PK 5 Vet

Do not use in cats at doses intended for dogs.

Carprofen is an NSAID. Like other drugs in this class, carprofen has analgesic and anti-inflammatory effects by inhibiting the synthesis of PGs. The enzyme inhibited by an NSAID is the cyclo-oxygenase (COX) enzyme. The COX enzyme exists in two isoforms, COX-1 and COX-2. COX-1 is primarily responsible for synthesis of PGs important for maintaining a healthy GI tract, renal function, platelet function, and other normal functions. COX-2 is induced and responsible for synthesizing PGs that are important mediators of pain, inflammation, and fever. (There may be crossover of COX-1 and COX-2 effects in some situations.) Carprofen is relatively COX-1 sparing compared with older NSAIDs, but it is not considered a COX-2– selective agent. It is not known if the specificity for COX-1 or COX-2 determines efficacy or safety. In some studies, carprofen was not a strong inhibitor of peripheral PG synthesis, and because of its high lipophilicity, its effects may be mediated by effects in the central nervous system (CNS).

ACE INHIBITORS (e.g., benazepril, enalapril): Because ACE inhibitors potentially can reduce renal blood flow, use with NSAIDs could increase the risk for renal injury. However, one study in dogs receiving tepoxalin did not show any adverse effect. It is unknown what effects, if any, occur if other NSAIDs and ACE inhibitors are used together in dogs.
ASPIRIN: When aspirin is used concurrently with carprofen, plasma levels of carprofen could decrease and an increased likelihood of GI adverse effects (blood loss) could occur. Concomitant administration of aspirin with carprofen cannot be recommended. Washout periods of several days is probably warranted when switching from an NSAID to aspirin therapy in dogs.
CORTICOSTEROIDS: Concomitant administration with NSAIDs may significantly increase the risks for GI adverse effects
DIGOXIN: Carprofen may increase serum levels of digoxin; use with caution in patients with severe cardiac failure
FUROSEMIDE: Carprofen may reduce the saluretic and diuretic effects of furosemide
HIGHLY PROTEIN BOUND DRUGS (e.g., phenytoin, valproic acid, oral anticoagulants, other antiinflammatory agents, salicylates, sulfonamides, sulfonylurea antidiabetic agents): Because carprofen is highly bound to plasma proteins (99%), it potentially could displace other highly bound drugs; increased serum levels and duration of actions may occur. Although these interactions are usually of little concern clinically, use together with caution.
METHOTREXATE: Serious toxicity has occurred when NSAIDs have been used concomitantly with methotrexate; use together with extreme caution
PHENOBARBITAL, RIFAMPIN, or OTHER HEPATIC ENZYME INDUCING AGENTS: As carprofen hepatotoxicity may be mediated by its hepatic metabolites, these drugs should be avoided if carprofen is required. One source states: Patients should not receive phenobarbital or other hepatic drug metabolizing enzyme inducers when receiving this drug (Boothe 2005).
PROBENECID: May cause a significant increase in serum levels and halflife of carprofen

The safety of carprofen in dogs was determined by the sponsor during preclinical studies. The most common adverse effect in dogs has been in the GI tract (vomiting, anorexia, and diarrhea). GI ulcers, perforation, and bleeding are uncommon in dogs but possible. In rare cases, carprofen has caused idiosyncratic acute hepatic toxicity in dogs. Signs of toxicity usually appear 2–3 weeks after exposure. There were no adverse effects on the kidneys when carprofen was evaluated in anesthetized dogs. Carprofen may lower total thyroid (T4) concentrations in dogs but not free T4. In experimental dogs, it has inhibited bone healing in some models (4.4 mg/kg/day × 120 days), but this has not been shown to be a clinical problem. 

Carprofen has produced toxicity in cats if administered at the same dose rates as for dogs.

The manufacturer states that the safe use of carprofen in dogs less than 6 weeks of age, pregnant dogs, dogs used for breeding purposes, or lactating bitches has not been established. Carprofen has been given to pregnant rats at dosages of up to 20 mg/kg during day 7–15 of gestation. While no teratogenic effects were noted in pups, the drug did delay parturition with an increased number of dead pups at birth

Do not administer to animals prone to GI ulcers. Do not administer with ulcerogenic drugs such as corticosteroids. If a patient has had previous adverse effects from NSAIDs, carprofen should be used cautiously.

Injection should be stored at 2-8 degree C.