Relifex (Nabumetone)
Non-steroidal anti-inflammatory drug (NSAID) for osteoarthritis pain and stiffness
Quick Facts About Relifex
Key Takeaways About Relifex
- Once-daily NSAID: Nabumetone's long half-life (22–30 hours) allows convenient once-daily dosing for osteoarthritis
- Prodrug with GI advantage: Nabumetone is a prodrug metabolized in the liver, which may offer a somewhat lower risk of direct gastric irritation compared to some traditional NSAIDs
- Use the lowest effective dose: To minimize the risk of cardiovascular and gastrointestinal side effects, always use the lowest dose for the shortest duration needed
- Not suitable in late pregnancy: Relifex must not be taken during the last three months of pregnancy due to risks of fetal harm and delivery complications
- Consult your doctor if elderly: Patients over 65 should start with a lower dose (500 mg once daily) and be monitored closely for side effects
What Is Relifex and What Is It Used For?
Relifex (nabumetone) is a non-steroidal anti-inflammatory drug (NSAID) used in adults to treat stiff and painful joints caused by osteoarthritis. It works by inhibiting the production of prostaglandins, substances that promote inflammation, pain, and swelling in the body.
Relifex belongs to the class of medicines known as NSAIDs (non-steroidal anti-inflammatory drugs). These are among the most widely prescribed and used medications worldwide for managing pain and inflammation. NSAIDs work by blocking cyclooxygenase (COX) enzymes, which are responsible for producing prostaglandins. Prostaglandins are chemical messengers that play a key role in the inflammatory process, causing swelling, redness, heat, and pain at sites of tissue damage or irritation.
What makes nabumetone somewhat unique among NSAIDs is that it is a prodrug. This means that nabumetone itself is not pharmacologically active. After oral administration, it is absorbed from the gastrointestinal tract and then rapidly metabolized in the liver to its active form, 6-methoxy-2-naphthylacetic acid (6-MNA). It is 6-MNA that actually inhibits the COX enzymes and provides the anti-inflammatory and analgesic effects. Because the parent compound is non-acidic and non-active in the stomach, nabumetone may cause somewhat less direct irritation to the gastric mucosa compared to traditional acidic NSAIDs such as aspirin or indomethacin.
Relifex is specifically indicated for the management of osteoarthritis (also known as degenerative joint disease or arthrosis) in adults. Osteoarthritis is the most common form of arthritis, affecting hundreds of millions of people worldwide. It occurs when the protective cartilage that cushions the ends of bones gradually wears down over time, leading to pain, stiffness, swelling, and decreased range of motion in the affected joints. The knees, hips, hands, and spine are most commonly affected.
By reducing the production of prostaglandins at the site of inflammation, Relifex helps to alleviate the pain, reduce swelling, and improve joint mobility in patients with osteoarthritis. The pain-relieving effect develops gradually over the course of treatment. It is important to note that while Relifex effectively manages symptoms, it does not cure osteoarthritis or reverse cartilage damage. It is a symptomatic treatment that helps patients maintain quality of life and functional ability.
If you are over 65 years of age, consult your doctor before starting treatment with Relifex. Older adults may be more susceptible to side effects, particularly gastrointestinal bleeding and cardiovascular events. A lower starting dose is generally recommended.
How does nabumetone work in the body?
After you swallow a Relifex tablet, nabumetone is absorbed from the small intestine and transported to the liver via the portal circulation. In the liver, it undergoes first-pass metabolism and is converted to 6-MNA, the pharmacologically active metabolite. 6-MNA has a long elimination half-life of approximately 22 to 30 hours, which is the reason Relifex can be taken just once daily, unlike many other NSAIDs that require multiple doses throughout the day.
6-MNA inhibits the cyclooxygenase enzymes (both COX-1 and COX-2), thereby reducing the synthesis of prostaglandins. In inflamed joints, this translates to decreased swelling, reduced pain, and improved stiffness. Peak plasma concentrations of 6-MNA are typically reached within 2.5 to 4 hours after oral administration, and the therapeutic benefit builds over several days of consistent dosing.
What Should You Know Before Taking Relifex?
Do not take Relifex if you are allergic to nabumetone, have active peptic ulcers, severe liver or kidney disease, severe heart failure, or are in the last three months of pregnancy. Always inform your doctor about all medications you take and any existing medical conditions before starting treatment.
Contraindications
There are several situations in which Relifex must not be used. Understanding these contraindications is essential for safe use of this medication. Do not take Relifex if any of the following apply to you:
- Allergy to nabumetone or any of the other ingredients in the tablet
- History of allergic reactions to NSAIDs or aspirin, including asthma, skin rashes, hives, or other allergic symptoms triggered by acetylsalicylic acid or other NSAIDs
- Increased bleeding tendency (bleeding disorders)
- Active peptic ulcer or duodenal ulcer, or a history of ulcers caused by nabumetone or similar drugs
- Recurrent peptic ulcers, duodenal ulcers, or gastrointestinal disease
- Severely impaired liver function, severe heart failure, or severe kidney disease
- Last three months of pregnancy
- Breastfeeding
- Active cerebral hemorrhage or other active bleeding
Do not take Relifex together with other NSAIDs (such as ibuprofen, naproxen, or diclofenac) unless specifically instructed by your doctor. Combining NSAIDs significantly increases the risk of serious gastrointestinal bleeding and other adverse effects. Higher doses than recommended can also lead to serious health risks.
Warnings and Precautions
Even if none of the contraindications above apply to you, there are important precautions to be aware of. Always aim to use the lowest effective dose for the shortest possible duration to minimize the risk of side effects. Talk to your doctor or pharmacist before taking Relifex if you have or have had any of the following conditions:
- Connective tissue diseases such as systemic lupus erythematosus (SLE) or mixed connective tissue disease (MCTD)
- Impaired kidney or liver function
- Heart failure or high blood pressure
- Asthma
- Inflammatory bowel disease such as ulcerative colitis or Crohn's disease
- History of peptic or duodenal ulcers
- Bleeding disorders or conditions with increased bleeding tendency
- Fluid retention (edema)
Older adults should be particularly vigilant about the increased risk of side effects that accompanies advancing age. Especially at the beginning of treatment, patients who have previously experienced gastrointestinal symptoms should monitor for any abdominal discomfort and contact their doctor promptly if symptoms occur.
Medicines like Relifex may be associated with a small increased risk of heart attack or stroke. This risk is more likely with high doses and long-term use. Do not exceed the recommended dose or treatment duration (two weeks for OTC use). Consult your doctor if you have heart problems, a history of stroke, high blood pressure, diabetes, high cholesterol, or if you smoke.
Stop taking Relifex and seek immediate medical attention if you experience swelling of the face, tongue, or throat, difficulty swallowing, or hives combined with breathing difficulties (angioedema). Similarly, stop the medication and see your doctor if you develop a skin rash or damage to mucous membranes, as serious skin reactions have been reported in very rare cases with NSAID use.
Like other NSAIDs, Relifex may mask the signs and symptoms of infection, making it harder to detect an underlying infectious process. It should not be used during chickenpox (varicella). If you experience blurred vision or impaired eyesight during treatment, inform your doctor.
Pregnancy and Breastfeeding
If you are pregnant, breastfeeding, think you may be pregnant, or are planning to have a baby, consult your doctor or pharmacist before taking this medicine. The use of Relifex during pregnancy and breastfeeding requires careful consideration of risks and benefits.
Pregnancy: Relifex must not be taken during the last three months of pregnancy, as it may harm your unborn baby or cause complications during delivery. Specifically, it can cause kidney and heart problems in the fetus, affect bleeding tendency in both mother and baby, and lead to delayed or prolonged labor. During the first six months of pregnancy, Relifex should only be used if absolutely necessary, at the lowest possible dose, and for the shortest possible time. From the 20th week of pregnancy onward, prolonged use may cause low amniotic fluid levels (oligohydramnios) or premature closure of the ductus arteriosus in the baby's heart.
Breastfeeding: It is not known whether nabumetone passes into breast milk. Relifex should not be taken while breastfeeding. Your doctor will advise whether to stop taking Relifex or to stop breastfeeding.
Fertility: Like all medicines that inhibit cyclooxygenase and prostaglandin synthesis, Relifex may make it more difficult to become pregnant. If you are planning a pregnancy or having difficulty conceiving, discuss this with your doctor.
Driving and using machines
Dizziness, confusion, and drowsiness may occur during treatment with Relifex. If you experience any of these symptoms, do not drive or operate machinery. You are personally responsible for assessing whether you are fit to drive or perform work requiring alertness.
Sodium content
This medicine contains less than 1 mmol (23 mg) sodium per tablet, meaning it is essentially sodium-free and suitable for patients on sodium-restricted diets.
How Does Relifex Interact with Other Drugs?
Relifex can interact with many commonly used medications, including blood thinners (warfarin), methotrexate, lithium, blood pressure medications, corticosteroids, SSRIs, and other NSAIDs. Always tell your doctor about all medications you take, including over-the-counter drugs and herbal remedies.
Drug interactions can alter how Relifex works or increase the risk of serious side effects. Some interactions may require dose adjustments, additional monitoring, or avoidance of certain combinations altogether. The following table summarizes the most important known interactions with Relifex. This is not an exhaustive list, so always inform your healthcare provider about every medication you are currently taking.
| Drug / Class | Interaction Effect | Risk Level | Recommendation |
|---|---|---|---|
| Warfarin, ticlopidine (anticoagulants) | Increased anticoagulant effect and bleeding risk | High | Monitor INR closely; dose adjustment may be needed |
| Methotrexate | Reduced renal clearance of methotrexate; increased toxicity | High | Avoid combination or monitor methotrexate levels closely |
| Lithium | Increased lithium plasma levels and risk of toxicity | High | Monitor lithium levels; dose adjustment may be needed |
| ACE inhibitors, ARBs, beta-blockers, diuretics | Reduced antihypertensive effect; increased risk of renal impairment | Moderate | Monitor blood pressure and kidney function |
| SSRIs (antidepressants) | Increased risk of gastrointestinal bleeding | Moderate | Consider gastroprotective therapy |
| Corticosteroids | Increased risk of GI ulceration and bleeding | Moderate | Use gastroprotective agent if combination is necessary |
| Ciclosporin, tacrolimus | Increased nephrotoxicity | High | Monitor renal function closely |
| Other NSAIDs | Additive risk of GI and cardiovascular side effects | High | Avoid combination |
| Cardiac glycosides (digoxin) | Increased plasma levels of cardiac glycosides | Moderate | Monitor digoxin levels |
| Quinolone antibiotics | Possible increased risk of seizures | Moderate | Use with caution |
| Mifepristone | NSAIDs may reduce the effect of mifepristone | Moderate | Avoid NSAIDs for 8-12 days after mifepristone |
Alcohol and Relifex
Concurrent use of alcohol with Relifex can increase the risk of gastrointestinal bleeding and ulceration. Alcohol irritates the stomach lining on its own, and when combined with an NSAID, this irritation is compounded. Additionally, alcohol may exacerbate the drowsiness and dizziness that can occur with nabumetone. It is advisable to limit or avoid alcohol consumption while taking Relifex.
Food and Relifex
Relifex can be taken with or without food. However, taking it with food or milk may help reduce the risk of stomach upset. The absorption of nabumetone is not significantly affected by food, though some studies suggest that taking it with food may slightly increase the bioavailability of the active metabolite 6-MNA.
What Is the Correct Dosage of Relifex?
The standard adult dose is two 500 mg tablets (1,000 mg total) taken once daily. Patients over 65 years should start with one 500 mg tablet once daily. The pain-relieving effect develops gradually. Do not exceed the recommended dose, and consult your doctor if symptoms have not improved within two weeks.
Always take Relifex exactly as described in the patient information leaflet or as directed by your doctor or pharmacist. One of the key advantages of nabumetone is its long half-life, which allows for convenient once-daily dosing. This can improve adherence compared to NSAIDs that require multiple daily doses.
| Patient Group | Dose | Frequency | Notes |
|---|---|---|---|
| Adults (18–64 years) | 1,000 mg (2 × 500 mg) | Once daily | Do not exceed recommended dose |
| Elderly (over 65 years) | 500 mg (1 × 500 mg) | Once daily | Consult doctor before starting; higher risk of side effects |
Adults
The recommended dose for adults aged 18 to 64 years is two tablets of 500 mg taken once daily, for a total daily dose of 1,000 mg. The tablets should be swallowed whole with a glass of water. They can be taken at any time of day, but taking them at the same time each day helps ensure consistent blood levels of the active metabolite.
The analgesic (pain-relieving) effect of nabumetone develops gradually over the course of treatment. Higher doses do not provide greater efficacy, so it is important not to exceed the recommended dose. The minimum effective dose should always be used for the shortest duration necessary to control symptoms.
Children
Relifex is not recommended for use in children and adolescents under 18 years of age. The safety and efficacy of nabumetone in pediatric populations have not been established. Alternative treatments should be considered for younger patients with musculoskeletal pain or inflammatory conditions.
Elderly
Patients over 65 years of age should start with a reduced dose of one 500 mg tablet once daily. Older adults are at increased risk of NSAID-related adverse effects, including gastrointestinal bleeding, renal impairment, and cardiovascular events. The doctor should carefully weigh the benefits of treatment against the risks and may recommend additional monitoring, such as periodic blood tests to check kidney and liver function.
Missed dose
If you forget to take a dose of Relifex, take it as soon as you remember. However, if it is nearly time for your next scheduled dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a forgotten one.
Overdose
If you have taken more Relifex than you should, or if a child has accidentally ingested the medication, contact a poison control center or seek emergency medical attention immediately. Symptoms of overdose may include nausea, vomiting, abdominal pain, drowsiness, and in severe cases, gastrointestinal bleeding or renal impairment. There is no specific antidote for nabumetone overdose; treatment is supportive and symptomatic.
If your condition has not improved within two weeks of starting Relifex, consult your doctor. Continued symptoms may indicate the need for alternative treatment or further diagnostic evaluation. Do not increase the dose on your own.
What Are the Side Effects of Relifex?
Like all medicines, Relifex can cause side effects, although not everybody gets them. Common side effects include diarrhea, indigestion, stomach pain, nausea, edema, drowsiness, itching, and rash. Rare but serious side effects include gastrointestinal bleeding, liver failure, severe skin reactions, and kidney problems. Seek immediate medical attention if you experience signs of a severe allergic reaction.
Side effects are classified by frequency based on how often they are observed in clinical studies and post-marketing surveillance. Understanding these frequencies helps you assess the likelihood of experiencing a particular side effect. However, individual responses to medication vary, and the occurrence of side effects depends on many factors, including age, overall health, and concurrent medications.
Common
May affect up to 1 in 10 patients
- Diarrhea
- Indigestion (dyspepsia) with acid reflux
- Stomach pain
- Gastritis (stomach inflammation)
- Nausea
- Flatulence (gas)
- Constipation
- Blood in the stool
- Edema (fluid retention in tissues)
- Drowsiness
- Itching
- Skin rash
- Blurred vision
- Tinnitus (ringing in the ears)
- Elevated blood pressure
Uncommon
May affect up to 1 in 100 patients
- Shortness of breath
- Anxiety, depression
- Peptic ulcer, duodenal ulcer
- Photosensitivity (sun sensitivity)
- Hives (urticaria), excessive sweating
- Confusion, nervousness, drowsiness
- Fatigue, weakness, dizziness, headache
- Tingling or numbness (paresthesia), insomnia
- Visual disturbances
- Nosebleed, gastrointestinal bleeding
- Black stool, vomiting
- Elevated liver function tests
- Muscle disorders, urinary tract disturbances
- Mouth inflammation, dry mouth
Very Rare
May affect up to 1 in 10,000 patients
- Decreased platelet count (thrombocytopenia)
- Hypersensitivity reactions
- Pneumonitis (lung inflammation)
- Liver failure, jaundice
- Angioedema (swelling of face, lips, tongue, throat)
- Hair loss (alopecia)
- Severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis)
- Skin changes with blistering (pseudoporphyria)
- Kidney failure, kidney impairment
- Heavy menstrual bleeding
- DRESS syndrome (drug reaction with eosinophilia and systemic symptoms)
Not Known
Frequency cannot be estimated from available data
- High blood pressure, heart failure
- Edema (fluid retention)
- Bloody vomit, black stool
- Inflammation of stomach lining
- Oral ulceration
- Worsening of colitis or Crohn's disease
- Various forms of anemia
- Hallucinations
- Meningitis (inflammation of brain membranes)
Swelling of the face, lips, tongue, or throat; difficulty breathing or swallowing; widespread skin rash with fever; severe abdominal pain with bloody or black stools; chest pain or signs of heart attack or stroke (sudden weakness on one side of the body, difficulty speaking, sudden severe headache).
In rare cases, serious skin infections have been reported in connection with chickenpox. NSAIDs including nabumetone, particularly at high doses and with long-term use, may be associated with a small increased risk of myocardial infarction (heart attack) or stroke. If you experience dry mouth as a side effect, maintaining careful oral hygiene is important, including brushing with fluoride toothpaste twice daily, as dry mouth can increase the risk of dental problems.
Reporting side effects
Reporting suspected side effects after the medicine has been authorized is important. It allows continued monitoring of the benefit-risk balance of the medicine. You can report suspected side effects to your national medicines regulatory authority.
How Should You Store Relifex?
Store Relifex out of the sight and reach of children. Do not use after the expiry date stated on the packaging. Do not dispose of medicines in wastewater or household waste – ask your pharmacist for proper disposal methods.
Proper storage of medications is essential to maintain their effectiveness and safety. Relifex should be stored under the following conditions:
- Keep out of sight and reach of children at all times. Accidental ingestion by children can be dangerous.
- Do not use after the expiry date (marked as "EXP" on the packaging). The expiry date refers to the last day of that month.
- Store at room temperature in a dry place, away from direct sunlight and excessive heat.
- Keep the tablets in their original packaging to protect them from moisture.
Do not dispose of medicines via wastewater or household waste. These measures help protect the environment. Ask your pharmacist how to dispose of medicines you no longer use. Many pharmacies and local waste authorities offer medication take-back programs for safe disposal.
What Does Relifex Contain?
The active ingredient is nabumetone (500 mg per tablet). Inactive ingredients include sodium starch glycolate, sodium lauryl sulfate, hypromellose, microcrystalline cellulose, saccharin sodium, macrogol, titanium dioxide (E 171), and caramel flavoring. The tablet is white and oblong in shape.
Active ingredient
Each film-coated tablet contains 500 mg of nabumetone as the active substance. Nabumetone is a non-acidic NSAID prodrug that belongs to the chemical class of 2-naphthyl alkanones. Its chemical name is 4-(6-methoxy-2-naphthyl)-2-butanone, and it has a molecular weight of 228.29 g/mol.
Inactive ingredients (excipients)
The inactive ingredients serve various purposes in the tablet formulation, such as aiding disintegration, providing a smooth coating, and improving palatability:
- Sodium starch glycolate – disintegrant that helps the tablet break apart in the stomach
- Sodium lauryl sulfate – surfactant that aids drug dissolution
- Hypromellose – film-coating agent and binder
- Microcrystalline cellulose – filler and binder
- Saccharin sodium – sweetener
- Macrogol – plasticizer for the film coating
- Titanium dioxide (E 171) – white coloring agent
- Caramel flavoring – taste masking agent
Appearance and packaging
Relifex tablets are white, oblong, film-coated tablets. They are available in blister packs of 30 tablets (over-the-counter) and 20 or 100 tablets (prescription). Not all pack sizes may be marketed in every country.
The marketing authorization holder is Viatris AB. The tablets are manufactured by Haupt Pharma Wuelfing GmbH in Gronau, Germany.
Frequently Asked Questions About Relifex
Relifex (nabumetone) is used to treat pain, stiffness, and swelling in the joints caused by osteoarthritis in adults. It belongs to the NSAID class of medications and works by reducing the production of prostaglandins, which are substances that cause inflammation. It is taken once daily as a 500 mg film-coated tablet, with the standard adult dose being 1,000 mg (two tablets).
The most common side effects (affecting up to 1 in 10 patients) include diarrhea, indigestion, stomach pain, gastritis, nausea, flatulence, constipation, edema, drowsiness, itching, skin rash, blurred vision, tinnitus, and elevated blood pressure. Most of these are mild to moderate and may improve as your body adjusts to the medication. Contact your doctor if any side effect persists or becomes bothersome.
Relifex must not be taken during the last three months of pregnancy as it can cause serious harm to the unborn baby and complications during delivery, including kidney and heart problems in the fetus. During the first six months, it should only be used if absolutely necessary and at the lowest possible dose. From week 20, prolonged use may lead to low amniotic fluid levels. Always consult your doctor before taking any NSAID during pregnancy.
Relifex can significantly increase the anticoagulant effect of blood thinners such as warfarin and ticlopidine, raising the risk of serious bleeding. If you take anticoagulants, your doctor must closely monitor your clotting parameters (INR) and may need to adjust your warfarin dose. Never start or stop Relifex without informing your doctor if you are on blood-thinning medication.
No. While both are NSAIDs, they are different medications. Nabumetone (Relifex) is a prodrug with a long half-life of 22-30 hours that allows once-daily dosing, whereas ibuprofen typically needs to be taken every 4-6 hours. Nabumetone may have a somewhat lower risk of direct gastric irritation because it is non-acidic and inactive in the stomach. However, both carry similar cardiovascular and gastrointestinal risks as a class.
If you or someone else has taken too much Relifex, contact a poison control center or seek emergency medical attention immediately. Overdose symptoms may include nausea, vomiting, stomach pain, drowsiness, and in severe cases, gastrointestinal bleeding or kidney problems. There is no specific antidote; treatment is supportive and aimed at managing symptoms.
References
All information in this article is based on the following authoritative medical sources:
- European Medicines Agency (EMA). Nabumetone – Summary of Product Characteristics. EMA Product Database. Available at: www.ema.europa.eu
- World Health Organization (WHO). WHO Model List of Essential Medicines, 23rd List (2023). Geneva: WHO.
- British National Formulary (BNF). Nabumetone. NICE BNF. Available at: bnf.nice.org.uk
- Friedel HA, Todd PA. Nabumetone: A preliminary review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in rheumatic diseases. Drugs. 1988;35(5):504-524. doi:10.2165/00003495-198835050-00004
- Hedner T, Samulesson O, et al. Nabumetone: therapeutic use and safety profile in the management of osteoarthritis and rheumatoid arthritis. Drugs. 2004;64(20):2315-2343.
- Patrignani P, Tacconelli S, Bruno A, Sostres C, Lanas A. Managing the adverse effects of nonsteroidal anti-inflammatory drugs. Expert Rev Clin Pharmacol. 2011;4(5):605-621.
- U.S. Food and Drug Administration (FDA). NSAIDs Drug Safety Communication: FDA strengthens warning. Available at: www.fda.gov
- Coxib and traditional NSAID Trialists' (CNT) Collaboration. Vascular and upper gastrointestinal effects of non-steroidal anti-inflammatory drugs: meta-analyses of individual participant data from randomised trials. Lancet. 2013;382(9894):769-779.
Medical Editorial Team
This article has been written and reviewed by the iMedic Medical Editorial Team, consisting of licensed specialist physicians in pharmacology, rheumatology, and internal medicine. Our team follows international guidelines from the WHO, EMA, and FDA, and adheres to the GRADE evidence framework to ensure the highest quality of medical information.
All content is reviewed by board-certified physicians with expertise in pharmacology and clinical medicine. Evidence level: 1A (systematic reviews and RCTs).
We follow WHO, EMA, and FDA guidelines. No commercial funding or pharmaceutical company sponsorship influences our content.
GRADE framework applied to all medical claims. Sources include peer-reviewed journals, systematic reviews, and international treatment guidelines.
Content is reviewed and updated regularly to reflect the latest clinical evidence and regulatory changes. Last reviewed: January 2026.