Naproxen tablets contain one active ingredient, naproxen (or its faster-absorbing salt form, naproxen sodium), plus a handful of inactive ingredients that hold the pill together, coat it, and give it color. The active drug is a nonsteroidal anti-inflammatory (NSAID) that works by blocking the enzymes responsible for pain and inflammation. Here’s a closer look at everything inside the tablet and what each component does.
The Active Ingredient
The only medicine in a naproxen tablet is naproxen itself. It belongs to the propionic acid family of NSAIDs, the same chemical group as ibuprofen. Its molecular formula is C₁₄H₁₄O₃, and it’s classified as a non-selective NSAID, meaning it targets two related enzymes in your body: COX-1 and COX-2.
You’ll see two versions on store shelves. Plain naproxen (sold under the brand name Naprosyn) is the base form. Naproxen sodium (the form in Aleve and most generic OTC tablets) adds a sodium atom to the molecule, which makes it dissolve and absorb faster, producing higher peak blood levels for the same dose. The chemical formula for naproxen sodium is C₁₄H₁₃NaO₃. If you’ve noticed that OTC naproxen sodium works quickly, that’s the reason.
How the Active Ingredient Works
When tissue is injured or inflamed, your body converts a fatty acid called arachidonic acid into prostaglandins, which are chemical messengers that trigger pain, swelling, and fever. The enzymes that drive this conversion are COX-1 and COX-2. Naproxen blocks arachidonic acid from binding to both enzymes, cutting off prostaglandin production at the source.
COX-2 is the enzyme your body ramps up during inflammation, so blocking it is what reduces pain and swelling. COX-1, on the other hand, runs all the time in most tissues, helping maintain your stomach lining, kidney function, and normal blood clotting. Naproxen is actually slightly more selective for COX-1 than COX-2, which is an important detail for side effects (more on that below) and also for cardiovascular safety.
That COX-1 preference has a practical upside. The American Heart Association and the American College of Gastroenterology have both recommended naproxen as the NSAID of choice for people with high cardiovascular risk. Large analyses show naproxen does not significantly increase the risk of major vascular events or vascular death, unlike some other NSAIDs such as diclofenac. It also doesn’t meaningfully raise systolic blood pressure. The tradeoff is that blocking COX-1 can irritate the stomach lining, which is why naproxen is harder on the gut than COX-2-selective drugs.
Inactive Ingredients in a Typical Tablet
Everything besides naproxen (or naproxen sodium) in the pill is there for structural or cosmetic reasons. These ingredients don’t treat pain. A standard OTC naproxen sodium tablet contains:
- Microcrystalline cellulose: A plant-derived fiber that acts as the main filler, giving the tablet its bulk and shape.
- Corn starch: Helps bind the powder together during manufacturing and aids in breaking the tablet apart once swallowed.
- Sodium starch glycolate: A “super disintegrant” that absorbs water rapidly, causing the tablet to swell and fragment in your stomach so the drug dissolves.
- Povidone: A binder that holds the compressed powder in tablet form so it doesn’t crumble.
- Stearic acid: A lubricant that prevents the tablet mixture from sticking to manufacturing equipment.
- Hypromellose and polyethylene glycol: Together, these form the thin film coating on the outside of the tablet. The coating makes it easier to swallow and can protect the drug from moisture.
- Titanium dioxide: A white pigment used in the coating to give it an opaque appearance.
- FD&C Blue #2 aluminum lake: The dye responsible for the blue color of many naproxen sodium tablets.
These inactive ingredients vary between manufacturers and formulations. A delayed-release or prescription version may include different coatings, and some generics swap out one filler for another. If you have a sensitivity to a specific dye or additive, check the “inactive ingredients” section on your product’s label or look up the specific product on the DailyMed database (dailymed.nlm.nih.gov).
Naproxen Base vs. Naproxen Sodium Tablets
The distinction matters more than most people realize. Because naproxen sodium dissolves faster, it reaches peak blood levels sooner than plain naproxen. That’s why virtually all OTC products use the sodium form: faster onset means quicker relief for a headache or menstrual cramp. Prescription naproxen, on the other hand, sometimes uses the base form or a delayed-release coating designed to protect the stomach by releasing the drug further along in the digestive tract.
Dosing differs slightly between the two. A 220 mg naproxen sodium tablet delivers 200 mg of actual naproxen plus 20 mg of sodium. A 500 mg prescription naproxen tablet is all naproxen. The sodium content is small, but worth knowing if you’re on a sodium-restricted diet and taking multiple doses daily.
How Your Body Processes It
Naproxen is well absorbed from the gut regardless of which form you take. Your liver metabolizes the drug using its cytochrome P450 enzyme system, and the breakdown products are eliminated primarily through the kidneys. Naproxen has a relatively long half-life compared to other OTC pain relievers, which is why it’s typically dosed every 8 to 12 hours rather than every 4 to 6 hours like ibuprofen. That longer action is one of the main reasons people choose it for conditions that cause sustained pain, like arthritis or back injuries.
Why Inactive Ingredients Matter
For most people, inactive ingredients are irrelevant. But if you’ve ever had a reaction to a medication that wasn’t explained by the active drug, an excipient could be the culprit. FD&C Blue #2, for instance, is a synthetic dye that some people prefer to avoid. Corn starch can be a concern for people with rare corn allergies. Titanium dioxide, while widely used in foods and medications, has drawn regulatory scrutiny in the European Union as a food additive, though it remains approved in the U.S. for pharmaceutical use.
If you need a dye-free option, some manufacturers sell naproxen sodium tablets without FD&C Blue #2. Checking the package or asking a pharmacist is the fastest way to find one.