NSAID stands for nonsteroidal anti-inflammatory drug. It’s a class of widely used 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. They’re among the most commonly used medications in the world, and understanding how they work helps you use them safely.
How NSAIDs Work in Your Body
When your body is injured or infected, it produces chemicals called prostaglandins that trigger inflammation, pain, and fever. NSAIDs work by blocking the enzymes (called COX-1 and COX-2) that your cells need to make prostaglandins. By cutting off prostaglandin production at the source, NSAIDs reduce swelling, relieve pain, and bring down fevers.
The “nonsteroidal” part of the name exists to distinguish these drugs from corticosteroids like prednisone, which also reduce inflammation but through a completely different mechanism and with a different set of side effects. NSAIDs are not steroids.
Common Over-the-Counter and Prescription NSAIDs
The NSAIDs you can buy without a prescription include:
- Ibuprofen (Advil, Motrin)
- Naproxen sodium (Aleve)
- Aspirin (Bayer)
Several stronger NSAIDs require a prescription:
- Celecoxib (Celebrex), a selective type that targets only COX-2
- Diclofenac (Voltaren), available as pills or a topical gel
- Indomethacin (Indocin)
- Ketorolac (Toradol), often used for short-term severe pain
All of these work through the same basic mechanism. The prescription versions tend to be stronger or more targeted, but they share the same core benefits and risks.
What NSAIDs Are Used For
NSAIDs are effective for a broad range of everyday pain and inflammatory conditions. Their primary benefit, based on clinical trials, is reducing the severity of musculoskeletal pain, stiffness, and swelling. That makes them a go-to choice for headaches, menstrual cramps, muscle strains, arthritis, tendinitis, and minor injuries. They also lower fevers caused by illness.
For chronic conditions like rheumatoid arthritis and osteoarthritis, NSAIDs can be part of a longer-term management plan, though the risks increase with extended use.
Selective vs. Non-Selective NSAIDs
Your body has two versions of the enzyme NSAIDs block. COX-1 handles everyday housekeeping tasks like protecting your stomach lining and supporting kidney function. COX-2 ramps up mainly when tissue is damaged and drives the inflammatory response. Most common NSAIDs, like ibuprofen and naproxen, block both versions. These are called non-selective NSAIDs.
Selective NSAIDs, like celecoxib, target primarily COX-2. The idea is to reduce inflammation without disrupting COX-1’s protective work in the stomach, which can mean fewer gastrointestinal side effects. However, selectively blocking COX-2 creates its own problems. It can interfere with blood vessel function in ways that may increase the risk of blood clots. In clinical trials, the rate of serious adverse events, including hospitalization and life-threatening complications, was actually higher with COX-2 selective NSAIDs than with non-selective ones. Neither type is clearly “safer” overall; they simply shift the risk profile.
Stomach and Digestive Risks
The most well-known side effect of NSAIDs is stomach trouble. This ranges from mild nausea and heartburn to serious complications like stomach ulcers and gastrointestinal bleeding. The reason ties directly to how these drugs work: the same prostaglandins that cause pain and inflammation also help maintain a protective mucus layer in your stomach. When NSAIDs suppress prostaglandin production, that protective barrier weakens.
But prostaglandin loss alone doesn’t fully explain stomach damage. NSAIDs also increase stomach muscle contractions, which disrupts blood flow to the stomach lining. This creates small areas of reduced circulation that become vulnerable to injury. Over time, or at higher doses, this can progress to ulcers. Taking NSAIDs with food or using the lowest effective dose for the shortest time helps reduce this risk.
Heart and Cardiovascular Risks
NSAIDs carry an FDA boxed warning, the most serious type, stating they may increase the risk of heart attack and stroke. This risk rises with longer use and is higher in people who already have heart disease or risk factors for it. NSAIDs should never be used right before or after coronary artery bypass surgery.
The cardiovascular risk comes partly from the way NSAIDs affect blood pressure. By blocking prostaglandins in the kidneys, NSAIDs can cause your body to retain more salt and water, raising blood pressure by an average of about 5 mmHg. That may sound small, but for someone already managing high blood pressure or heart failure, it can be significant.
Effects on Kidney Function
Your kidneys rely on prostaglandins to help regulate blood flow, especially when your body is under stress from dehydration, blood loss, or existing kidney problems. NSAIDs can reduce blood flow to the kidneys and impair their ability to filter waste. In most healthy, well-hydrated people, this isn’t a major concern with occasional use. But in people who are dehydrated, elderly, or already have reduced kidney function, NSAIDs can trigger acute kidney injury. The good news is that this type of kidney damage is typically reversible once you stop taking the drug.
Aspirin and Children
Aspirin is the one NSAID with a unique and serious restriction for young people. Giving aspirin to children or teenagers who have the flu or chickenpox has been linked to Reye’s syndrome, a rare but potentially fatal condition that causes swelling in the liver and brain. Children and teens should not take aspirin unless specifically directed by a physician for a condition like Kawasaki disease that requires it. Ibuprofen and acetaminophen (which is not an NSAID) are safer alternatives for fever and pain in young people.
Drug Interactions to Know About
NSAIDs interact with several commonly prescribed medications. They can reduce the effectiveness of blood pressure medications by promoting salt and water retention. If you take blood thinners, NSAIDs increase bleeding risk. They can also slow the clearance of lithium (used for bipolar disorder) from your body, potentially raising lithium to harmful levels. For people on methotrexate, a medication used for autoimmune conditions and certain cancers, NSAIDs can increase methotrexate concentrations in the blood by interfering with how it’s processed.
Combining NSAIDs with certain diuretics, particularly potassium-sparing types, has been associated with kidney problems and dangerously high potassium levels. If you take any prescription medications regularly, it’s worth checking whether NSAIDs are safe to add into the mix.
How to Use NSAIDs More Safely
For over-the-counter naproxen, the typical maximum for pain relief is 1,000 mg per day, while prescription doses for conditions like rheumatoid arthritis can go up to 1,500 mg per day. The general principle for all NSAIDs is to use the lowest dose that controls your symptoms, for the shortest period necessary. Taking them with food can help buffer stomach irritation, though it doesn’t eliminate the risk entirely.
People with a history of stomach ulcers, heart disease, kidney problems, or asthma triggered by aspirin should be particularly cautious. If you’ve ever had hives or an allergic reaction to one NSAID, you may react to others in the same class as well.