Chemical formula: C₂₁H₂₈O₂ Molecular mass: 312.453 g/mol PubChem compound: 444008
Tibolone interacts in the following cases:
Herbal preparations containing St.John’s wort (Hypericum Perforatum) may induce the metabolism of oestrogens and progestogens via CYP3A4. Clinically, an increased metabolism of oestrogens and progestogens may lead to decreased effect and changes in the uterine bleeding profile.
CYP3A4 inducing compounds such as barbiturates, carbamazepine, hydantoins and rifampicin may enhance the metabolism of tibolone and thus affect its therapeutic effect.
There is limited information regarding pharmacokinetic interactions with tibolone. An in vivo study showed that simultaneous treatment of tibolone affects pharmacokinetics of the cytochrome P450 3A4 substrate midazolam to a moderate extent. Based on this, drug interactions with other CYP3A4 substrates might be expected.
Since Tibolone may increase blood fibrinolytic activity, it may enhance the effect of anticoagulants. This effect has been demonstrated with warfarin. Caution should therefore be exercised during the simultaneous use of Tibolone and anticoagulants, especially when starting or stopping concurrent Tibolone treatment. If necessary, the dose of warfarin should be adjusted.
In animal studies, tibolone had anti-fertility activities by virtue of its hormonal properties.
Treatment with Tibolone results in a very minor decrease of thyroid binding globulin (TBG) and total T4. Levels of total T3 are unaltered. Tibolone decreases the level of sexhormone-binding globulin (SHBG), whereas the levels of corticoid binding globulin (CBG) and circulating cortisol are unaffected.
Women with pre-existing hypertriglyceridaemia should be followed closely during oestrogen replacement or HRT, since rare cases of large increases of plasma triglycerides leading to pancreatitis have been reported with oestrogen therapy in this condition.
Ovarian cancer is much rarer than breast cancer.
Epidemiological evidence from a large meta-analysis suggests a slightly increased risk in women taking oestrogen-only or combined oestrogen-progestagen HRT, which becomes apparent within 5 years of use and diminishes over time after stopping. Some other studies, including the Women’s Health Initiative (WHI) trial, suggest that the use of combined HRTs may be associated with a similar, or slightly smaller risk.
In the Million Women Study it was shown that the relative risk for ovarian cancer with use of tibolone was similar to the risk associated with use of other types of HRT.
Oestrogens may cause fluid retention, and therefore patients with cardiac or renal dysfunction should be carefully observed.
If any of the following conditions are present, have occurred previously, and/or have been aggravated during pregnancy or previous hormone treatment, the patient should be closely supervised. It should be taken into account that these conditions may recur or be aggravated during treatment with Tibolone, in particular:
Therapy should be discontinued in case a contra-indication is discovered and in the following situations:
Tibolone is contraindicated during pregnancy. If pregnancy occurs during medication with tibolone, treatment should be withdrawn immediately. For tibolone no clinical data on exposed pregnancies are available. Studies in animals have shown reproductive toxicity. The potential risk for humans is unknown.
Tibolone is contraindicated during lactation.
In animal studies, tibolone had anti-fertility activities by virtue of its hormonal properties.
Tibolone is not known to have any effects on alertness and concentration.
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