An NSAID, or nonsteroidal anti-inflammatory drug, is a class of medication that reduces pain, fever, and inflammation. You’ve almost certainly used one: ibuprofen (Advil, Motrin), naproxen (Aleve), and aspirin are all NSAIDs available without a prescription. They’re among the most widely used medications in the world, effective for everything from headaches and menstrual cramps to arthritis and muscle injuries.
The “nonsteroidal” part of the name distinguishes them from corticosteroids, which also reduce inflammation but work through a completely different mechanism and carry a different set of side effects.
How NSAIDs Work in Your Body
When tissue in your body is damaged or irritated, it produces chemical messengers called prostaglandins. These prostaglandins trigger inflammation, amplify pain signals, and raise your body temperature. NSAIDs block the enzymes (called COX-1 and COX-2) responsible for producing prostaglandins. With fewer prostaglandins circulating, you get less swelling, less pain, and lower fever.
This is also why NSAIDs cause side effects. Prostaglandins aren’t just involved in pain. They also protect your stomach lining, support kidney function, and help regulate blood clotting. Blocking them broadly means you lose some of those protective effects too, which explains the stomach and kidney issues some people experience.
Common Over-the-Counter NSAIDs
Three NSAIDs are widely available without a prescription:
- Ibuprofen (Advil, Motrin): fast-acting, typically taken every 4 to 6 hours
- Naproxen sodium (Aleve): longer-lasting, often taken every 8 to 12 hours
- Aspirin (Bayer): also used in low doses for heart protection due to its blood-thinning effect
Several stronger NSAIDs require a prescription, including celecoxib (Celebrex), diclofenac (Voltaren in prescription strength), indomethacin, and ketorolac. Celecoxib is notable because it selectively targets COX-2, which was designed to reduce stomach-related side effects compared to older NSAIDs.
NSAIDs vs. Acetaminophen
Acetaminophen (Tylenol) is often grouped with NSAIDs in people’s minds, but it’s a fundamentally different drug. Acetaminophen relieves pain and reduces fever, but it does not reduce inflammation. That distinction matters. For conditions driven by inflammation, like a sprained ankle, arthritis flare, or tendinitis, NSAIDs will typically work better because they address the underlying swelling.
On the other hand, acetaminophen is easier on the stomach and doesn’t carry the same cardiovascular or kidney risks. Its main danger is liver toxicity at high doses, particularly if you drink alcohol regularly. The recommended ceiling is generally 3,000 milligrams per day to stay safe, and it’s important to check whether other medications you take (cold remedies, prescription painkillers) already contain acetaminophen.
For moderate pain, taking acetaminophen alongside an NSAID can provide relief with lower doses of each, reducing the risk of side effects from either one. Alternating between the two is another common strategy.
Side Effects to Watch For
The most common side effect of NSAIDs is stomach irritation. Because these drugs reduce the prostaglandins that protect your stomach lining, regular use can cause discomfort, nausea, and in more serious cases, ulcers or internal bleeding. Taking NSAIDs with food helps, and your doctor may recommend a stomach acid inhibitor if you need to take them regularly.
Cardiovascular risk is another concern. The FDA strengthened its warnings in 2015 after a comprehensive safety review, stating that the risk of heart attack or stroke can occur as early as the first weeks of NSAID use and increases with higher doses and longer duration. This risk applies to people with or without pre-existing heart disease. Aspirin is the exception here: low-dose aspirin is actually used to reduce heart attack risk because of its blood-thinning properties.
Kidney problems can also develop, especially in people who are dehydrated, older, or already have reduced kidney function. NSAIDs reduce blood flow to the kidneys, and prolonged use at high doses can lead to lasting damage.
Topical NSAIDs: A Lower-Risk Option
NSAIDs also come in gel and cream forms that you apply directly to the skin over a painful joint or muscle. Diclofenac gel is the most common example. These topical versions deliver the drug locally, with only about 5% reaching your bloodstream compared to an oral pill. That dramatically reduces the risk of stomach and cardiovascular side effects.
One study found that switching from oral to topical NSAIDs reduced severe gastrointestinal problems from 26% to 17%. The tradeoff is that topical versions work best for superficial joints (knees, hands, elbows) and aren’t as effective for deeper pain or widespread inflammation. The most common side effects are mild: dry skin and itching at the application site.
Who Should Avoid NSAIDs
NSAIDs are not safe for everyone. Pregnancy is a significant concern. They are contraindicated during the third trimester because they can cause premature closure of a critical blood vessel in the fetus. Some guidelines also advise against use in the first trimester due to a possible increased risk of miscarriage and heart defects.
Aspirin specifically should not be given to children or teenagers recovering from viral infections like the flu or chickenpox. This combination has been linked to Reye syndrome, a rare but serious condition that causes swelling in the liver and brain. The Surgeon General, CDC, and American Academy of Pediatrics all advise against it. Ibuprofen and naproxen do not carry this same risk and are considered appropriate for children at age-appropriate doses.
People with a history of stomach ulcers, kidney disease, or heart failure should be cautious with any NSAID. Those who take blood thinners need to be especially careful with aspirin and other NSAIDs because of the added bleeding risk. Some people with asthma experience worsened symptoms from NSAIDs, a reaction sometimes called aspirin-exacerbated respiratory disease.
Using NSAIDs Safely
For occasional use, like a headache or sore muscles after exercise, NSAIDs are effective and well-tolerated for most adults. The key principles are straightforward: use the lowest dose that works, for the shortest time needed. Over-the-counter doses are already set at lower thresholds than prescription strength, but exceeding the label recommendations increases your risk without necessarily improving pain relief.
If you find yourself reaching for ibuprofen or naproxen daily for more than a week or two, that’s worth discussing with a healthcare provider. Chronic pain often benefits from a different approach, whether that’s a topical NSAID, physical therapy, or a treatment that targets the specific cause rather than masking symptoms with a broad anti-inflammatory.