Mefenamic Acid for Period Pain: The Dual-Action Option
The UK prescription NSAID that reduces both pain and heavy bleeding — how it works, who it suits and when to choose it.
Part of the Access Doctor period pain guide.
Key fact: Mefenamic acid (brand name Ponstan in the UK) is the only commonly prescribed NSAID for period pain with a dual mechanism — it both inhibits prostaglandin synthesis (like ibuprofen and naproxen) and directly blocks prostaglandin receptors. It also reduces menstrual blood loss by 20–30%, making it the preferred choice in UK practice for women with both painful and heavy periods.
Get a UK Prescription for Period Pain Relief
Access Doctor is a GPhC-registered UK online pharmacy. Our pharmacist independent prescribers can assess you and prescribe naproxen 500mg or ibuprofen 600mg for period pain — no GP appointment needed. Discreet UK delivery, usually next working day.
Start UK Consultation →How Mefenamic Acid Works
Mefenamic acid belongs to the fenamate class of NSAIDs and has two distinct actions relevant to period pain:
- COX inhibition — like ibuprofen and naproxen, it inhibits both COX-1 and COX-2 enzymes, reducing the synthesis of prostaglandins from arachidonic acid. This reduces the total prostaglandin load in the uterus.
- Prostaglandin receptor antagonism — uniquely, mefenamic acid also directly blocks prostaglandin receptors, limiting the effect of prostaglandins already present. This dual blockade provides additional pain relief compared to COX inhibition alone.
Additionally, mefenamic acid reduces menstrual blood loss by approximately 20–30% through its effects on prostaglandin-mediated platelet aggregation and uterine vasodilation. This makes it particularly valuable when period pain and heavy bleeding occur together — a pattern that is common in UK primary care and one of the reasons mefenamic acid is specifically named in NICE guidance on heavy menstrual bleeding.
Correct Dose and Timing
| Dose | Timing | Duration | Notes |
|---|---|---|---|
| 500mg three times daily | Every 8 hours with food | For the painful days (2–3 days) | Standard UK prescription dose; max 1,500mg/day |
As with all NSAIDs for period pain: start at the first sign of bleeding or pain. The earlier treatment begins, the more effectively it limits prostaglandin levels before they peak. Always take with food.
Mefenamic acid is prescription only in the UK. Unlike ibuprofen 400mg or naproxen 250mg, there is no over-the-counter formulation available at UK pharmacies. Access Doctor prescribers can assess suitability and issue a private UK prescription online following a short consultation.
Who Mefenamic Acid Suits Best
Painful + heavy periods
The dual prostaglandin-reducing mechanism addresses both components simultaneously. First-line NSAID choice in UK practice when both are problematic.
Inadequate response to ibuprofen/naproxen
The additional prostaglandin receptor blockade gives mefenamic acid a different mechanism that may work better for some women who have not responded to standard NSAIDs.
Secondary dysmenorrhoea (e.g. endometriosis)
In endometriosis-related dysmenorrhoea, prostaglandin activity may be higher than in primary dysmenorrhoea. The receptor-blocking component may provide additional relief.
Mefenamic Acid vs Ibuprofen vs Naproxen
| Feature | Mefenamic acid 500mg | Ibuprofen 600mg | Naproxen 500mg |
|---|---|---|---|
| Mechanism | COX inhibition + prostaglandin receptor block | COX inhibition | COX inhibition |
| Reduces heavy bleeding? | Yes (~20–30%) | Modest | Modest |
| Doses per day | 3 (every 8h) | 3 (every 6–8h) | 2 (every 8–12h) |
| UK availability | Prescription only | OTC at 400mg; Rx at 600mg | OTC at 250mg; Rx at 500mg |
| Best for | Painful + heavy periods; NSAID non-responders | Quick relief; flexible dosing | Sustained all-day relief; fewer doses |
Side Effects and Precautions
- GI symptoms — nausea, diarrhoea, heartburn; common; take with food. Diarrhoea is slightly more common with mefenamic acid than other NSAIDs.
- Headache, dizziness — mild; usually transient
- Haemolytic anaemia — rare; more associated with long-term use. For short 2–3 day courses per cycle, clinically insignificant for most women.
Contraindicated in the same circumstances as all NSAIDs: peptic ulcer disease, significant kidney impairment, aspirin-sensitive asthma, third trimester pregnancy, severe heart failure. Mefenamic acid is additionally not recommended in inflammatory bowel disease. If you are unsure whether mefenamic acid is safe for you, a UK prescriber can assess this during an online consultation.
How to Get Mefenamic Acid in the UK
Mefenamic acid is a prescription-only medicine in the UK. There are two legitimate routes to get it:
- NHS prescription via your GP — if your period pain or heavy bleeding is affecting your daily life, book an appointment with your GP. Mefenamic acid is a standard NHS treatment for dysmenorrhoea and heavy menstrual bleeding, and the prescription is covered by the standard NHS prescription charge (currently £9.90 per item in England; free in Scotland, Wales and Northern Ireland).
- Private UK prescription online — if you would rather not wait for a GP appointment, UK-registered online pharmacies such as Access Doctor can assess you and issue a private prescription following a short online consultation with a GPhC-registered pharmacist independent prescriber.
Mefenamic acid cannot be bought over the counter in the UK — not at Boots, Superdrug, LloydsPharmacy, or any other UK high-street or online pharmacy. Any website offering it without a prescription is operating outside UK medicines regulations and should be avoided.
Through Access Doctor, prescriptions are issued in line with NICE guidance and dispensed from our GPhC-registered UK pharmacy. All medicines are MHRA-licensed UK products. Delivery is UK-only and usually next working day.
Start a UK Consultation
Access Doctor is a GPhC-registered UK online pharmacy (registration number 9011198). Our UK pharmacist independent prescribers can assess you and prescribe prescription-strength period pain relief, dispatched discreetly with next-working-day UK delivery.
Start UK Consultation →Frequently Asked Questions
What is mefenamic acid and how is it different from other NSAIDs?
Mefenamic acid has a dual mechanism: COX inhibition (like ibuprofen/naproxen) plus direct prostaglandin receptor blockade. It also reduces menstrual blood loss by 20–30%. It is prescription-only in the UK, where it is also sold under the brand name Ponstan.
What is the dose of mefenamic acid for period pain?
The standard UK dose is 500mg three times daily with food, starting at the onset of pain or bleeding. Continue for 2–3 painful days. Maximum 1,500mg/day, in line with NICE CKS guidance.
Can mefenamic acid reduce heavy periods as well as pain?
Yes — it reduces blood loss by approximately 20–30% alongside pain relief. It is a first-line NSAID choice in UK practice for women with both painful and heavy periods, as reflected in NICE guidance (NG88).
Is mefenamic acid stronger than ibuprofen or naproxen?
Different rather than simply stronger. Its additional prostaglandin receptor blockade may benefit women who have not responded to ibuprofen or naproxen, and its blood-loss reduction is unique among common NSAIDs.
Can I buy mefenamic acid over the counter in the UK?
No. Mefenamic acid is a prescription-only medicine (POM) in the UK and cannot be bought over the counter at Boots, Superdrug, or any other UK pharmacy. It requires either an NHS prescription from your GP or a private prescription from a UK-registered prescriber such as Access Doctor.
Can I get mefenamic acid on the NHS?
Yes — it is a standard NHS treatment for period pain and heavy periods. Speak to your GP. Alternatively, UK-registered online pharmacies like Access Doctor can issue a private prescription following a short online consultation.
Who should use mefenamic acid instead of ibuprofen or naproxen?
Women with both pain and heavy bleeding, inadequate response to ibuprofen or naproxen, or secondary dysmenorrhoea (e.g. endometriosis). A UK prescriber can assess which is right for you.
References
- National Institute for Health and Care Excellence (NICE). Heavy menstrual bleeding: assessment and management (NG88). 2018 (updated 2023). nice.org.uk/guidance/ng88
- NICE Clinical Knowledge Summaries. Dysmenorrhoea. cks.nice.org.uk/topics/dysmenorrhoea
- Marjoribanks J et al. Nonsteroidal anti-inflammatory drugs for dysmenorrhoea. Cochrane Database Syst Rev. 2015. PubMed: 26224322
- NHS. Mefenamic acid. nhs.uk/medicines/mefenamic-acid
- NHS. Period pain. nhs.uk/conditions/period-pain
Medical disclaimer: This article is for informational purposes only. Period pain can be a symptom of an underlying condition requiring assessment. Prescription medicines require a consultation before they can be dispensed. In a medical emergency call 999.