NSAIDs in Dogs and Cats: Safe Prescribing Guide
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Narration for: NSAIDs in Dogs and Cats: Safe Prescribing Guide
~40 min read · Clinically structured · Updated for practice & exams
COX-1/COX-2 selectivity, washout periods, renal and GI risk stratification, species-specific dose tables, firocoxib/meloxicam/carprofen comparison, and monitoring protocols — the complete guide to safe NSAID prescribing in dogs and cats.
Key takeaways
- COX-2 selective NSAIDs (firocoxib, robenacoxib, mavacoxib) have a wider GI safety margin than non-selective NSAIDs (carprofen, meloxicam), but NO NSAID is completely safe — all can cause GI ulceration, renal injury, and hepatotoxicity.
- Cats eliminate NSAIDs slowly due to deficient glucuronidation — feline NSAID use requires reduced doses, longer dosing intervals, and strict limits on treatment duration.
- A 5–7 day washout period is mandatory when switching between NSAIDs, and between NSAIDs and corticosteroids. There is no safe overlap.
- Baseline renal function (BUN, creatinine, USG) should be documented before initiating long-term NSAID therapy in any patient — and rechecked within 7–14 days of starting, then every 3–6 months.
- NSAID-induced hepatotoxicity is idiosyncratic and unpredictable — carprofen is the most commonly implicated NSAID in dogs. Any dog on carprofen that becomes anorexic, icteric, or lethargic should have liver enzymes and bile acids checked immediately.
Red flags / do not miss
- NSAID + CORTICOSTEROID = NEVER. Washout of 5–7 days mandatory between them. GI perforation mortality ~50%.
- Do NOT use two different NSAIDs concurrently or sequentially without a washout — additive COX-1 inhibition and GI toxicity with no additional analgesic benefit.
- Ibuprofen, naproxen, diclofenac, and piroxicam are HUMAN NSAIDs — their safety in dogs and cats has NOT been established. Do not prescribe these off-label. Ibuprofen causes severe GI ulceration at doses as low as 25 mg/kg in dogs.
- Carprofen hepatotoxicity is the most common NSAID-related cause of acute hepatic failure in dogs — it is idiosyncratic, can occur at any time during therapy (days to months), and requires immediate drug discontinuation and supportive care.
- NSAIDs should be discontinued 48–72 hours before general anaesthesia (if elective) to allow renal autoregulation to recover. In an emergency, ensure the patient is volume-loaded before induction to protect renal perfusion.
1. Introduction: The NSAID Dilemma
Non-steroidal anti-inflammatory drugs are the most commonly prescribed analgesics in small-animal practice, and simultaneously the drug class responsible for the highest number of serious adverse drug reactions reported to veterinary pharmacovigilance databases. In a 2020 UK study, NSAIDs accounted for 25% of all adverse drug reaction reports in dogs, with GI ulceration, renal injury, and hepatotoxicity being the most frequent serious events.
This guide provides a comprehensive, evidence-based framework for safe NSAID prescribing. It covers the molecular pharmacology of COX-1 and COX-2 inhibition, a head-to-head comparison of the most commonly used veterinary NSAIDs, risk-stratification tools for GI and renal toxicity, species-specific dosing tables, washout protocols, and monitoring recommendations.
2. COX-1 and COX-2: The Molecular Basis of NSAID Effects and Toxicity
| Parameter | COX-1 (Constitutive) | COX-2 (Inducible) | COX-2 (Constitutive — Kidney, CNS) |
|---|---|---|---|
| Expression | Constitutively expressed in most tissues | Induced by inflammation, cytokines, growth factors | Constitutively expressed in the kidney (macula densa, medullary interstitium) and CNS |
| Physiological role | Gastric mucosal protection (prostaglandin-mediated mucus and bicarbonate secretion, mucosal blood flow), platelet aggregation (thromboxane A2), renal perfusion (afferent arteriole vasodilation in volume-depleted states) | Mediates inflammation: vasodilation, sensitisation of nociceptors to bradykinin and histamine, pyrexia (hypothalamic PGE2) | Renal: maintenance of GFR in volume-depleted states, renin secretion, sodium and water excretion. CNS: pain processing, synaptic plasticity. |
| Effect of NSAID inhibition | GI ulceration, platelet dysfunction, renal hypoperfusion (in volume-depleted patients) | Analgesia, anti-inflammatory effect, antipyresis | Renal injury in volume-depleted patients (even with COX-2 selective NSAIDs) |
2.1 The COX-1/COX-2 Selectivity Ratio
NSAID selectivity is expressed as the COX-1/COX-2 IC50 ratio — the concentration required to inhibit each isoenzyme by 50%. A ratio > 1 indicates COX-2 selectivity; < 1 indicates COX-1 selectivity. However, these ratios are species-specific and assay-dependent. The table below provides approximate rankings based on canine whole-blood assays:
| NSAID | COX-1/COX-2 IC50 Ratio (Canine) | Selectivity Classification | Key Clinical Implication |
|---|---|---|---|
| Firocoxib (Previcox) | > 350 | Highly COX-2 selective (coxib) | Widest GI safety margin. Minimal platelet effect. |
| Robenacoxib (Onsior) | ~140 | Highly COX-2 selective (coxib) | Excellent GI safety. Licensed for short-term use in cats. |
| Mavacoxib (Trocoxil) | > 100 | Highly COX-2 selective (coxib) | Long-acting (monthly dosing). Not for acute pain. |
| Deracoxib (Deramaxx) | ~12–30 | COX-2 preferential | Good GI safety. Approved for postoperative and chronic pain. |
| Carprofen (Rimadyl) | ~1.8–8 | COX-2 preferential (weak) | Moderate GI safety. Most commonly implicated in hepatotoxicity. |
| Meloxicam (Metacam) | ~2–10 | COX-2 preferential | Moderate GI safety. Licensed for cats (single-dose or short course). |
| Ketoprofen | ~0.5–1 | Non-selective (COX-1 and COX-2) | Narrow safety margin. Higher GI and renal risk. |
| Aspirin | < 0.1 | Highly COX-1 selective (at low doses) | Irreversible COX-1 acetylation. 7–10 day platelet effect. Do not combine with other NSAIDs. |
2.2 The 'COX-2-Safe Renal' Myth
A common misconception is that COX-2 selective NSAIDs do not cause renal injury. This is FALSE. The kidney constitutively expresses COX-2 in the macula densa and medullary interstitium, where it plays a critical role in maintaining GFR during volume depletion. COX-2 selective NSAIDs CAN and DO cause renal injury — particularly in dehydrated, hypotensive, or geriatric patients. The protective advantage of COX-2 selectivity is primarily GI, not renal.
3. Species-Specific NSAID Prescribing
3.1 Canine NSAID Doses
| NSAID | Dose (Dog) | Route | Frequency | Indications | Key Precautions |
|---|---|---|---|---|---|
| Carprofen | 4.4 mg/kg (or 2.2 mg/kg q12h) | SC, IV, PO | q24h (or divided q12h) | Osteoarthritis, postoperative pain, acute inflammation | Hepatotoxicity — idiosyncratic, unpredictable. Monitor ALT at baseline, 2 weeks, then q3–6 months. |
| Meloxicam | 0.2 mg/kg IV/SC once (loading), then 0.1 mg/kg PO q24h | SC, IV, PO | q24h | Osteoarthritis, postoperative pain | Liquid formulation for small dogs allows accurate dosing. Oral suspension is well-tolerated. |
| Firocoxib | 5 mg/kg PO q24h | PO | q24h | Osteoarthritis (FDA-approved). Also used for postoperative pain. | COX-2 selective — wider GI safety margin. Chewable tablet is palatable to most dogs. |
| Robenacoxib | 2 mg/kg PO (or 1–2 mg/kg SC) | SC, PO | q24h | Postoperative pain, acute musculoskeletal pain | Rapid onset (30 min). Short half-life — suitable for acute, not chronic, use. |
| Deracoxib | 1–2 mg/kg PO (chronic OA); 3–4 mg/kg PO (postoperative — limit to 7 days) | PO | q24h | Osteoarthritis, postoperative pain | Higher postoperative dose has increased GI risk — limit course to ≤ 7 days. |
| Mavacoxib | 2 mg/kg PO, repeat in 14 days, then monthly | PO | Monthly (after loading) | Osteoarthritis — chronic therapy only. Not for acute pain. | Long-acting. Cannot be rapidly withdrawn if adverse effects occur. Contraindicated in dogs with any history of NSAID sensitivity. |
| Grapiprant (Galliprant) | 2 mg/kg PO q24h | PO | q24h | Osteoarthritis (FDA-approved) | NOT an NSAID — it is an EP4 prostaglandin receptor antagonist. Different mechanism, but similar monitoring recommendations. |
3.2 Feline NSAID Doses
CATS ARE NOT SMALL DOGS. Feline NSAID use is constrained by deficient glucuronidation and a narrow therapeutic index. The following table is conservative — many practitioners use lower doses or avoid NSAIDs in cats altogether, particularly for chronic conditions.
| NSAID | Dose (Cat) | Route | Frequency | Maximum Duration | Key Precautions |
|---|---|---|---|---|---|
| Meloxicam | 0.3 mg/kg SC once (perioperative). Then 0.05 mg/kg PO q24h if continued. | SC (single), PO | q24h (reduced dose) | 4–5 days (off-label chronic use longer) | The only NSAID widely used for chronic feline OA. Must be given with food. Monitor renal function before and 1 week after starting. |
| Robenacoxib | 1–2 mg/kg SC/PO | SC, PO | q24h | 3 days (licensed). Off-label up to 6 days for acute pain. | Licensed for feline postoperative pain. COX-2 selective — better safety margin than meloxicam in cats. |
| Carprofen | 2–4 mg/kg SC/IV once (perioperative) | SC, IV | ONCE (single dose) | Single dose only — do NOT repeat. | Carprofen elimination is very slow in cats. Repeated dosing causes accumulation and toxicity. Single-dose perioperative use only. |
| Ketoprofen | 1–2 mg/kg SC once | SC | ONCE (single dose) | Single dose only. | Narrow safety margin. Not recommended for routine use. |
Critical feline rule
Never administer more than one dose of carprofen to a cat. The elimination half-life is prolonged (9–20+ hours vs 8 hours in dogs), and repeated dosing leads to drug accumulation and toxicity. If ongoing analgesia is required after a single perioperative carprofen dose, switch to an opioid (buprenorphine).
4. GI and Renal Risk Stratification
4.1 GI Ulceration Risk Factors
Before prescribing an NSAID, assess the patient's individual risk of GI adverse effects:
| Risk Factor | Risk Level | Recommendation |
|---|---|---|
| No risk factors — young, healthy dog, acute pain, short course (≤ 7 days) | LOW | Any licensed NSAID at standard dose. Recheck if GI signs develop. |
| Age > 7 years | MODERATE | Prefer COX-2 selective NSAID (firocoxib). Baseline renal panel. Recheck within 14 days. |
| History of GI signs with previous NSAID | HIGH | Use grapiprant (EP4 antagonist — not an NSAID), or add misoprostol (2–5 μg/kg PO q8h) to the NSAID. Strongly consider alternative analgesia (gabapentin, amantadine, acupuncture). |
| Concurrent corticosteroid therapy | CONTRAINDICATED | Never co-administer. 5–7 day washout required. |
| Concurrent other NSAID or aspirin | CONTRAINDICATED | Never co-administer. Washout between NSAIDs. |
| Known GI disease (IBD, previous GI ulcer, GI neoplasia) | HIGH | Avoid NSAIDs. Use opioids, gabapentin, or paracetamol (dogs only — 10–15 mg/kg PO q8–12h) for analgesia. |
| Concurrent high-dose prednisolone (tapered and stopped within the washout period) | MODERATE | Washout as above. Once started, monitor closely for GI signs for the first 14 days. |
4.2 Renal Injury Risk Factors
- Dehydration (any cause): Correct volume deficit before administering NSAID. Dehydrated patients are dependent on renal prostaglandins to maintain GFR.
- Hypotension (anaesthesia, shock, haemorrhage): Do not administer an NSAID until the patient is normotensive and volume-replete.
- Pre-existing renal disease: NSAIDs are relatively contraindicated. If necessary, use the lowest dose, monitor renal function at baseline and q48–72h, and ensure the patient is never volume-depleted. Grapiprant may be a safer alternative (different mechanism).
- Concurrent nephrotoxic drugs: Aminoglycosides, amphotericin B, cisplatin, and ACE inhibitors (in volume-depleted patients) increase the risk of NSAID-induced renal injury. Avoid or use with extreme caution.
- Age > 10 years: Age-related decline in GFR is common. Baseline renal panel mandatory. Recheck within 7 days of starting NSAID therapy.
5. Washout Protocols and Drug Switching
Washout periods allow clearance of the initial NSAID and restoration of normal COX activity before a new NSAID (or corticosteroid) is introduced.
| Switch From | Switch To | Minimum Washout | Alternative Analgesia During Washout |
|---|---|---|---|
| NSAID A | NSAID B | 5–7 days | Opioids (buprenorphine, methadone, tramadol — with CYP caution), gabapentin, paracetamol (dogs only) |
| NSAID | Corticosteroid | 5–7 days | Opioids, gabapentin, paracetamol (dogs only) |
| Corticosteroid | NSAID | 5–7 days | Opioids, gabapentin, paracetamol (dogs only). Note: HPA suppression may persist — ensure patient is not Addisonian. |
| Aspirin | Any NSAID | 7–10 days | Aspirin's effect on platelets lasts the lifespan of the platelet (7–10 days). Do not administer another NSAID until platelet COX-1 has been replenished. |
6. Monitoring Protocols
6.1 Baseline (Before Starting NSAID Therapy)
- CBC (including platelet count)
- Serum biochemistry: BUN, creatinine, ALT, ALP, GGT, total protein, albumin
- Urinalysis including urine specific gravity
6.2 Short Course (≤ 7 Days)
- Owner monitoring: appetite, vomiting, diarrhoea, melena, lethargy. Instruct owner to stop NSAID and contact clinic if any of these develop.
- No routine laboratory monitoring required for healthy young dogs receiving a short course.
6.3 Long-Term Therapy (> 7 Days)
- 2 weeks after starting: Recheck biochemistry (BUN, creatinine, ALT, ALP). If ALT or ALP have increased > 2× baseline, discontinue NSAID and investigate hepatotoxicity.
- Every 3–6 months: Biochemistry, urinalysis. Owner-reported quality-of-life and pain scores.
- Annually: Full CBC, biochemistry, urinalysis. Consider bile acids if ALT is persistently elevated.
6.4 Signs to Instruct the Owner to Report Immediately
- Complete anorexia (not just reduced appetite — the dog stops eating entirely)
- Vomiting (especially with blood or coffee-ground material)
- Melena (black, tarry stool)
- Lethargy or depression
- Jaundice (yellow gums, sclera, or skin)
- Increased water consumption and urination (may indicate renal injury)
7. Head-to-Head Comparison and Clinical Selection Algorithm
| Clinical Scenario | First Choice | Rationale | Alternative |
|---|---|---|---|
| Acute postoperative pain (healthy, young dog) | Carprofen 4.4 mg/kg SC once, then PO q24h for 3–7 days, OR robenacoxib 2 mg/kg SC once, then PO q24h | Both are rapid-onset, effective for acute pain, and well-tolerated for short courses. | Meloxicam (single SC loading dose followed by oral maintenance) |
| Chronic osteoarthritis (geriatric dog, no comorbidities) | Firocoxib 5 mg/kg PO q24h, OR grapiprant 2 mg/kg PO q24h | COX-2 selectivity provides wider GI safety for long-term use. Grapiprant (non-NSAID) is an alternative for dogs with previous NSAID intolerance. | Carprofen or meloxicam if cost is a factor. Meloxicam oral suspension allows precise dosing in small dogs. |
| Chronic OA (dog with history of NSAID GI intolerance) | Grapiprant 2 mg/kg PO q24h, OR NSAID + misoprostol 2–5 μg/kg PO q8h | Grapiprant bypasses COX inhibition entirely (EP4 receptor antagonist). Misoprostol replaces the prostaglandin-mediated GI protection lost to NSAID use. | Gabapentin + amantadine (non-NSAID multimodal analgesia) |
| Chronic OA (dog with CKD Stage 1–2) | Grapiprant (no COX inhibition), OR firocoxib at the LOWEST dose with q2-week renal monitoring | Grapiprant does not inhibit renal COX-2. If an NSAID must be used, firocoxib's COX-2 selectivity provides the best renal safety margin among NSAIDs. | Opioid + gabapentin multimodal analgesia (avoid NSAIDs entirely for Stage 3–4 CKD) |
| Feline perioperative pain (OVH, dental) | Meloxicam 0.3 mg/kg SC once at induction, OR robenacoxib 2 mg/kg SC once | Single-dose meloxicam is well-studied in cats and provides 24-hour analgesia. Robenacoxib is COX-2 selective with a good feline safety profile. | Buprenorphine 0.02 mg/kg IM q6–8h (opioid — no NSAID renal risk) |
| Feline chronic OA | Meloxicam 0.05 mg/kg PO q24h (off-label chronic use), with food, for a limited course | The only NSAID with significant clinical experience for chronic feline OA. Use the lowest effective dose. Monitor renal function q1–3 months. | Gabapentin 5–10 mg/kg PO q8–12h (non-NSAID). Consider solensia (frunevetmab — anti-NGF monoclonal antibody, feline-licensed). |
Clinical pearls
- Greyhounds have a higher volume of distribution and slower clearance for many NSAIDs — use the lowest effective dose and consider therapeutic drug monitoring where available.
- Fasted administration of NSAIDs does NOT significantly reduce GI ulceration risk — the protective effect of food is minimal against COX-1-mediated prostaglandin inhibition. If GI protection is needed, use misoprostol (a synthetic prostaglandin E1 analogue), not an acid suppressant.
- A platelet count is advisable before NSAID therapy — NSAIDs reversibly inhibit platelet COX-1, reducing thromboxane A2 production. This is clinically relevant primarily in patients with pre-existing thrombocytopenia or coagulopathy.
- The COX-2 selectivity of an NSAID is species-dependent — celecoxib is highly COX-2 selective in humans but is non-selective in dogs and should NOT be used off-label in veterinary patients.
- NSAID-induced renal injury is almost always pre-renal and reversible if caught early. The triad of risk factors: dehydration, hypotension, and concurrent nephrotoxic drugs (aminoglycosides, ACE inhibitors in volume-depleted patients).
Frequently asked questions
How long does it take for a dog's GI tract to recover from an NSAID-induced ulcer?
Mucosal recovery begins within 24 hours of NSAID discontinuation, but full restoration of the protective mucus-bicarbonate barrier takes 3–7 days. This is one reason for the 5–7 day washout between NSAIDs. If an ulcer has already formed (penetrating beyond the mucosa), healing takes 2–4 weeks and requires discontinuation of NSAIDs plus treatment with sucralfate and, if indicated, a proton-pump inhibitor.
Can I give a dog an NSAID and paracetamol together?
Paracetamol (acetaminophen) is NOT an NSAID — it has negligible COX-inhibitory activity. It can be co-administered with an NSAID in dogs for multimodal analgesia. The canine paracetamol dose is 10–15 mg/kg PO q8–12h, not to exceed 45 mg/kg/day. This combination is contraindicated in cats.
Is meloxicam safer than carprofen for long-term use in dogs?
Both have similar safety profiles in large clinical trials. Carprofen has a slightly higher reported incidence of hepatotoxicity (idiosyncratic). Meloxicam has a slightly higher reported incidence of GI adverse effects in some studies. Neither is clearly 'safer' — the choice depends on the individual patient's risk factors, previous NSAID tolerance, and the clinician's experience.
Why does carprofen cause hepatotoxicity in some dogs?
Carprofen hepatotoxicity is idiosyncratic — it is NOT dose-dependent and is NOT predictable. The mechanism is believed to involve the formation of reactive acyl glucuronide metabolites that covalently bind to hepatic proteins, triggering an immune-mediated hepatocellular injury in susceptible dogs. It can occur at any time (days to months into therapy). Labrador Retrievers appear over-represented, suggesting a possible genetic predisposition.
What is the safest NSAID for a cat with chronic kidney disease?
No NSAID is completely safe in a cat with CKD. Meloxicam at the lowest dose (0.02–0.05 mg/kg PO q24h — below the standard feline dose) has been used in some studies of cats with stable CKD and OA, with monitoring at 1 week, 1 month, and q3 months thereafter. However, the risk of precipitating acute-on-chronic renal injury is real. Grapiprant is not licensed for cats. Gabapentin and solensia (frunevetmab) are safer non-NSAID alternatives for feline chronic OA.
How important is the 'no NSAID for 48 hours before anaesthesia' rule?
This rule is a precaution to allow renal autoregulation to recover before the hypotensive insult of general anaesthesia. In an otherwise healthy, well-hydrated dog undergoing elective surgery, the risk of a single perioperative NSAID dose causing renal injury is extremely low. The rule is more important for geriatric patients, those with pre-existing renal disease, or those undergoing procedures with expected significant haemorrhage or hypotension. Balance analgesic needs against renal risk — withholding an NSAID in a painful patient is also harmful.
Should I give an NSAID with food?
Yes — administration with a small meal reduces the incidence of minor GI upset (nausea, regurgitation) but does NOT significantly reduce the risk of GI ulceration. The ulcerogenic effect of NSAIDs is mediated by systemic COX-1 inhibition (reducing prostaglandin-mediated mucosal protection), not by direct topical irritation. Food has no effect on this systemic mechanism.
What is the clinical significance of COX-2 selectivity?
COX-2 selective NSAIDs (firocoxib, robenacoxib) spare COX-1 at therapeutic doses, which means they have minimal effects on gastric mucosal prostaglandin production and platelet thromboxane A2 synthesis. The result: a 3–5× reduction in the risk of clinically significant GI ulceration and a negligible effect on platelet function. This makes them preferred for geriatric patients and those requiring long-term therapy.
Self-check quiz
Test yourself. Answers are below each question — cover them first if you are studying.
Q1. A 9-year-old Labrador Retriever has been on carprofen 4.4 mg/kg q24h for osteoarthritis for 3 months. The owner reports the dog has been anorexic for 2 days and seems 'yellow.' Serum biochemistry reveals ALT 850 U/L, ALP 1200 U/L, and total bilirubin 4.2 mg/dL. What is the most likely diagnosis?
- Pancreatitis — discontinue carprofen and start maropitant
- Idiosyncratic carprofen hepatotoxicity — discontinue carprofen immediately and start supportive care
- Biliary obstruction — perform abdominal ultrasound
- Leptospirosis — start doxycycline
- Corticosteroid-induced hepatopathy — the owner must be giving prednisolone without telling you
Show answer
Answer: Idiosyncratic carprofen hepatotoxicity — discontinue carprofen immediately and start supportive care
Anorexia, jaundice, and markedly elevated liver enzymes in a dog on carprofen is the classic presentation of idiosyncratic carprofen hepatotoxicity. This is a medical emergency — discontinue carprofen immediately, start IV fluids, administer hepatoprotectants (S-adenosylmethionine, N-acetylcysteine, vitamin E), and provide supportive care. Most dogs recover if the drug is stopped early. A small subset progresses to fulminant hepatic failure.
Q2. Which of the following statements about COX-2 selective NSAIDs and renal function is TRUE?
- COX-2 selective NSAIDs do not affect renal function because COX-2 is not expressed in the kidney
- COX-2 selective NSAIDs can cause renal injury because COX-2 is constitutively expressed in the kidney
- COX-2 selective NSAIDs protect the kidney from injury
- Only non-selective NSAIDs cause renal injury
- Renal injury from NSAIDs is always irreversible
Show answer
Answer: COX-2 selective NSAIDs can cause renal injury because COX-2 is constitutively expressed in the kidney
COX-2 is constitutively expressed in the macula densa, medullary interstitium, and endothelial cells of the renal vasculature, where it plays a critical role in maintaining GFR, especially during volume depletion. COX-2 selective NSAIDs can cause renal injury in the same way non-selective NSAIDs can — the protective advantage of COX-2 selectivity is GI, not renal.
Q3. A 5 kg cat undergoes ovariohysterectomy and receives meloxicam 0.3 mg/kg SC at induction. The owner would like to continue analgesia at home for 3 days. What is the most appropriate oral meloxicam dose?
- Continue at 0.3 mg/kg PO q24h
- 0.1 mg/kg PO q24h for 3 days
- 0.05 mg/kg PO q24h for a maximum of 4–5 days
- 0.2 mg/kg PO q12h for 3 days
- Meloxicam cannot be used orally in cats — switch to carprofen
Show answer
Answer: 0.05 mg/kg PO q24h for a maximum of 4–5 days
Following the single perioperative feline dose (0.3 mg/kg SC), the oral maintenance dose in cats is the lower 'chronic feline dose' of 0.05 mg/kg PO q24h, given for a maximum of 4–5 days. This accounts for the cat's slow NSAID elimination. Continuing at 0.3 mg/kg orally would rapidly lead to toxic accumulation.
Q4. A 12-year-old dog with Stage 2 CKD and painful osteoarthritis requires analgesia. Which of the following is the SAFEST first-line choice?
- Carprofen 2.2 mg/kg PO q12h
- Meloxicam 0.1 mg/kg PO q24h
- Firocoxib 5 mg/kg PO q24h
- Grapiprant 2 mg/kg PO q24h
- Prednisolone 0.5 mg/kg PO q24h (anti-inflammatory dose)
Show answer
Answer: Grapiprant 2 mg/kg PO q24h
Grapiprant is an EP4 prostaglandin receptor antagonist — it is NOT a COX inhibitor. It provides analgesia without inhibiting COX-1 or COX-2, making it the safest analgesic choice for a patient with CKD where renal prostaglandin-mediated perfusion is critical. All NSAIDs carry renal risk in CKD patients. Prednisolone would cause immunosuppression and protein catabolism without adequate analgesia for OA.
Q5. An owner has been giving their dog aspirin 10 mg/kg q12h for arthritis for 2 weeks without veterinary advice. They now present the dog for a proper consultation. You want to switch the dog to firocoxib. What is the minimum washout period required?
- 24 hours — aspirin has a short half-life in dogs
- 3 days
- 5 days
- 7–10 days
- No washout needed — firocoxib and aspirin have different mechanisms
Show answer
Answer: 7–10 days
Aspirin irreversibly acetylates platelet COX-1, and the effect lasts the lifespan of the platelet (7–10 days in dogs). Starting another NSAID (which also inhibits COX-1, even if COX-2 selective) before the aspirin-affected platelets have been replaced will result in additive platelet dysfunction and GI ulceration risk. A 7–10 day washout is mandatory.
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Educational disclaimer: This article is for veterinary students and licensed professionals. It is not a substitute for case-specific clinical judgment, local formulary rules, or current drug labels. Always verify doses, legality, and species contraindications before treating.
