Yes, Alka-Seltzer Original contains an NSAID. Each tablet includes 325 mg of aspirin, which is a nonsteroidal anti-inflammatory drug. The product’s own label identifies it this way and carries the standard NSAID stomach-bleeding warning. This matters because many people reach for Alka-Seltzer thinking of it purely as an antacid, without realizing they’re also taking a pain reliever that carries real risks.
What’s Actually in the Tablet
Alka-Seltzer Original is a combination product with three active ingredients: aspirin (325 mg), sodium bicarbonate, and citric acid. When you drop the tablet into water, the sodium bicarbonate and citric acid react to create the fizz. Once dissolved, the liquid you drink contains sodium citrate (which acts as the antacid) and a dissolved form of aspirin (sodium acetylsalicylate, which is the NSAID pain reliever).
A standard dose is two tablets, meaning you’re taking 650 mg of aspirin in one go. That’s equivalent to two regular aspirin tablets. If you’re using Alka-Seltzer for an upset stomach and didn’t realize it contained aspirin, you could easily double up if you also take a separate aspirin or another NSAID like ibuprofen.
How It Works as an NSAID
Aspirin reduces pain, fever, and inflammation by blocking enzymes that produce prostaglandins, chemical messengers your body releases in response to injury. One form of these enzymes handles everyday maintenance tasks like protecting your stomach lining and supporting blood clotting. The other ramps up when you’re hurt or inflamed. Aspirin blocks both, which is why it relieves pain and swelling but can also irritate the stomach and thin the blood.
The effervescent format does change how the aspirin gets into your system. A crossover study comparing a single 325 mg dose found that aspirin dissolved in a sodium bicarbonate-citrate buffer (the Alka-Seltzer formula) was absorbed significantly faster than an unbuffered aspirin tablet. The speed difference comes down to how quickly the solution leaves your stomach. However, about 25% more intact aspirin reaches the bloodstream from a standard tablet, because the buffered solution gets absorbed mostly through the intestine, where some aspirin breaks down before entering circulation. The total amount of pain-relieving salicylate absorbed ends up being equivalent either way.
Stomach Bleeding Risk
The FDA has issued a specific warning about aspirin-containing antacid products like Alka-Seltzer. The concern is that people treating heartburn or indigestion may not realize they’re taking an NSAID repeatedly, increasing their risk of gastrointestinal bleeding. This risk is higher if you:
- Are 60 or older
- Have a history of stomach ulcers or bleeding problems
- Take blood thinners (anticoagulants)
- Take steroid medications like prednisone
- Take other NSAIDs such as ibuprofen or naproxen
- Drink three or more alcoholic drinks daily
The irony is worth noting: many people take Alka-Seltzer specifically because their stomach hurts. But the aspirin inside can actually make stomach problems worse over time, particularly with frequent use.
Interactions With Other NSAIDs
If you take low-dose aspirin daily for heart protection, combining it with ibuprofen can actually block aspirin’s blood-thinning benefit. The FDA notes that ibuprofen at 400 mg interferes with aspirin’s ability to prevent clots when the two are taken together. If you need both, taking ibuprofen at least 30 minutes after your aspirin, or at least 8 hours before it, can help avoid the interference. Naproxen may cause a similar problem, though the timing window appears narrower. Acetaminophen (Tylenol) does not interfere with aspirin’s clot-preventing effects.
This interaction works both directions. If you’ve already taken Alka-Seltzer (and its 325 mg of aspirin per tablet), adding ibuprofen on top means you’re stacking two NSAIDs, which compounds the stomach bleeding risk without necessarily improving pain relief.
Not All Alka-Seltzer Products Contain Aspirin
The Alka-Seltzer brand spans a wide product line, and not every version contains aspirin. Alka-Seltzer Original, Extra Strength, and some cold and flu formulas include it. But products marketed specifically for heartburn relief may use only antacid ingredients without aspirin. The only reliable way to know is to check the “Active Ingredients” box on the package. If aspirin is present, the label will list it by name and identify it as an NSAID.
Who Should Avoid It
Because Alka-Seltzer Original contains aspirin, it should not be given to children or teenagers, especially those recovering from the flu or chickenpox. Aspirin use in this age group is linked to Reye’s syndrome, a rare but serious condition that causes swelling in the liver and brain. The only exception is children on long-term aspirin therapy for specific conditions like Kawasaki disease, prescribed by a doctor.
The sodium bicarbonate in each tablet also adds a significant amount of sodium to each dose. If you’re on a sodium-restricted diet for high blood pressure or heart or kidney issues, this is worth factoring in, especially at the two-tablet dose.