GI ulcers and bleeding are the most common NSAID side effects.

Outline at a glance

• What NSAIDs do in simple terms

• The big takeaway: GI ulcers and/or bleeding are the most common side effects

• Why the gut bears the highest burden

• Other possible, less common effects

• How clinicians minimize risk and what owners can watch for

• Practical takeaways you can use in real-world care

NSAIDs in veterinary care: a quick, friendly refresher

Pain is an everyday part of animal life—whether a dog with arthritis that slows their strolls or a cat recovering from an injury. Non-steroidal anti-inflammatory drugs, or NSAIDs, are a trusted line of defense because they quiet inflammation and ease pain. But they’re not a blunt instrument. Here’s the thing: they work by dampening certain enzymes—cyclooxygenase enzymes, or COX for short—that help generate prostaglandins. Prostaglandins are chemical messengers that tell blood vessels to widen, nerves to amplify pain signals, and, yes, the gut to protect itself with a mucus shield.

If you’ve ever watched a pet doctor explain, you’ll hear a delicate balance described: curb the pain and inflammation without compromising the animal’s gut and kidneys. Some NSAIDs are more selective for the COX-2 enzyme, which is more involved in inflammation. Others hit COX-1 a bit more, and COX-1 is the one that helps keep the stomach lining nicely coated with protective mucus. The compromise is real, and that’s exactly where the risk comes in.

The standout side effect: why GI issues steal the spotlight

The single most common side effect tied to NSAID use is gastrointestinal ulceration and/or bleeding. Let’s break down why that happens, so you can recognize the pattern quickly.

• Gut protection relies on prostaglandins: When NSAIDs block COX enzymes, the production of prostaglandins drops. Prostaglandins help produce the protective mucus layer that coats the stomach and small intestines. Without that shield, stomach acid and digested food can irritate sensitive tissue.

• Acid plus fewer safeguards equals trouble: With less mucus, the stomach lining becomes more vulnerable. Ulcers can form, and in the worst cases, bleeding can occur. It’s not just about pain—it's about real, visible signs like vomiting, a drop in appetite, or darker stools.

• It isn’t all-or-nothing: The risk isn’t identical for every animal. Dose matters, as does how long the animal has been on the medication. Pre-existing GI conditions, dehydration, age, and concurrent illnesses can tilt the risk upward.

• It can affect more than the gut: While the gut is the most common casualty, NSAIDs can also influence blood clotting and kidney function, especially if the animal is volume-depleted or has other health concerns. Still, compared with GI issues, those effects are less frequent.

A quick tour of other potential, though less common, side effects

You’ll hear about a few other possibilities, even if they don’t pop up as often as GI upset:

• Kidney concerns: NSAIDs can reduce blood flow to the kidneys, which may stress renal function—particularly in dehydrated pets, those with existing kidney issues, or animals on long courses of NSAIDs.

• Respiratory reactions: Some animals may show breathing difficulties or other airway reactions, though this is rare.

• Skin and soft tissue responses: Rashes or other mild skin changes can occur, but they’re not as typical as gut-related problems.

• Interactions and contraindications: NSAIDs don’t always play nicely with every other drug. For example, combining NSAIDs with certain steroids or other NSAIDs can raise risks. It’s a classic reminder to review the full medication list before starting a new drug.

How clinicians reduce risk and keep an eye on things

Quality care means thoughtful planning. Here are practical steps commonly used to minimize GI risk while preserving the pain control these drugs provide:

• Choose the right NSAID for the patient: Some drugs are more COX-2 selective, which can reduce GI irritation. Examples often discussed in practice include meloxicam or firocoxib, among others. The choice depends on the animal’s species, health history, and the specific condition being treated.

• Start with appropriate dosing and schedule: The minimum effective dose for the shortest duration is the guiding principle. The plan should be revisited regularly to see if a shorter course or a dose adjustment is possible.

• Give with food or a prescribed gastroprotectant when needed: Giving NSAIDs with meals can help buffer the stomach. In animals with higher GI risk, veterinarians might add a protective medication such as sucralfate, famotidine, or misoprostol to reduce ulcer risk.

• Hydration and kidney monitoring: Ensure the animal is well-hydrated, and monitor kidney function with blood tests when NSAIDs are used long-term or if dehydration is a factor. Regular rechecks help catch subtle changes early.

• Screen for GI disease and drug interactions: A history of ulcers, vomiting, diarrhea, or blood in stool raises flags. Vet teams also review all other medications to avoid risky combinations.

• Individualize the approach: Not every dog or cat tolerates a specific NSAID the same way. If one drug isn’t tolerated, a clinician may switch to another with a different COX selectivity profile or consider alternative pain relief strategies.

What to watch for at home

If you’re caring for a pet on NSAIDs, stay attuned to how they’re feeling day to day. Early signals can save the gut from bigger trouble down the road:

• Signs of GI distress: vomiting, decreased appetite, weight loss, or black, tarry stools can hint at GI irritation or ulcers.

• Behavioral cues: Lethargy, discomfort when touching the abdomen, or restlessness after meals may point to abdominal issues.

• Hydration and urine output: If a pet drinks less, urinates less, or seems lethargic, it could reflect dehydration or kidney stress.

• Bleeding or bruising: Unusual nosebleeds, prolonged bleeding from a minor cut, or reddish urine deserve prompt attention.

What this means when you’re in the clinic or at home

Here’s the practical takeaway: NSAIDs are powerful allies for alleviating pain and inflammation, but they’re not innocuous. The key is to balance benefits with risks, especially GI risk. A thoughtful approach—selecting the right NSAID, dosing wisely, protecting the gut when needed, and keeping a close eye on the animal’s overall health—lets you harness the good stuff while limiting the drawbacks.

A few real-world touches that make a difference

• In real clinics, you’ll hear about COX-2 selective options that aim to reduce GI irritation while still delivering anti-inflammatory relief. These choices aren’t a one-size-fits-all—they depend on the animal’s species, temperament, and medical history.

• Owners often appreciate concrete guidelines: give with meals, watch for signs of GI upset in the first week, and keep a simple medication calendar to avoid accidental double-dosing.

• For long-term conditions, a plan might include periodic reevaluation of the drug choice and dose, plus a proactive GI protection strategy if GI risk is high.

A gentle note about broader pain management

NSAIDs aren’t the only tool in the toolbox. In some cases, veterinarians blend different strategies to reduce reliance on NSAIDs alone. This can include physical therapy, nutritional adjustments to support joint health, supplemental therapies, or other classes of pain relievers when GI risk is a concern. The aim is a well-rounded, compassionate approach that keeps the animal comfortable without inviting trouble down the line.

To sum it up in a friendly line

When NSAIDs are used thoughtfully, they’re a relief you can rely on. The most common side effect—GI ulcers and/or bleeding—happens because the same mechanism that quiets inflammation also thins the gut’s protective shield. But with careful drug choice, smart dosing, gut protection when needed, and vigilant monitoring, you can hold onto the good while steering clear of the bad.

If you’re juggling this topic for real-life care, a quick mental checklist can help:

• Is the animal a good candidate for a COX-2 selective NSAID?

• Have we started with the lowest effective dose and a clear plan for reassessment?

• Do we know the animal’s GI and kidney history, and are we watching for signs of trouble?

• Is there a plan for GI protection if risk is elevated?

A final thought

Pain management in veterinary medicine often feels like walking a tightrope—balance, vigilance, and a dash of empathy. By understanding why GI ulcers and bleeding are the most common side effects, you’re better prepared to protect pets while still giving them the comfort they deserve. And that makes a real difference in daily care—for them, and for the people who love them.