Naproxen sodium is an over-the-counter and prescription pain reliever that belongs to the NSAID (nonsteroidal anti-inflammatory drug) class. It reduces pain, inflammation, and fever by blocking the enzymes your body uses to produce prostaglandins, the chemicals responsible for swelling, pain signaling, and elevated temperature. Its long duration of action sets it apart from similar drugs like ibuprofen, typically providing relief for 8 to 12 hours per dose.
How Naproxen Sodium Works
Your body contains two enzymes, COX-1 and COX-2, that produce prostaglandins. When you’re injured or sick, prostaglandins trigger inflammation, amplify pain signals, and raise your body temperature. Naproxen blocks both of these enzymes with roughly equal strength, which is why it works as a pain reliever, anti-inflammatory, and fever reducer all at once.
The process isn’t instant. Naproxen initially attaches loosely to the enzyme, then gradually shifts into a tighter bond that holds it in place longer. This time-dependent binding helps explain why the drug’s effects build over the first hour or so and then last for many hours afterward. Unlike aspirin, which permanently disables the enzyme, naproxen’s bond is reversible, so the effect wears off as the drug is cleared from your body.
Naproxen Sodium vs. Plain Naproxen
You’ll see two forms on pharmacy shelves: naproxen (sold as Naprosyn) and naproxen sodium (sold as Aleve, Anaprox, and others). The active ingredient is the same molecule, but the sodium salt form dissolves and absorbs faster, reaching higher peak levels in your blood for a given dose. In practical terms, naproxen sodium kicks in more quickly. That’s why the sodium form is the one you’ll find in most OTC products designed for acute pain like headaches or menstrual cramps.
The dosing numbers differ slightly because the sodium salt adds molecular weight. A 220 mg naproxen sodium tablet delivers the equivalent of 200 mg of naproxen. This doesn’t change anything about how you take it, but it’s worth knowing if you’re comparing labels.
What It’s Used For
Naproxen sodium has a broad range of FDA-approved uses. At prescription strength, it treats chronic inflammatory conditions including rheumatoid arthritis, osteoarthritis, ankylosing spondylitis (an inflammatory arthritis of the spine), and juvenile arthritis. It’s also approved for tendonitis, bursitis, and acute gout flares.
At OTC strength, most people reach for it to manage everyday pain: headaches, muscle aches, backaches, toothaches, and menstrual cramps. Its long half-life makes it especially practical for conditions that cause sustained discomfort, since you only need to dose every 8 to 12 hours instead of every 4 to 6 hours as with ibuprofen.
Typical Dosing
OTC naproxen sodium (Aleve) comes in 220 mg tablets. The standard adult dose is one tablet every 8 to 12 hours, with a maximum of two to three tablets in 24 hours depending on the product label. For the first dose, some labels recommend taking two tablets, then one tablet afterward.
Prescription doses are considerably higher. For arthritis, a common starting regimen is 250 mg to 500 mg twice daily, morning and evening, with a ceiling of 1,500 mg per day. A controlled-release prescription form delivers the drug more gradually, which can help maintain steady levels for chronic conditions.
Side Effects and Risks
The most common side effects are gastrointestinal: stomach pain, nausea, heartburn, and indigestion. Because naproxen blocks COX-1, which helps maintain the protective lining of your stomach, long-term or high-dose use increases the risk of stomach ulcers and GI bleeding. Taking it with food or a full glass of water can reduce stomach irritation, though it doesn’t eliminate the underlying risk.
All NSAIDs, including naproxen sodium, carry FDA label warnings about an increased risk of heart attack and stroke. This risk is higher in people who already have cardiovascular disease and increases with longer use and higher doses. That said, among the commonly used NSAIDs, naproxen has generally been considered one of the more favorable options from a cardiovascular standpoint, which is one reason it remains widely recommended.
Naproxen can also affect kidney function, particularly in people who are dehydrated, elderly, or already have reduced kidney function. It may raise blood pressure and reduce the effectiveness of blood pressure medications. Rarely, it can cause serious allergic reactions, especially in people with a history of asthma triggered by aspirin or other NSAIDs.
Drug Interactions to Know About
Naproxen sodium interacts with a significant number of common medications. Blood thinners are the most important concern: combining naproxen with anticoagulants raises the risk of bleeding because the drug both irritates the stomach lining and interferes with platelet function. Other notable interactions include:
- Blood pressure medications and diuretics: Naproxen can blunt their effectiveness and contribute to fluid retention.
- Other NSAIDs, including aspirin: Stacking multiple NSAIDs increases GI and kidney risks without adding much pain relief.
- Lithium and methotrexate: Naproxen can raise blood levels of both drugs to potentially dangerous concentrations.
- Some antidepressants (SSRIs): The combination increases the chance of GI bleeding.
- Corticosteroids (prednisone, cortisone): Also raises GI bleeding risk when used together.
- Alcohol: Adds to stomach irritation and bleeding risk.
Certain supplements, including garlic, ginger, and ginkgo, may also increase bleeding risk when combined with naproxen.
Pregnancy Concerns
The FDA warns against using naproxen sodium (or any NSAID) at 20 weeks of pregnancy or later. Starting around that point, NSAIDs can impair fetal kidney function, leading to dangerously low amniotic fluid levels. This has been reported in some cases as soon as 48 hours after starting the medication. Prolonged low amniotic fluid can cause limb contractures and delayed lung development in the baby.
After 30 weeks of pregnancy, there’s an additional risk: NSAIDs can cause premature closure of a blood vessel in the fetal heart called the ductus arteriosus, which needs to stay open until birth. For these reasons, naproxen is generally avoided entirely in the second half of pregnancy.
Who Should Be Cautious
Naproxen sodium is a safe and effective option for most adults when used at recommended doses for short periods. But certain groups face higher risks. People with a history of stomach ulcers or GI bleeding should be especially careful, as should those with kidney disease, heart failure, or uncontrolled high blood pressure. If you’ve ever had an asthma attack, hives, or facial swelling after taking aspirin or another NSAID, naproxen can trigger the same reaction.
Older adults are more vulnerable to both the GI and kidney effects, partly because kidney function naturally declines with age and partly because they’re more likely to be on interacting medications. For short-term pain relief in otherwise healthy adults, naproxen sodium remains one of the most widely used and well-studied options available without a prescription.