liver injury). Protein Binding Tibolone binds to plasma proteins in 96% of cases, most likely albumin.

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- During the 8-week treatment period, rats in the tibolone group did not show significant changes in body weight (weekly weight gain was comparable to the control group), no abnormal clinical symptoms (e.g., lethargy, diarrhea, hair loss) were observed, and there were no significant differences in serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen (BUN), or creatinine levels compared to the sham-operated group and the ovariectomized control group, indicating that tibolone did not cause acute hepatotoxicity at the test dose [1] - No obvious toxic reactions (e.g., weight loss, abnormal activity, or organ damage) were observed in rats treated with tibolone (10 μg/rat, subcutaneous injection) for 7 days. Serum biochemical tests (ALT, AST, BUN) performed at the end of the study showed no significant differences between the tibolone group and the control group, indicating that tibolone had no acute toxicity under these experimental conditions. No drug interaction or plasma protein binding data were reported [2]

[1]. Tibolone, alendronate, and simvastatin enhance implant osseointegration in a preclinical in vivo model. Clin Oral Implants Res. 2020 Jul;31(7):655-668.
[2]. Tibolone induces lordosis behavior, but not concurrent or sequential inhibition, in Sprague Dawley rats. Neurosci Lett. 2021 Apr 24;755:135916.

Pharmacodynamics
Tibolone can prevent bone loss and treat postmenopausal symptoms without stimulating endometrial tissue, thus avoiding malignant tumors. Typically, medications for treating postmenopausal symptoms (such as estrogen) can cause endometrial proliferation, increasing the risk of endometrial cancer. Tibolone's effects on bone, brain, and vaginal tissue can be attributed to its estrogenic activity. Notably, this activity is not expressed in the endometrium. Tibolone's effects on the breast differ from the combination of estrogen and progesterone. Therefore, tibolone can be considered a selective estrogen activity modulator. Tibolone has been proven effective in treating menopausal symptoms. A 16-week trial involving 1189 women investigated the effects of once-daily 2.5 mg tibolone on menopausal symptoms. Women receiving tibolone treatment showed improvement from baseline in typical menopausal symptoms, including hot flashes, night sweats, insomnia, and anxiety.

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- Tibolone is a synthetic steroid with mixed estrogenic, progesterone and weak androgenic activity. Its ability to promote peri-implant bone formation in terms of implant osseointegration may be achieved by promoting osteoblast proliferation and differentiation, inhibiting osteoclast activity, and regulating bone metabolism-related cytokines (e.g., increasing osteoprotegerin [OPG] expression and decreasing nuclear factor κB receptor activator ligand [RANKL] expression), which is particularly important for improving implant stability in postmenopausal women with osteoporosis [1].
- Rigidity is a sexual response in female rodents regulated by central sex hormone signals. In ovariectomized (OVX) rats, tibolone induced ridge curvature, suggesting that it can replace endogenous estrogen in activating central nervous system pathways involved in sexual behavior (e.g., the hypothalamus-pituitary-gonadal axis). No concurrent or sequential inhibition was observed, suggesting that tibolone does not have a long-term inhibitory effect on sexual behavior after short-term administration, which may be of great significance for its clinical application in the treatment of estrogen deficiency-related dysfunction [2].

C21H28O2

312.44582

312.208

C, 80.73; H, 9.03; O, 10.24

5630-53-5

444008

White to off-white solid powder

1.1±0.1 g/cm3

447.4±45.0 °C at 760 mmHg

169 °C

190.6±21.3 °C

0.0±2.5 mmHg at 25°C

1.570

4.03

1

2

1

23

636

6

C#C[C@@]1(CC[C@H]2[C@@H]3[C@H](C)CC4=C(CCC(=O)C4)[C@H]3CC[C@@]21C)O

WZDGZWOAQTVYBX-JNHCMHTRSA-N

InChI=1S/C21H28O2/c1-4-21(23)10-8-18-19-13(2)11-14-12-15(22)5-6-16(14)17(19)7-9-20(18,21)3/h1,13,17-19,23H,5-12H2,2-3H3/t13-,17-,18+,19-,20+,21-/m1/s1

19-Norpregn-5(10)-en-20-yn-3-one, 17-hydroxy-7-methyl-, (7alpha,17alpha)-

Livial; Tinox; tibolone; 5630-53-5; Liviella; Livial; Org OD 14; Tibolona; Xyvion; Tibolonum; Tibofem Xyvion Tibolonum.

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)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

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.)