Ospemifene
A SERM and active metabolite of toremifene, approved for dyspareunia from vulvovaginal atrophy. It shows oestrogen-agonist activity on vaginal and bone tissue while antagonising breast, and has been explored as a PCT-style gonadotropin stimulant.
01 Overview
Ospemifene (Osphena/Senshio) is a triphenylethylene SERM and a des-chloro metabolite of toremifene. It is licensed for moderate-to-severe dyspareunia caused by postmenopausal vulvovaginal atrophy, where it acts as an oestrogen agonist on vaginal epithelium.
Because it raises gonadotropins by blocking central oestrogen feedback in men, it is occasionally repurposed off-label as an HPTA-restart agent, though clinical data in that setting are limited compared with tamoxifen or clomifene.
02 Mechanism
Tissue-selective oestrogen receptor modulator: agonist in vaginal and bone tissue, antagonist in breast and (centrally) at the hypothalamus, raising LH/FSH and testosterone in men.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Off-label restart | 30–60 mg/day | Oral | Anecdotal PCT dosing; limited evidence. |
| Dyspareunia | 60 mg/day | Oral | Licensed dose taken with food. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Raised gonadotropinsCentral oestrogen antagonism releases the pituitary from negative feedback. | LH/FSH increase in men | Clinical | |
| Bone density preservationRetains agonist activity in skeletal tissue, unlike aromatase inhibitors. | Oestrogen-agonist on bone | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Hot flashesMost common labelled adverse effect. | Mild | Common | Clinical | |
| Venous thromboembolismClass thrombotic risk carried by all triphenylethylene SERMs. | Severe | Rare | Clinical |