Drugs and medications image
Drugs and medications image EquiMed


nah-PROX-en - Pronunciation guide

Brand Names

  • Aleve
  • Anaprox
  • E C Naprosyn
  • Equiproxen 10% Solution
  • Equiproxen Granules


Rx symbolNaproxen is perhaps the most effective nonsteroidal anti-inflammatory drug (NSAID) for the treatment of muscle pain and soft tissue injury in horses.  In some cases, it is not as effective in treating joint injuries. Naproxen does not speed healing or cure the underlying problem, but will make the horse more comfortable while recovering. Naproxen is absorbed promptly, but full clinical response may not occur for several days.


Naproxen is used to treat lameness, musculoskeletal pain from soft tissue injury, muscle soreness, and bone and joint problems.

Dosage and Administration

Prescription medicationNaproxen
Method Dosage
(click row for calculator)
Concentration Period Duration
Intravenous injection 5 mg/kg 100 mg/ml Single loading dose injection1 NA
Oral (granules) 10 mg/kg 8000 mg/packet Twice daily NA
Oral (tablets) 10 mg/kg 250 mg/tablet Twice daily NA
Oral (tablets) 10 mg/kg 375 mg/tablet Twice daily NA
Oral (tablets) 10 mg/kg 500 mg/tablet Twice daily NA


  • Federal law restricts this drug to use by or on the order of a licensed veterinarian.
  • Extra-label use of drugs in treating animals is allowable only by licensed veterinarians within the context of a valid veterinarian-client-patient relationship, and does not include drug use in treating animals by the layman (except under the supervision of a licensed veterinarian).
  • 1Recommended to follow injectible form with oral form for continued treatment.
  • The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your equine appears to feel better, the entire treatment plan should be completed to prevent relapse.
  • This medication may be available in forms and concentrations not noted in the above table. Always check the label and literature provided with the medication about the form and concentration and DO NOT USE the calculator if the information differs.
  • Calculator is for educational purposes only. Follow your veterinarian's instructions regarding use of this, or any medication.

Side Effects

Adverse reactions are uncommon in horses.  Gastrointestinal problems, such as ulcers, diarrhea, and GI pain may occur in some horses. Rare side effects include kidney damage, bleeding disorders, and protein loss.


Naproxen should be avoided or very carefully monitored in horses with liver disease, kidney disease, or gastrointestinal problems.

Naproxen was once sold as a veterinary product under the brand name Equiproxen. It is now available only as a human product.  It is a prescription drug restricted to use by or on the lawful written or oral order of a licensed veterinarian.

Naproxen is a regulated or prohibited substance in most sanctioned competitions. It is important to check with the individual regulatory group.


Naproxen should not be combined with other anti-inflammatory drugs that tend to cause GI ulcers, such as corticosteroids and other NSAIDs.  It should not be combined with anticoagulant drugs, such as warfarin, and other coumarin derivatives or sulfa antibiotics.

Naproxen may decrease the diuretic activity of furosemide.


Overdose of naproxen causes severe manifestations of the side effects and the animal will show early signs of toxicity, including loss of appetite, colic, and depression.


Naproxen Cosequin ASU TabletsNaproxen Cosequin ASU Tablets


About the Author

EquiMed Staff

EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.