Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used in veterinary medicine. They are used in pain control and in anti-inflammatory and antipyretic therapies. Some NSAIDs, e.g piroxicam, also have a documented anticancer effect. The objective of this study was to evaluate which of the commonly used NSAIDs (etodolac, flunixin, tolfenamic acid, carprofen, and ketoprofen) are cytotoxic to the D-17 cell line of canine osteosarcoma. The viability of the cells was evaluated using the MTT assay. Four independent repetitions were performed and the results are given as the average of these values; EC₅₀ values (half maximal effective concentration) were also calculated. The analysis of results showed that carprofen and tolfenamic acid displayed the highest cytotoxicity. Other drugs either did not provide such effects or they were very poor. For carprofen, it was possible to determine an EC₅₀ which fell within the limits of concentrations obtainable in canine serum after the administration of routinely used doses. The results are promising but further studies should be conducted to confirm them, since this study is only preliminary. The possibility of introducing carprofen and tolfenamic acid into the routine treatment of osteosarcoma in dogs should be considered.

OBJECTIVE To evaluate IM injection of oxytetracycline as an experimental model to induce pain and assess the analgesic efficacy of flunixin meglumine (FM) in dairy cows. ANIMALS 15 healthy nonlactating Jersey (n = 10) and Holstein (5) cows. PROCEDURES In the first of 2 experiments, 5 Jerseys were administered oxytetracycline (10 mg/kg, IM), divided between the right side of the neck and left hind limb. The left side of the neck and right hind limb received sham injections. Cows were also randomly assigned to receive FM (2.2 mg/kg, IV; n = 3) or an equal volume of saline (0.9% NaCl) solution (0.044 mL/kg, IV; control; 2) once daily for 5 days. The mechanical nociceptive threshold (MNT) was measured before oxytetracycline administration and at predetermined times after each injection of the assigned treatment. Experiment 2 was similar to experiment 1 except it involved 5 Jerseys and 5 Holsteins, oxytetracycline was injected only in a hind limb, and the assigned treatment was administered for 10 days. RESULTS For both experiments, mean MNT for the oxytetracycline injection site was consistently less than that for the sham injection site in the hind limbs, and mean MNT at the hind limb oxytetracycline injection site for FM-treated cows was greater than that for control cows beginning on day 3. CONCLUSIONS AND CLINICAL RELEVANCE IM injection of oxytetracycline in a hind limb reliably induced signs of pain in dairy cows and, with validation, might be useful as an experimental model for assessing pain mitigation strategies in cattle.

OBJECTIVE To describe plasma pharmacokinetic parameters and tissue elimination of flunixin in veal calves. ANIMALS 20 unweaned Holstein calves between 3 and 6 weeks old. PROCEDURES Each calf received flunixin (2.2 mg/kg, IV, q 24 h) for 3 days. Blood samples were collected from all calves before the first dose and at predetermined times after the first and last doses. Beginning 24 hours after injection of the last dose, 4 calves were euthanized each day for 5 days. Plasma and tissue samples were analyzed by ultraperformance liquid chromatography. Pharmacokinetic parameters were calculated by compartmental and noncompartmental methods. RESULTS Mean ± SD plasma flunixin elimination half-life, residence time, and clearance were 1.32 ± 0.94 hours, 12.54 ± 10.96 hours, and 64.6 ± 40.7 mL/h/kg, respectively. Mean hepatic and muscle flunixin concentrations decreased to below FDA-established tolerance limits (0.125 and 0.025 μg/mL, respectively) for adult cattle by 3 and 2 days, respectively, after injection of the last dose of flunixin. Detectable flunixin concentrations were present in both the liver and muscle for at least 5 days after injection of the last dose. CONCLUSIONS AND CLINICAL RELEVANCE The labeled slaughter withdrawal interval for flunixin in adult cattle is 4 days. Because administration of flunixin to veal calves represents extralabel drug use, any detectable flunixin concentrations in edible tissues are considered a violation. Results indicated that a slaughter withdrawal interval of several weeks may be necessary to ensure that violative tissue residues of flunixin are not detected in veal calves treated with that drug.

The pharmacokinetic aspects of tulathromycin (2.5 mg/kg b.w.) were studied following intravenous administration alone and in combination with flunixin meglumine (2.2 mg/kg b.w) in apparently healthy goats. Tulathromycin concentrations in serum were determined by microbiological assay technique using Bacillus subtiles (ATCC 66343) as test organism. The half-lives of distribution and elimination (t0.5(a)and to.5(p)) were 0.071, 0.046 and 6.43, and 5.05 h. following intravenous injection of tulathromycin alone and in combination with flunixin, respectively. Volume of distribution at steady state (Vdss) was 0.249 and 0.96l/kg., mean residence time (MRT) was 6.27 and 5.99 h and total body clearance (ClB) was 0.046 and 0.17 l/kg/hr., respectively. It was concluded that flunixin significantly altered the pharmacokinetics of tulathromycin by increase its distribution and accelerate its elimination from body. Therefore care should be taken during use of tulathromycin in goats concurrently with flunixin.

Saline (0.9% NaCl) solution, flunixin meglumine (1.1 mg/kg), prednisolone sodium succinate (1.1 mg/kg), U74389F (1.5 mg/kg), and dimethyl sulfoxide (0.5 g/kg) were each administered IV to 5 neonatal calves 15 minutes after the start of a 3-hour infusion of Escherichia coli lipopolysaccharide (LPS; 2 micrograms/kg/ hr). Four additional calves were given a 3-hour IV infusion of saline solution alone. Only flunixin significantly suppressed eicosanoid production and mitigated clinical signs associated with endotoxemia. Prednisolone provided partial protection against LPS-induced hypotension and lacticemia. Pronounced hypoglycemia and lacticemia were observed in U74389F-treated calves; LPS-induced hypotension and hypoglycemia were marked in dimethyl sulfoxide-treated calves.

Age and species reportedly affect the pharmacokinetic variables of nonsteroidal anti-inflammatory drugs. We determined the effect of age on flunixin pharmacokinetic variables in foals during the first month of life. We also estimated the physiologic activity of the drug in neonatal foals by determining the effect of flunixin on thromboxane production during clotting of blood taken from the foals. Flunixin disposition and clearance were determined after IV administration of 1.1 mg of drug/kg of body weight to 5 healthy foals when they were 24 to 28 hours, 10 to 11 days, and 27 to 28 days old. The area under the curve (2,471 micrograms.min/ml), mean residence time (477 minutes), and zero-time intercept of the elimination phase (4,853 ng/ml) were significantly (P = 0.05) greater, the elimination half-life (339 minutes) and slope of the elimination phase (0.002 L/min) were significantly (P = 0.05) longer, and total body clearance (0.482 ml/min/kg) and zero-time intercept for the distribution phase (2,092 ng/ml) were significantly (P = 0.05) lower at 24 to 28 hours. At each age, a biexponential equation was best fitted to the plasma flunixin concentration from each foal. Thromboxane B2 production during clotting of blood was significantly (P = 0.05) suppressed for 12 hours after flunixin meglumine administration at all ages. Therefore, it appears that although age does alter the disposition and elimination of flunixin in neonatal foals, this effect may be of little consequence because the drug's physiologic activity in foals appears similar to that in mature horses.

Flunixin meglumine and phenylbutazone are nonsteroidal anti-inflammatory drugs commonly used for the management of colic, endotoxemia, and musculoskeletal disorders in equids. Although it is not usually recommended, there appears to be an increasing trend to use nonsteroidal anti-inflammatory drugs in combination to enhance or prolong their effects. Therefore, we studied the effect of concurrent administration of flunixin (1.1 mg/kg of body weight, IV) as flunixin meglumine and phenylbutazone (2.2 mg/kg, IV) on the pharmacokinetics of each drug and on in vitro thromboxane B2 production. Pharmacokinetic variables calculated for each drug when given alone and in combination were similar to those reported. Serum thromboxane B2 production was significantly (P = 0.05) suppressed for 12, 8, and 24 hours after administration of flunixin, phenylbutazone, and the drugs in combination, respectively. These results indicate that although concurrent administration of these drugs at the aforementioned dosages does not alter either drug disposition or clearance, it prolongs their pharmacologic effect.

The role of prostaglandin F2 alpha (PGF2 alpha) in embryonic loss following induced endotoxemia was studied in mares that were 21 to 44 days pregnant. Thirteen pregnant mares were treated with a nonsteroidal anti-inflammatory drug, flunixin meglumine, to inhibit the synthesis of PGF2 alpha caused by Salmonella typhimurium endotoxin given IV. Flunixin meglumine was administered either before injection of the endotoxin (group 1, -10 min; n = 7), or after endotoxin injection into the mares (group 2, 1 hour, n = 3; group 3, 2 hours, n = 3); 12 pregnant mares (group 4) were given only S typhimurium endotoxin. In group 4, the secretion of PGF2 alpha, as determined by plasma 15-keto-13,14-dihydro-PGF2 alpha concentrations, was biphasic, initially peaking at 30 minutes followed by a second, larger peak approximately 105 minutes after the endotoxin was given IV. When flunixin meglumine was administered at -10 minutes, synthesis of PGF2 alpha was inhibited for several hours, after administration of flunixin meglumine at 1 hour, the second secretory surge of PGF2 alpha was blocked, and administration of the drug at 2 hours did not substantially modify the secretion of PGF2 alpha. Plasma progesterone concentrations were unchanged after endotoxin injections were given in group 1. In group 2, progesterone values decreased < 2 ng/ml and remained low for several days. In group 3 and group 4, progesterone concentrations decreased to values < 0.5 ng/ml by 48 hours after endotoxin injections were given. Pregnancy continued in all 7 mares in group 1; in group 2, pregnancy continued in 2 of 3 mares; and in group 3, none of the 3 mares was pregnant by 4 days after endotoxin administration. The abortifacient effect of endotoxemia in mares < 2 months pregnant is mediated indirectly through the secretion of PGF2 alpha; compromised luteal activity and inadequate progesterone secretion are the primary causes of fetal death. Although flunixin meglumine administration can be used to prevent loss of pregnancy in cases of endotoxemia, it must be initiated at an early stage of the endotoxemia, that is, when clinical signs are often not yet apparent.

OBJECTIVE: To assess the analgesic efficacy of an IV constant rate infusion (CRI) of a morphine-lidocaine-ketamine (MLK) combination in calves undergoing umbilical herniorrhaphy. ANIMALS: 20 weaned Holstein calves with umbilical hernias. PROCEDURES: Calves were randomly assigned to receive a CRI of an MLK solution (0.11 mL/kg/h; morphine, 4.8 μg/kg/h; lidocaine, 2.1 mg/kg/h; and ketamine, 0.42 mg/kg/h) for 24 hours (MLK group) or 2 doses of flunixin meglumine (1.1 mg/kg, IV, q 24 h) and a CRI of saline (0.9% NaCl) solution (0.11 mL/kg/h) for 24 hours (control group). The assigned CRI was begun after anesthesia induction. A pain-scoring system and incisional algometry were used to assess pain, and blood samples were obtained to measure serum cortisol concentration at predetermined times for 120 hours after CRI initiation. RESULTS: Mean pain scores did not differ significantly between the MLK and control groups at any time. Mean algometry score for the MLK group was significantly greater (calves were less responsive to pressure) than that for the control group at 4 hours after CRI initiation. Mean cortisol concentration decreased over time for both groups and was significantly greater for the MLK group than the control group at 1, 4, and 18 hours after CRI initiation. CONCLUSIONS AND CLINICAL RELEVANCE: A CRI of MLK provided adequate postoperative analgesia to calves that underwent umbilical herniorrhaphy. However, the technical support required for CRI administration limits its use to hospital settings. Kinetic analyses of MLK infusions in cattle are necessary to establish optimal dosing protocols and withdrawal intervals.

Objective-To determine whether the nonsteroidal anti-inflammatory drugs (NSAIDs) carprofen, flunixin meglumine, and phenylbutazone have cyclooxygenase (COX)-independent effects that specifically inhibit activation of the proinflammatory transcription factor nuclear factor kappa B (NfκB). Study Population-Purified ovine COX-1 and -2 and cultures of RAW 264.7 murine macrophages. Procedure-The COX-1 and -2 inhibitory effects of the NSAIDs were tested in assays that used purified ovine COX-1 and -2. Prostaglandin production was analyzed by use of a radioimmunoassay. Inhibitory effects of these drugs on lipopolysaccharide (LPS)- induction of inducible nitric oxide synthase (iNOS) and LPS-stimulated translocation of NfκB were determined by use of RAW 264.7 murine macrophages. Results-Flunixin meglumine and phenylbutazone were selective inhibitors of COX-1. Carprofen and flunixin meglumine, but not phenylbutazone, inhibited LPS-induction of iNOS. Carprofen and, to a lesser degree, flunixin meglumine had inhibitory effects on NFκB activation. Conclusions and Clinical Relevance-The ability of drugs such as carprofen and flunixin meglumine to inhibit activation of NfκB-dependent genes such as iNOS, in addition to their effects on COX, suggests an additional mechanism for their anti-inflammatory effects and may explain the ability of flunixin meglumine to be an effective inhibitor of the effects of endotoxin in horses with endotoxemia.