Norethisterone

What is norethisterone?

Norethisterone is a synthetic progestogen. Different products have different indications and chemical forms. This article retains the period-delay subject but identifies the UK Primolut N 5 mg norethisterone tablet as the source for that regimen.

Spain’s Primolut-Nor 5 mg and 10 mg tablets contain norethisterone acetate. Their authorised indications are secondary amenorrhoea and endometriosis, not postponement of menstruation. The UK regimen must not be transferred to those products or treated as proof of Spanish supply.

How does it work?

Progestogenic activity influences the uterine lining. Withdrawal of the hormone can trigger bleeding. With the UK period-delay course, bleeding usually follows 2–3 days after stopping, but spotting or failure to delay can occur.

This is not a reliable contraceptive regimen. Norethisterone can affect ovulation under other regimens; it is inaccurate to claim it never does so. It is partly converted to ethinylestradiol, so the label includes relevant oestrogen-related clot warnings.

Who can be assessed?

A clinician may assess a short-term request to postpone bleeding, for example around travel or sport. The actual product, jurisdiction, pregnancy risk and medical history determine whether any prescription is appropriate. Wanting a delay does not establish eligibility.

For UK Primolut N, do not use with:

• Allergy to a component, known or suspected pregnancy, or breastfeeding.
• Previous idiopathic or current venous thromboembolism, active or recent arterial thromboembolic disease, previous or current warning symptoms of thrombosis, or a high clot risk.
• Migraine with focal neurological symptoms or diabetes with vascular complications.
• Severe liver disease until liver tests normalise, previous or current liver tumours, or pregnancy-related idiopathic jaundice or severe itching.
• Known, past or suspected sex hormone-dependent cancer, unexplained genital bleeding or untreated endometrial hyperplasia.
• Concomitant medicines containing ombitasvir/paritaprevir/ritonavir and dasabuvir.

A family history of thrombosis needs assessment. A strong family history or suspected inherited predisposition requires investigation and may preclude use until evaluated; it is not a blanket diagnosis for every relative’s clot. Smoking, obesity, age, immobility and planned surgery also affect risk.

UK period-delay regimen

This table describes UK Primolut N only and is not a self-prescribing instruction.

Swallow with liquid and follow the prescriber’s instructions. Do not extend treatment because bleeding has not occurred. Exclude pregnancy before another course if the expected bleed fails to occur. The indication is not intended for children. No Spanish acetate or other product dosing is supplied here.

Side effects

In the UK Primolut N label, headache, nausea and oedema are common; migraine is uncommon. Aggravated depression, dizziness and abdominal pain have unknown frequency. The label’s very-common bleeding/spotting classification concerns endometriosis treatment and must not be transferred as a period-delay incidence.

Seek advice about troublesome bleeding or mood changes. Previous depression needs monitoring; stop and contact the prescriber if serious depression recurs.

Stop and seek urgent help

Stop Primolut N and obtain urgent medical assessment for possible clot symptoms: new painful leg swelling, sudden breathlessness, chest pain, sudden weakness or speech difficulty. New migraine-type or unusually severe headaches, sudden vision/hearing changes, jaundice or a substantial blood-pressure increase also require stopping and prompt assessment. Severe allergy requires emergency care.

Tell the clinician well before planned surgery or prolonged immobility so they can arrange interruption and safe resumption if appropriate. Pregnancy requires stopping and contacting the prescriber.

Distinction from Utrogestan

Utrogestan contains progesterone, not norethisterone. Spain’s Utrogestan 200 mg vaginal capsules have assisted-reproduction and selected preterm-birth prevention indications. They are not an authorised period-delay substitute. Other oral progesterone products have their own indications. “Natural” or “bioidentical” does not establish better clot, breast or mood safety for period delay.

Interactions and precautions

Provide a complete medication and supplement list. Enzyme-inducing medicines such as carbamazepine, phenytoin or rifampicin, and St John’s wort, can alter bleeding control and efficacy. HIV/HCV medicines, azole antifungals and other enzyme inhibitors can alter hormone exposure. Norethisterone can also affect medicines such as ciclosporin and lamotrigine. The contraindicated HCV combination above is a restriction on coadministration, not an instruction to stop HCV treatment yourself.

Mention depression, diabetes, migraine, epilepsy, asthma and heart or kidney disease. Fluid retention may aggravate some conditions. Primolut N contains lactose; specified hereditary sugar-intolerance disorders preclude use. Use suitable non-hormonal contraception if required, as agreed with the clinician.

Accessing independent advice

Prescrivia is a technology intermediary connecting patients with independent doctors. It does not prescribe, employ doctors or sell medicines. A doctor assesses the actual product and request; a licensed pharmacy assesses any dispensing under applicable rules. No prescription, period delay or product availability is guaranteed.

In Spain, distance sale of prescription medicines is prohibited under Article 3.5 of Royal Legislative Decree 1/2015. An online assessment does not remove this restriction. Dispensing and access depend on the exact product and applicable national rules.

Sources

• Bayer: UK Primolut N SmPC, sections 2 and 4.1–4.8.
• AEMPS CIMA: Primolut-Nor, sections 2 and 4.1–4.3.
• AEMPS CIMA: Utrogestan 200 mg vaginal capsules, sections 4.1–4.4.

Read the actual product leaflet; this selected information does not replace individual advice.