Mefenamic Acid

About Mefenamic Acid

Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) that blocks the prostaglandins behind pain and menstrual cramping. The label approves it for mild to moderate pain in adults and children 14 and older, for no longer than one week, and for primary dysmenorrhea, the painful periods that have no underlying cause. For both uses the dose is 500 mg (two capsules) to start, then 250 mg every six hours as needed; for period pain it is started when bleeding and symptoms begin. The label says to use the lowest effective dose for the shortest time, and MedlinePlus advises taking it with food.

The boxed warning covers two risks shared by prescription NSAIDs: heart attack and stroke, which can be fatal and can occur early in treatment, with the drug contraindicated around coronary artery bypass surgery; and bleeding, ulcers and perforation of the stomach or intestine, which can happen without warning and are more likely in older people and with past ulcers. Mefenamic acid must not be taken by anyone who has had asthma, hives or an allergic reaction to aspirin or another NSAID. Other warnings cover liver injury, raised blood pressure, heart failure and swelling, kidney injury and high potassium, severe skin reactions, a drug reaction with eosinophilia and systemic symptoms (DRESS), and effects on blood counts. The common side effects are stomach upset, abdominal pain, diarrhea or constipation, nausea, heartburn, dizziness, headache, rash and ringing in the ears.

What is distinctive is the pregnancy advice and the short course. The label says to avoid NSAIDs at about 30 weeks of pregnancy and later, because they can close a blood vessel in the baby’s heart early, and that use at about 20 weeks or later can reduce the baby’s kidney function and the fluid around the baby. The one-week limit for pain is a label limit, not a suggestion, so a prescription is written for a small number of capsules. Mefenamic acid adds to the bleeding risk of warfarin, other blood thinners, SSRIs and SNRIs, blunts the effect of ACE inhibitors, ARBs and diuretics, and raises lithium and methotrexate levels; it is not taken with other NSAIDs or with aspirin for pain. It is not a controlled substance.

Taking Mefenamic Acid

How to take it

Take it by mouth with food exactly as prescribed: two capsules to start, then one every six hours as needed, for no more than a week. Use the lowest dose for the shortest time, and do not take it with other NSAIDs or with aspirin for pain.

If you miss a dose

Take it as soon as you remember, unless it is almost time for the next dose; then skip the missed dose. Do not take a double dose.

Storage

In the original tightly closed container at room temperature, away from heat and moisture, out of reach of children.

Interactions to know about

Warfarin and other anticoagulants, antiplatelet drugs, SSRIs and SNRIs raise the bleeding risk; ACE inhibitors, ARBs, beta blockers and diuretics may work less well and the kidneys can suffer; lithium, methotrexate, digoxin and cyclosporine levels or toxicity can rise. Avoid other NSAIDs and aspirin for pain, and tell the pharmacist about every medicine you take.

This summarizes the official prescribing information. Your prescriber’s and pharmacist’s instructions, and the leaflet that comes with your medicine, take priority.

Why the cash price for Mefenamic Acid differs from pharmacy to pharmacy

Mefenamic acid is a short-course drug, so a quote is for a small count of capsules, and the dispensing fee is a large share of it; whether the pharmacy has it on a flat-price generic list matters more than the maker, and not every pharmacy keeps it on the shelf.

Capsules come in bottles of 30 and 100, so a pharmacy may quote from the pack it stocks rather than the count written; ask for a quote on the exact number on the prescription, and expect a prescription for the Ponstel brand without substitution to be priced as a brand.

Ways to pay less for Mefenamic Acid without insurance

• Ask the pharmacy whether mefenamic acid is on its flat-price generic list, and ask for a quote on the exact number of capsules written.
• Compare more than one pharmacy, and ask whether yours stocks it or would need to order it; for period pain that starts the same day, stocking matters.
• If the quote is high, ask the prescriber whether a generic NSAID the pharmacy always stocks, such as naproxen or ibuprofen, would suit you instead; do not switch on your own.
• Ask for only the quantity your course needs, since the label limits pain treatment to one week.
• Upload the prescription to Script Unlock so licensed pharmacies can quote their cash price. You pay the pharmacy directly.

Questions to ask your pharmacist about Mefenamic Acid

1. 1.How many days can I take my mefenamic acid, and should I take it with food?
2. 2.Can I take it with my blood pressure pills, my blood thinner or my antidepressant?
3. 3.Which symptoms, such as black stools, chest pain or swelling, mean I should stop it and get help?
4. 4.Is it safe for me if I could be pregnant, and at what point in pregnancy must I avoid it?

Related medications