NSAIDs, short for nonsteroidal anti-inflammatory drugs, are a widely used class of medications that reduce pain, lower fevers, and fight inflammation. You’ve almost certainly taken one: ibuprofen (Advil, Motrin), naproxen (Aleve), and aspirin are all NSAIDs available without a prescription. More than 20 different NSAIDs exist, ranging from inexpensive over-the-counter pills to stronger prescription-only versions.
How NSAIDs Work in Your Body
When tissue is injured or irritated, your body produces chemicals called prostaglandins. These are the molecules that trigger inflammation, amplify pain signals, and raise your temperature during a fever. NSAIDs work by blocking the enzyme (cyclooxygenase, or COX) responsible for making prostaglandins. Less prostaglandin production means less swelling, less pain, and lower fever.
There are two forms of this enzyme. COX-1 is active all the time and helps protect your stomach lining, support kidney function, and promote normal blood clotting. COX-2 ramps up mainly during injury or inflammation. Most common NSAIDs block both forms to varying degrees, which is why they relieve inflammation effectively but can also cause stomach and kidney side effects. Some prescription NSAIDs, like celecoxib (Celebrex), are designed to target COX-2 more selectively, reducing some of the stomach-related risks.
Common Over-the-Counter and Prescription NSAIDs
The three NSAIDs you can buy without a prescription are:
- Ibuprofen (Advil, Motrin)
- Naproxen sodium (Aleve)
- Aspirin (Bayer)
Prescription-strength NSAIDs are typically used for more persistent or severe pain. Common examples include celecoxib (Celebrex), diclofenac (Voltaren), indomethacin (Indocin), fenoprofen (Nalfon), and ketorolac (Toradol). These vary in potency, how long they last, and which COX enzyme they primarily target.
What NSAIDs Treat
NSAIDs are used for both short-term and long-term pain management. For acute pain, they’re a go-to for headaches, menstrual cramps, dental pain, muscle strains, and fevers from illness. For chronic conditions, they’re commonly prescribed for osteoarthritis, rheumatoid arthritis, and ankylosing spondylitis, where ongoing inflammation drives joint pain and stiffness.
The reason NSAIDs are so popular for these conditions is that they don’t just mask pain the way some other painkillers do. They actually reduce the underlying inflammation causing the pain, which makes them particularly effective for anything involving swelling, redness, or irritated tissue.
How Aspirin Differs From Other NSAIDs
Aspirin is technically an NSAID, but it behaves differently in one important way. It permanently disables the COX-1 enzyme in platelets, the blood cells responsible for clotting. Because platelets can’t repair themselves, this anti-clotting effect lasts for the entire lifespan of each affected platelet (roughly 7 to 10 days). That’s why low-dose aspirin is used to prevent heart attacks and strokes in people at high risk.
Other NSAIDs like ibuprofen and naproxen also interfere with clotting, but only temporarily. They bind to COX-1 reversibly, so once the drug clears your system, platelet function returns to normal. This distinction matters: if you take ibuprofen around the same time as low-dose aspirin, the ibuprofen can physically block aspirin from reaching its target on the enzyme, potentially reducing aspirin’s heart-protective benefit.
NSAIDs vs. Acetaminophen
Acetaminophen (Tylenol) is often grouped with NSAIDs in people’s minds, but they’re fundamentally different. Acetaminophen reduces pain and fever, but it does not reduce inflammation. If your pain comes from a swollen joint, a sprained ankle, or menstrual cramping, an NSAID will generally work better because it addresses the inflammation driving the pain. Acetaminophen is processed through the liver rather than affecting the stomach lining, so it’s often a safer choice for people who can’t tolerate NSAIDs due to stomach problems.
Side Effects and Risks
The three main areas of concern with NSAIDs are the digestive system, the kidneys, and the cardiovascular system.
Stomach and Digestive Issues
Because NSAIDs block COX-1, which normally helps maintain the protective mucus lining of your stomach, regular use can lead to stomach irritation, ulcers, and gastrointestinal bleeding. This risk increases with higher doses and longer use. Taking NSAIDs with food or using a COX-2 selective NSAID like celecoxib can help reduce this risk, though it doesn’t eliminate it entirely. Problems can occur in both the upper and lower digestive tract.
Kidney Effects
Prostaglandins help regulate blood flow to your kidneys, so blocking their production can strain kidney function. For most people taking an occasional ibuprofen, this isn’t a concern. But for anyone with existing kidney problems, or for people using NSAIDs regularly at high doses, the risk of kidney damage increases.
Heart Attack and Stroke Risk
The FDA has strengthened its warning that non-aspirin NSAIDs can increase the risk of heart attack and stroke. This risk can appear as early as the first few weeks of use, increases with higher doses and longer duration, and applies to people both with and without existing heart disease. People who already have heart disease or risk factors for it face a greater likelihood of these events. There is also an increased risk of heart failure with NSAID use. The FDA’s guidance is straightforward: use the lowest effective dose for the shortest time necessary.
Who Should Avoid NSAIDs
Certain groups face elevated risks. The FDA warns against using NSAIDs at 20 weeks of pregnancy or later because they can cause kidney problems in the developing baby, leading to dangerously low amniotic fluid levels. After 30 weeks, NSAIDs also risk causing premature closure of a key blood vessel in the fetus. Low-dose aspirin (81 mg) is an exception and may actually be recommended for certain pregnancy-related conditions under medical guidance.
Children and teenagers should not take aspirin when they have the flu or chickenpox due to the risk of Reye’s syndrome, a rare but serious condition that affects the brain and liver. Aspirin can appear under other names on labels, including acetylsalicylic acid and salicylate, and it shows up in some unexpected products like Alka-Seltzer. Other NSAIDs like ibuprofen are generally considered safe for children at appropriate doses.
People with chronic kidney disease, a history of stomach ulcers or GI bleeding, or uncontrolled high blood pressure typically need to avoid NSAIDs or use them only under close supervision. The same applies to anyone taking blood thinners, since NSAIDs can amplify bleeding risk.
Using NSAIDs Safely
For occasional use at standard doses, NSAIDs are safe for most adults. The key principles are simple: take the smallest dose that controls your symptoms, don’t use them for longer than necessary, and avoid combining multiple NSAIDs (taking ibuprofen and naproxen together, for example, doubles the side effect risk without adding much benefit). Prescription-strength naproxen, for reference, has a maximum daily dose of 1,650 mg for arthritis and should not exceed 1,375 mg daily for acute headache or migraine.
If you find yourself reaching for an NSAID most days for weeks at a time, that’s worth a conversation with your doctor. Not because the occasional pill is dangerous, but because long-term daily use shifts the risk profile meaningfully, and there may be better strategies for managing whatever’s causing your pain.