Ibuprofen is short acting, while naproxen is long acting and more likely to cause an upset stomach.

Naproxen and ibuprofen are both NSAIDs so they are similar in many ways, but there are important differences.

Effectiveness of Naproxen and Ibuprofen

Naproxen and ibuprofen are called nonselective NSAIDs because they block COX-2 enzymes (involved in pain signalling and inflammation) and also COX-1 enzymes (associated with a protective effect on stomach lining). This makes them effective at relieving pain and reducing inflammation, but there is a risk of stomach-related side effects. As far as effectiveness goes, a dose of 440mg naproxen is approximately equivalent to a dose of 400mg ibuprofen.

Naproxen is Long Acting and Ibuprofen is Short Acting

One of the most important differences is the length of time they act for. Ibuprofen is considered a short-acting NSAID, with a relatively quick onset of action. It is better suited for the treatment of acute pain and is the most appropriate NSAID for children. Ibuprofen tablets or capsules (such as Advil, Motrin) need to be given every four to six hours. Naproxen is considered long-acting, and can be given twice daily. It has a slower onset of effect and is better suited for the treatment of chronic conditions.

Naproxen is More Likely to Cause Gastrointestinal Side Effects Because it is Long Acting

Research has discovered that the risk of gastrointestinal (GI) side effects such as stomach ulcers and stomach bleeding increases the longer somebody takes NSAIDS. Naproxen is more likely than ibuprofen to cause GI side effects because it is longer acting. To reduce the risk of GI side effects, NSAIDS should only be taken at their lowest effective dose, for the shortest possible time. Doubling up on NSAIDs (for example taking naproxen and ibuprofen at the same time) is unnecessary, and to be avoided as it increases the risk of both GI and cardiovascular side effects. If you are prescribed low-dose aspirin to reduce your risk of a heart attack or stroke, then talk to your doctor BEFORE taking NSAIDs, as these may negate the protective effects of aspirin.

NSAIDs Increase the Risk Of Cardiovascular Side Effects

Another worrying side effect of some NSAIDs is an increased risk of cardiovascular events such as a heart attack. Research has identified that those NSAIDs that have more of a tendency to block COX-2 compared to COX-1 have an increased risk of thrombosis (blood clotting). Naproxen (at dosages up to 1000mg per day) does not appear to be associated with an increased risk of detrimental vascular events, and experts tend to prefer naproxen for this reason. Low-dose ibuprofen (dosages up to 1200mg per day) is considered an alternative to naproxen; however, higher dosages of ibuprofen (up to the recommended maximum of 2400mg/day) are associated with a higher risk of cardiovascular events. People who have already had a heart attack or stroke must use NSAIDs with caution. One study showed that even one or two doses of ibuprofen or diclofenac (another NSAID) increased the risk of another event. During the 14 weeks of the study, naproxen did not appear to increase this risk. However, NSAIDS should not be used after coronary artery bypass graft (CABG) surgery and all NSAIDS carry a warning that they can increase the risk of cardiovascular events, so should only be used under a doctor's supervision, particularly in people with a history of heart disease. Reassuringly, the risk of a cardiovascular event such as a heart attack, stroke, or death is extremely small when NSAIDs are prescribed for short periods of time - such as for a musculoskeletal injury - in people at low cardiovascular risk.

Other Side Effects Common to all NSAIDs

All NSAIDs have been associated with kidney toxicity and allergic-type reactions. NSAIDs also interact with other medications including angiotensin converting enzyme (ACE) inhibitors, angiotensin-II receptor blockers (ARBs), diuretics, clopidogrel, warfarin, dabigatran, and aspirin.

In summary

Naproxen (in dosages up to 1000mg/day) or low-dose ibuprofen (in dosages up to 1200mg/day) are preferred if NSAIDs are deemed necessary in adults. At these dosages, risk of cardiovascular events in people with no pre-existing risk factors is low, although risk of GI side-effects may be higher with naproxen.

Important Guidance

When taking any NSAID, the following guidance is given:

• Acetaminophen is preferred over NSAIDs, when appropriate
• If a NSAID is deemed necessary, take only the lowest possible dose for the shortest possible time
• Naproxen (in dosages up to 1000mg/day) and ibuprofen (in dosages up to 1200mg/day) are the preferred NSAIDs. Ibuprofen is the most appropriate NSAID for children
• Avoid using long-acting formulations of NSAIDs as these have a higher risk of GI side effects
• Do not take any other NSAID-containing products while being treated with a NSAID
• Doctors should review the need for continued NSAID administration at each consultation
• In people with pre-existing heart disease or who have suffered a heart attack or stroke, NSAIDS should only be used with caution and only under a doctor's supervision
• Older patients, patients with type 2 diabetes or with a history of stomach ulcers, kidney problems or at risk for heart disease are more likely to suffer from NSAID-related complications such as GI side effects, cardiovascular events, and kidney toxicity. NSAIDS should be avoided, but if deemed necessary, their usage should be monitored by a doctor.