NSAID stands for nonsteroidal anti-inflammatory drug. It’s a class of medications that reduce pain, fever, and inflammation, and it includes some of the most commonly used drugs in the world: ibuprofen (Advil, Motrin), naproxen (Aleve), and aspirin. You can buy many NSAIDs over the counter, though stronger versions require a prescription.
The “nonsteroidal” part of the name simply means these drugs are not steroids. Steroids like prednisone also fight inflammation, but they work through a completely different mechanism and carry a different set of side effects. NSAIDs were named to distinguish them from that older class of anti-inflammatory drugs.
How NSAIDs Work in Your Body
When tissue in your body is damaged or irritated, it produces chemicals called prostaglandins. Prostaglandins trigger inflammation, amplify pain signals, and raise your body temperature. NSAIDs work by blocking the enzymes (called COX enzymes) that your body needs to make prostaglandins. Less prostaglandin production means less swelling, less pain, and lower fever.
Your body has two main versions of this enzyme. One version is active all the time and helps maintain your stomach lining, support kidney function, and regulate blood flow. The other version ramps up mainly during injury or illness and drives inflammation. Most common NSAIDs, like ibuprofen and naproxen, block both versions. That’s why they’re effective at reducing pain but can also cause stomach problems as a side effect. Some prescription NSAIDs are designed to target only the inflammation-related enzyme, which can be easier on the stomach.
What NSAIDs Are Used For
NSAIDs treat a wide range of everyday problems:
- Pain relief: headaches, toothaches, muscle strains, sprains, and post-surgical pain
- Fever reduction: bringing down a high temperature from illness
- Inflammation: period cramps, arthritis, tendinitis, and some autoimmune conditions
This is one key difference between NSAIDs and acetaminophen (Tylenol). Both reduce pain and fever, but only NSAIDs reduce inflammation. If you have a swollen, inflamed joint or a muscle injury with visible swelling, an NSAID will address the inflammation directly in a way that acetaminophen cannot.
Common Examples
Over-the-counter NSAIDs include ibuprofen (sold as Advil or Motrin), naproxen (Aleve), and aspirin. These are available at virtually any pharmacy or grocery store. Prescription-strength NSAIDs include higher doses of these same drugs, plus others like celecoxib (Celebrex), which is designed to be more selective in targeting inflammation while reducing stomach-related side effects.
How Aspirin Differs From Other NSAIDs
Aspirin is technically an NSAID, but it behaves differently in one important way. While other NSAIDs temporarily block the COX enzyme, aspirin permanently disables it. This irreversible action is what makes aspirin uniquely useful as a blood thinner. Platelets, the tiny blood cells responsible for clotting, rely on that enzyme. Once aspirin knocks it out, those platelets can’t promote clotting for the rest of their lifespan (about 7 to 10 days). That’s why low-dose aspirin is widely used to prevent heart attacks and strokes in people at risk for cardiovascular disease, a role that other NSAIDs don’t fill.
Side Effects and Risks
The most common side effect of NSAIDs is stomach irritation. Because these drugs block the enzyme that helps maintain your stomach’s protective lining, regular use can lead to erosions, ulcers, and in serious cases, bleeding in the digestive tract. This risk increases the longer you take them and at higher doses. Taking NSAIDs with food or using the lowest effective dose for the shortest time helps reduce this risk.
NSAIDs can also affect your kidneys. The same prostaglandins that drive inflammation also help regulate blood flow to the kidneys, so blocking them can reduce kidney function, particularly in people who already have kidney problems or are dehydrated. Non-aspirin NSAIDs also carry a cardiovascular risk. The FDA warns that these drugs can increase the chance of heart attack or stroke, even in people without prior heart disease, though the risk is higher with long-term use.
Who Should Be Cautious
NSAIDs are not safe for everyone. People with a history of stomach ulcers, kidney disease, or heart disease need to be especially careful. If you have asthma, NSAIDs can sometimes trigger a flare, particularly aspirin.
Pregnancy is another important consideration. The FDA recommends avoiding NSAIDs from 20 weeks of pregnancy onward because they can cause kidney problems in the developing baby, leading to dangerously low levels of amniotic fluid. After 30 weeks, the risk increases further because NSAIDs can cause premature closure of a blood vessel in the baby’s heart that needs to stay open until birth. The one exception is low-dose aspirin (81 mg), which is sometimes prescribed during pregnancy for specific conditions.
For short-term, occasional use in otherwise healthy adults, NSAIDs are generally safe and effective. The risks climb with prolonged daily use, higher doses, and in people who have underlying health conditions that make them more vulnerable to these effects.