RIMADYL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for RIMADYL (RIMADYL).
Selective cyclooxygenase-2 (COX-2) inhibitor, reducing prostaglandin synthesis involved in inflammation, pain, and fever.
| Metabolism | Hepatic metabolism primarily via CYP2C9 and glucuronidation; excreted in urine and feces. |
| Excretion | Primarily hepatic metabolism (oxidation, conjugation) with ~70% of metabolites excreted in urine and ~30% in feces via biliary elimination. Less than 5% excreted unchanged. |
| Half-life | Terminal elimination half-life: 12–18 hours in dogs at recommended doses. Clinical context: Supports twice-daily dosing; longer half-life in some breeds may require dose adjustment. |
| Protein binding | Highly protein bound: >99% (primarily albumin). |
| Volume of Distribution | Apparent volume of distribution (Vd): ~0.3–0.5 L/kg in dogs, suggesting limited tissue distribution, primarily in plasma and extracellular fluid. |
| Bioavailability | Oral: ~80–90% (fasting state); food may reduce rate but not extent. Subcutaneous: ~100% relative to IV. Rectal: Not recommended (variable). |
| Onset of Action | Oral: 2–4 hours; Subcutaneous: 1–2 hours; Intravenous: within 1 hour. Clinical effect (analgesia/antipyretic) typically observed within 2–4 hours after oral administration. |
| Duration of Action | Analgesic effect: 12–24 hours, with peak at 3–6 hours. Clinical notes: Duration may be shorter in acute pain; once-daily dosing often sufficient for chronic conditions. |
| Molecular Weight | 352.39 |
50-100 mg orally twice daily, or 100-200 mg rectally once daily (suppository).
| Dosage form | TABLET |
| Renal impairment | Contraindicated in patients with severe renal impairment (GFR < 30 mL/min). For moderate impairment (GFR 30-59 mL/min), reduce dose by 50% and monitor renal function. |
| Liver impairment | Contraindicated in Child-Pugh class C. For class B, reduce dose by 50% and monitor liver enzymes. No adjustment needed for class A. |
| Pediatric use | Not recommended for children under 12 years; for adolescents 12-18 years, 50 mg orally twice daily. |
| Geriatric use | Start at lowest effective dose (50 mg twice daily), monitor renal function and avoid long-term use due to increased risk of GI bleeding and renal impairment. |
| 1st trimester | Not recommended; teratogenic risk in animal studies (cleft palate, skeletal malformations). Use only if benefit outweighs risk. |
| 2nd trimester | Avoid; potential for premature ductus arteriosus closure and oligohydramnios. NSAID-related fetal renal impairment. |
| 3rd trimester | Contraindicated; risk of premature ductus arteriosus closure, neonatal pulmonary hypertension, and oligohydramnios. Avoid use after 30 weeks gestation. |
Clinical note
Comprehensive clinical and safety monograph for RIMADYL (RIMADYL).
| Placental transfer | Crosses placenta; detected in fetal plasma at concentrations ~50% of maternal levels. |
| Breastfeeding | Excreted in breast milk in low concentrations. Risk of infant toxicity is low with short-term use, but avoid prolonged use due to potential neonatal adverse effects (e.g., thrombocytopenia, renal impairment). |
■ FDA Black Box Warning
No FDA boxed warning for human use; in veterinary use, repeated administration may cause hepatic or renal toxicity.
| Serious Effects |
Active peptic ulcer diseaseSevere uncontrolled hypertensionHistory of hypersensitivity to NSAIDsSevere renal impairment (eGFR <30 mL/min)Third trimester of pregnancyConcurrent use of aspirin or other NSAIDs
| Precautions | Risk of gastrointestinal ulceration and bleeding, Renal toxicity in dehydrated or hypotensive patients, Hepatic toxicity risk with chronic use, Cardiovascular thrombotic events risk |
| Food/Dietary | Administer with food to reduce gastrointestinal irritation. Avoid giving with high-fat meals as it may affect absorption. |
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| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | FDA Pregnancy Category B. No evidence of fetal harm in animal studies; no adequate human studies. Risk cannot be ruled out. Use only if clearly needed. |
| Fetal Monitoring | Monitor for NSAID-related adverse effects: GI bleeding, renal function, hepatic function, and platelet count. Ultrasound if prolonged use. |
| Fertility Effects | NSAIDs may impair fertility via inhibition of prostaglandin synthesis; reversible upon discontinuation. |
| Clinical Pearls |
| Rimadyl (carprofen) is a nonsteroidal anti-inflammatory drug (NSAID) used primarily in dogs for osteoarthritis and postoperative pain. Use with caution in patients with pre-existing renal, hepatic, or gastrointestinal disease. Administer with food to reduce GI upset. Monitor renal function and liver enzymes in long-term use. Avoid concurrent use with other NSAIDs or corticosteroids due to increased risk of GI ulceration and renal toxicity. |
| Patient Advice | Rimadyl is an NSAID used to treat arthritis pain and inflammation in dogs. · Give the medication with food to decrease the chance of stomach upset. · Watch for signs of side effects: decreased appetite, vomiting, diarrhea, dark or tarry stools, increased drinking or urination, jaundice, or lethargy. · Do not give with any other NSAIDs or steroids unless directed by your veterinarian. · Keep out of reach of children and pets. Store at room temperature. |