Naproxen
Naproxen is an NSAID used much less often in animals than in people. Its prolonged elimination in dogs creates a substantial toxicity risk.
Group
Nonsteroidal anti-inflammatory drug
Mechanism of Action
Inhibits cyclooxygenase and decreases prostaglandin synthesis.
Dose Rates
Horses
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Musculoskeletal pain | 10 mg/kg | PO | Every 12 h | Up to 14 days; Historical veterinary regimen; use requires gastrointestinal and renal risk assessment. |
| Alternative musculoskeletal pain regimen | 10 mg/kg | PO | Every 24 h | |
| Historical parenteral loading before oral therapy — Loading | 5 mg/kg | IV | Once | Slow IV using the former equine injection; follow the separately prescribed oral course. The old injectable product is no longer described as marketed. |
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Historical musculoskeletal pain regimen | Reference only | PO | Historical regimen: 5 mg/kg initially, then 2 mg/kg every 48 hours. Published guidance states use is not recommended in dogs because prolonged elimination increases serious toxicity risk. |
Rabbits
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Septic arthritis pain or inflammation | Reference only | PO | Up to 21 days; 2.4 mg/mL in drinking water for 21 days was described. Water intake and systemic exposure vary; this is a drinking-water concentration, not a body-weight prescription. |
Indications
- Selected equine musculoskeletal pain
- Historical canine treatment, now not recommended
Contraindications
- Patients with gastrointestinal ulceration or bleeding
- Dehydration or significant renal compromise
Interactions
- Do not combine with other NSAIDs or corticosteroids.
- May interfere with diuretics and ACE inhibitors.
- Probenecid can increase naproxen exposure and half-life.
- Anticoagulants increase bleeding risk; aminoglycosides increase renal risk.
- Methotrexate toxicity may be increased; bisphosphonates add GI injury risk.
Adverse effects
- Gastrointestinal ulceration or hemorrhage
- Renal injury
Toxicity
Dogs eliminate naproxen slowly and can develop severe toxicity after human OTC exposure. Treat overdose as a prolonged gastrointestinal and renal risk.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Naproxen tablets 250 mg | Tablet | 250 mg / tablet | PO |
| Naproxen tablets 375 mg | Tablet | 375 mg / tablet | PO |
| Naproxen tablets 500 mg | Tablet | 500 mg / tablet | PO |
| Naproxen oral suspension 25 mg/mL | Oral Liquid | 25 mg / mL | PO |
Monitoring and Administration
Assess hydration, renal function and gastrointestinal signs. Monitor for vomiting, melena and appetite loss.
Do not equate naproxen sodium tablet mass with naproxen mass: 220 mg naproxen sodium corresponds to 200 mg naproxen. Human tablet doses must not be extrapolated to dogs.
Canine exposures above 5 mg/kg can cause GI signs or ulcers; significant renal injury has occurred from about 10–25 mg/kg and neurologic signs above 50 mg/kg. These are toxicity observations, not safe boundaries.
Significant overdose requires gastrointestinal and renal assessment, tailored decontamination when appropriate, gastroprotection and fluid/electrolyte management. Continued GI monitoring/support may be needed for 10–14 days.