UK Clinical Pharmacy Association

Estradiol with dydrogesterone

Brands of this drug

Femoston®, Femoston Conti® 

Issues for surgery

Risk of menopausal symptoms, e.g. hot flushes, if discontinued pre-operatively.

Reduced protection against osteoporosis if discontinued for prolonged period.

Risk of venous thromboembolism (VTE) if continued.

Advice in the perioperative period

Elective surgery 

Minor surgery

Continue unless there is a risk of prolonged immobilisation – see Major surgery.

Ensure adequate VTE prophylaxis if continued.

Major surgery

Consider stopping 4-6 weeks before major elective surgery where prolonged immobilisation is likely, particularly vascular and orthopaedic lower limb surgery. See Further information

Consider other risk factors that the patient may have that further increase the risk of VTE, e.g. age, weight, previous history of VTE.

Please note, if doses are missed, it may result in breakthrough bleeding.

Emergency surgery 

Ensure adequate thromboprophylaxis to reduce risk of VTE.

If prolonged immobilisation anticipated consider discontinuing on admission.

Please note, if doses are missed, it may result in breakthrough bleeding.

Patients admitted with gallstones (cholelithiasis)

Use of estradiol (with dydrogesterone) can aggravate gallstones in patients who have a previous history of this condition; bear this in mind for patients admitted with gallstones who are on this medication.

Post-operative advice

If stopped pre-operatively restart after full mobilisation.

Patients undergoing major gynaecological surgery

Review appropriateness of restarting this preparation after major gynaecological surgery.

Interactions with common anaesthetic agents


Oestrogens may, potentially, inhibit cytochrome P450 (CYP450) drug-metabolising enzymes via competitive inhibition. In theory, this could affect the metabolism of fentanyl (via CYP3A4) leading to an increased plasma level; hence smaller doses than usual may be required and careful monitoring required. It is unlikely that continued use of this medication perioperatively will have a significant effect on fentanyl; but bear the interaction in mind where there is concomitant use and there is a change in therapeutic effect.


Administration of a single bolus dose of sugammadex is predicted to cause a 34% decrease in progestogen exposure. This predicted pharmacokinetic reaction has not been proven clinically, however bear the potential reaction in mind should breakthrough bleeding be reported after concomitant use.

Interactions with other common medicines used in the perioperative period


Since oestrogen metabolism can be affected by concomitant use of medicines that affect cytochrome P450 enzymes, specifically CYP3A4; the manufacturers note that concomitant use of inducers of CYP3A4, such as dexamethasone, may reduce plasma concentrations of oestrogen, with a possible reduction in therapeutic effect and/or changes in uterine bleeding. It is unlikely that use of dexamethasone perioperatively will have a significant effect, but bear the interaction in mind where there is concomitant use of both medications and there is a change in therapeutic effect.

Further information

Risk of VTE with oral HRT preparations containing oestrogen

During first pass metabolism in the liver oral HRT preparations containing oestrogen affect the clotting cascade by increasing resistance to protein S and protein C (natural anticoagulants) and increasing fibrinogen, thus increasing the risk of thrombosis. Patients taking oral HRT are at increased risk of VTE compared with non-users. The risk is thought to be greatest in the first year of treatment and also in women with an increased body mass index. The baseline risk of VTE also increases substantially with age.

The risk of VTE varies depending on the oestrogen (and progesterone) content of the preparation. Preparations with conjugated equine oestrogen are associated with higher VTE risk compared to those with estradiol. Higher doses of oestrogen are also associated with higher VTE risk. The highest risk is with preparations containing both conjugated equine oestrogen and medroxyprogesterone acetate and the lowest risk is with estradiol with dydrogesterone.


Baxter K, Preston CL (eds), Stockley’s Drug Interactions (online) London: Pharmaceutical Press. [Accessed on 5th January 2024]

Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press. [Accessed on 5th January 2024]

National Institute of Health and Clinical Excellence (2019). NG23 Menopause: diagnosis and management. [Accessed on 5th January 2024]

Summary of Product Characteristics – Femoston® (dydrogesterone, estradiol hemihydrate) 2/10mg Film-coated Tablets. Mylan. Accessed via 05/01/24 [date of revision of the text September 2023]

Summary of Product Characteristics – Sugammadex 100mg/ml solution for injection. Amarox Limited. Accessed via 24/01/24 [date of revision of the text September 2023]

Vinogradova, Y. Coupland, C & Hippisley-Cox, J. Use of hormone replacement therapy and risk of venous thromboembolism: nested case-control studies using the QResearch and CPRD databases. BMJ. 2019; 364: k4810. DOI: 10.1136/bmj.k4810