1. Clinical Overview
Tibolone is a synthetic steroid with tissue-specific estrogenic, progestogenic, and weak androgenic properties. It is used primarily for the management of menopausal symptoms and the prevention of postmenopausal osteoporosis. Unlike conventional hormone replacement therapy (HRT), it does not stimulate the endometrium, eliminating the need for a progestogen in women with an intact uterus.
| Onset | Duration | Bioavailability |
|---|---|---|
| Relief of vasomotor symptoms (hot flushes) typically begins within 2-4 weeks of continuous therapy. Full therapeutic effect for bone mineral density may take 6-12 months. | Approximately 24 hours, supporting once-daily dosing. | Rapid and nearly complete (approximately 100%) following oral administration. |
2. Mechanism of Action
Tibolone itself is inactive. After oral administration, it is converted into three active metabolites that exert tissue-specific effects. In bone, brain, and vagina, the 3α-OH and 3β-OH metabolites exert estrogenic effects, relieving symptoms and preventing bone loss. In the endometrium, the Δ4-isomer exerts a progestogenic effect, preventing estrogenic stimulation and hyperplasia. The Δ4-isomer also contributes to androgenic effects, which may improve libido and sense of well-being.
3. Indications & Uses
- Treatment of vasomotor symptoms (hot flushes and night sweats) associated with menopause
- Prevention of postmenopausal osteoporosis in women at high risk of future fractures
4. Dosage & Administration
Adult Dosage: 2.5 mg orally once daily. Treatment should be initiated at least 12 months after the last natural menstrual period or immediately after surgical menopause.
Administration: Tablet should be swallowed whole with water, preferably at the same time each day, with or without food. Treatment is continuous (no break). If a dose is missed, it should be taken as soon as remembered unless it is almost time for the next dose. Do not double the dose.
5. Side Effects
Common side effects may include:
- Weight gain
- Abdominal pain
- Headache
- Dizziness
- Vaginal bleeding/spotting (especially in first few months)
- Breast pain/discomfort
- Increased facial hair growth (hirsutism)
- Acne
- Seborrhea
- Edema
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Enzyme Inducers (Carbamazepine, Phenytoin, Rifampicin, St. John's Wort) | Markedly increase metabolism of Tibolone, reducing its therapeutic efficacy. May lead to breakthrough bleeding and loss of bone protection. | Major |
| Warfarin and other Coumarin Anticoagulants | Tibolone may potentiate the anticoagulant effect, increasing the risk of bleeding. Close monitoring of INR is required. | Moderate |
| Insulin and Oral Hypoglycemics | Tibolone may decrease glucose tolerance, potentially requiring adjustment of antidiabetic therapy. | Moderate |
| Corticosteroids | Potential additive effect on bone mineral density. Increased risk of edema. | Moderate |
7. Patient Counselling
- DO take the tablet at the same time every day for best results.
- DO continue regular weight-bearing exercise and ensure adequate calcium and vitamin D intake for bone health.
- DO attend all scheduled follow-up and screening appointments (mammography, pelvic exam).
- DO report any unusual vaginal bleeding, breast lumps, severe headaches, chest pain, leg swelling, or shortness of breath immediately.
- DONT take Tibolone if you are pregnant, planning pregnancy, or breastfeeding.
- DONT smoke, as smoking significantly increases the risk of serious cardiovascular side effects.
- DONT take other medicines, including herbal supplements (especially St. John's Wort), without consulting your doctor.
8. Toxicology & Storage
Overdose: Acute overdose is unlikely to be life-threatening. Symptoms may include nausea, vomiting, and vaginal bleeding in women. In children, accidental ingestion could cause signs of precocious puberty.
Storage: Store below 30°C. Protect from light and moisture. Keep the blister strips in the outer carton. Keep out of reach and sight of children.