NSAIDs, short for nonsteroidal anti-inflammatory drugs, are a widely used class of medications that reduce pain, inflammation, and fever. You’ve almost certainly taken one: ibuprofen (Advil, Motrin) and naproxen (Aleve) are the most common over-the-counter versions, and aspirin is technically an NSAID as well. They work by blocking a specific enzyme in your body that triggers swelling, pain, and elevated temperature.
How NSAIDs Work in Your Body
When tissue is damaged or irritated, your body produces chemicals called prostaglandins. These are the direct cause of the swelling, pain, and heat you feel at an injury site or during an illness. NSAIDs block the enzyme (cyclooxygenase, or COX) responsible for making prostaglandins. Less prostaglandin production means less inflammation, less pain signaling, and a lower fever.
There are two versions of this enzyme. COX-1 is active all the time and plays a housekeeping role, particularly in protecting your stomach lining and helping with blood clotting. COX-2 ramps up specifically during inflammation. Most traditional NSAIDs block both versions, which is why they’re effective for pain but can cause stomach problems as a side effect. A newer subclass, called COX-2 selective inhibitors (celecoxib is the most common), was designed to target only the inflammation-related enzyme while sparing the stomach-protective one.
What NSAIDs Treat
NSAIDs are used for a broad range of everyday and chronic conditions:
- Headaches and dental pain
- Muscle aches and back pain
- Menstrual cramps
- Arthritis (both osteoarthritis and rheumatoid)
- Tendonitis and bursitis
- Fever from illness
For short-term pain like a headache or a pulled muscle, over-the-counter NSAIDs are often the first choice. For chronic conditions like arthritis, a prescription-strength NSAID or a COX-2 selective version may be more appropriate because of the longer duration of use.
Common Types and How They Differ
Not all NSAIDs last the same amount of time in your body, and that difference shapes how often you take them. Ibuprofen is short-acting, typically taken every six to eight hours. Naproxen lasts longer and is usually taken twice a day, which makes it a better fit for steady, all-day pain relief. Prescription options like diclofenac fall somewhere in between, dosed two to three times daily.
Aspirin is a unique case. While it’s technically an NSAID, it permanently disables the COX enzyme in platelets, the blood cells responsible for clotting. Other NSAIDs only block the enzyme temporarily. This permanent effect is why low-dose aspirin is used to prevent heart attacks and strokes in people at high risk, a role no other NSAID fills. It also means that taking ibuprofen at the same time as aspirin can actually interfere with aspirin’s heart-protective benefit, because ibuprofen can block aspirin from reaching the enzyme first.
Stomach and Digestive Risks
The most well-known side effect of NSAIDs is stomach irritation, which ranges from mild discomfort to serious ulcers and bleeding. Because these drugs block COX-1, they reduce the protective mucus layer in your stomach. The risk is higher if you are over 65, take high doses or multiple NSAIDs, have a history of ulcers, drink alcohol regularly, smoke, or take certain other medications alongside NSAIDs, particularly corticosteroids, blood thinners, or antidepressants in the SSRI class.
For people who need NSAIDs regularly but are at risk for stomach problems, doctors often prescribe a proton pump inhibitor (a common acid-reducing medication) to be taken alongside the NSAID. Taking NSAIDs with food can also help reduce stomach irritation, though it doesn’t eliminate the risk entirely.
Heart and Cardiovascular Risks
All non-aspirin NSAIDs carry an increased risk of heart attack and stroke. The FDA requires a boxed warning on every NSAID label stating this. The risk can begin within the first weeks of regular use and increases with higher doses and longer duration. People who already have heart disease face a higher absolute risk, but even those without known heart problems are not immune.
NSAIDs should not be used right before or after coronary artery bypass graft surgery. If you’ve had a recent heart attack, NSAID use may increase the chance of another one. The general guidance is to use the lowest effective dose for the shortest time possible.
Who Should Avoid NSAIDs
Certain groups face outsized risks from these medications. People with kidney disease need to be particularly careful, because NSAIDs reduce blood flow to the kidneys and can worsen function. A dangerous combination known as the “triple whammy” occurs when someone takes an NSAID together with two common types of blood pressure medication (an ACE inhibitor or ARB plus a diuretic), which can cause significant kidney damage.
Pregnant women should avoid NSAIDs from 20 weeks of pregnancy onward. After that point, these drugs can impair the baby’s kidney function, leading to dangerously low amniotic fluid levels. After 30 weeks, NSAIDs pose an additional risk by potentially causing premature closure of a blood vessel in the baby’s heart. The one exception is low-dose aspirin (81 mg), which is sometimes prescribed during pregnancy for specific conditions like preeclampsia prevention.
People with aspirin-sensitive asthma can experience severe breathing reactions to any NSAID, not just aspirin. If you’ve ever had wheezing, nasal polyps, or a respiratory flare after taking aspirin, all NSAIDs in this class are best avoided.
Interactions With Other Medications
NSAIDs interact with several common drug classes. Blood thinners (anticoagulants) combined with NSAIDs significantly increase the risk of bleeding, since both affect clotting through different pathways. Blood pressure medications, including ACE inhibitors, ARBs, beta blockers, and calcium channel blockers, can become less effective when you’re also taking an NSAID, because NSAIDs promote fluid retention and raise blood pressure. The kidney risk from the “triple whammy” combination of an ACE inhibitor or ARB, a diuretic, and an NSAID is well documented and worth knowing about if you take blood pressure medication.
Even over-the-counter use matters here. If you regularly take low-dose aspirin for heart protection, adding ibuprofen or naproxen for pain can blunt aspirin’s antiplatelet effect. Timing matters: if you need both, taking aspirin at least 30 minutes before ibuprofen can help preserve its benefit.