Comparison of in vitro effects of flunixin and tolfenamic acid on human leukocyte and platelet functions

Administration of the nonsteroidal anti-inflammatory drug tolfenamic acid at embryo transfer improves maintenance of pregnancy and embryo survival in recipient mice

PURPOSE

To evaluate the effect of the nonsteroidal anti-inflammatory drugs tolfenamic acid and flunixin meglumine in pregnancy rate and embryo survival of recipient mice subjected to embryo transfer.

METHODS

A total of 142 recipient females were transferred with 2,931 embryos and treated with a single injection of tolfenamic acid (1 mg/kg; n = 54 females with 1,129 embryos), flunixin meglumine (2.5 mg/kg; n = 46 females with 942 embryos), or bi-distilled water (10 mL/kg) as control group (n = 42 females with 860 embryos). Pregnancy was checked 2 weeks after embryo transfer, delivery was registered on the due date, and litter size was recorded on Day 7 after birth.

RESULTS

Pregnancy rate of tolfenamic acid treated females was significantly higher than flunixin group (P < 0.05) and showed a tendency to be higher when compared to the control group (P = 0.06). The number of pups born from transferred embryos in pregnant females was significantly higher for both treatment groups compared to controls (P < 0.05). Number of pups from total transferred embryos was higher for both treatment groups (P < 0.05) when compared to controls.

CONCLUSION

The use of tolfenamic acid at the time of embryo transfer improves both pregnancy rate and number of live pups in recipient mice, with optimal effects observed with flunixin meglumine. We suggest that the use of tolfenamic acid has beneficial effects on the maintenance of pregnancy and embryo survival in recipient mice, which should be taken into account for further studies in other mammalian females.

Measurement of cyclooxygenase inhibition in vivo: a study of two non-steroidal anti-inflammatory drugs in sheep

The anti-inflammatory effects of the non-steroidal anti-inflammatory drugs phenylbutazone (PBZ) and flunixin meglumine (FM) and the relationship between the effects and drug concentration in vivo were studied using a subcutaneous tissue-cage model in sheep. Intracaveal injection of carrageenan induced prostaglandin (PG) E2 production in tissue-cage exudate (maximal concentration, 101 nM) with significant increases in white blood cell (WBC) numbers, skin temperature over the inflamed cage and exudate leukotriene B4 (LTB4) concentration (P < 0.05). Intravenous PBZ, 4.4 mg kg-1 produced mild inhibition of exudate PGE2 generation (10%), but greater inhibition of serum TXB2 (75.3%). The IC50 for TXB2 was 36.0 microM. Phenylbutazone did not alter effects on skin temperature, WBC numbers or exudate LTB4 concentrations. Intravenous FM, 1.1 mg kg-1, significantly inhibited carrageenan-induced exudate PGE2 formation (Emax, 100%, IC50, < 0.4 nM) and serum TXB2 generation (Emax, 100%, IC50, 17 nM) for up to 32 h. Flunixin meglumine significantly inhibited the rise in skin temperature but had a limited effect on exudate WBC. Phenylbutazone and FM have distinct effects on carrageenan-induced cyclooxygenase (COX-2) and platelet COX (COX-1). Flunixin meglumine was a more potent COX inhibitor than PBZ and was more selective for the inducible form of COX in vivo.

Peripheral blood neutrophil leukotriene B4 release and migration in rheumatoid arthritis

The present study was designed to compare peripheral blood neutrophil migration and leukotriene (LT) release between patients with rheumatoid arthritis (RA) and healthy controls and to correlate the neutrophil functions with clinical disease activity. Nineteen patients with moderately active RA and 19 age and sex matched healthy volunteers participated in this study. Isolated peripheral blood neutrophils from RA patients released equal amounts of LTB4 but their random migration was enhanced as compared with neutrophils from healthy controls. LTB4 release in whole blood was significantly lower in samples from RA patients than in those from the healthy volunteers (13.5 +/- 1.4 and 19.1 +/- 1.4 ng/10(6) neutrophils respectively; P < 0.001). LTB4 release from isolated RA neutrophils correlated with the levels of C-reactive protein, duration of morning stiffness and Ritchie articular swelling index. Concentrations of hyaluronate, cyclic AMP and 13, 14-dihydro-15-keto prostaglandin were not different between patients with RA and healthy volunteers. Neither was there any difference in TXB2 production by platelets during blood clotting. In conclusion, peripheral blood neutrophils of RA patients seem to be primed and/or activated as their random migration is enhanced as compared with those of healthy volunteers. In RA, LTB4 release from peripheral blood neutrophils seems to reflect the clinical activity of the disease. However, RA neutrophils released smaller (in whole blood) or equal (isolated cells) amount of LTB4 as compared with the respective controls. These contradictory findings suggest that LTB4 release from peripheral blood neutrophils has no major role in the regulation of disease activity in rheumatoid arthritis.

Protein binding and in vitro serum thromboxane B2 inhibition by flunixin meglumine and meclofenamic acid in dog, goat and horse blood

Flunixin was highly protein bound in the serum of dogs (92.2 per cent), goats (84.8 per cent) and horses (86.9 per cent). Meclofenamic acid was also highly protein bound, although there were larger differences between the extent of the binding in dogs (90.3 per cent), goats (84.7 per cent) and horses (99.8 per cent). Both flunixin and meclofenamic acid were potent inhibitors of the in vitro generation of thromboxane (Tx) B2 in blood. Flunixin inhibited the generation of TxB2 by 50 per cent of the maximum response (IC50) in dog, goat and horse blood at concentrations of 0.10, 0.02 and 0.04 microM respectively and by 100 per cent (Imax) at 2.07, 0.14 and 2.07 microM respectively. The IC50 values of meclofenamic acid in dogs, goats and horses were 0.77, 0.80 and 0.30 microM respectively and the Imax values were 3.93, 3.63 and 3.56 microM respectively. When the concentrations of flunixin were corrected for protein binding, it was estimated that the IC50 of the unbound fractions in dogs, goats and horses were 0.008, 0.003 and 0.005 microM, respectively. Similarly corrected values for meclofenamic acid were 0.075, 0.122 and 0.001 microM respectively.

Pharmacokinetics and pharmacodynamics of tolfenamic acid in calves

Pharmacokinetic/pharmacodynamic modelling was applied to a study in which tolfenamic acid was administered intravenously to calves at a dose rate of 2 mg kg-1. The drug had a shorter mean (SEM) elimination half-life (T1/2 beta) of 2.5 (0.95) hours and a larger volume of distribution (Vdarea) of 0.98 (0.28) litre kg-1 than other non-steroidal anti-inflammatory drugs. Its body clearance was high with a mean value of 0.30 (0.06) litre kg-1 h-1. It had inhibitory effects on inflammatory exudate PGE2 and beta-glucuronidase, serum TxB2 and bradykinin-induced swelling but it did not affect exudate LTB4 concentrations. Its mean EC50 values were lower for exudate PGE2, beta-glucuronidase and bradykinin-induced swelling inhibition (0.077 [0.018]; 0.040 [0.017] and 0.030 [0.020] microgram ml-1, respectively) than for serum TxB2 inhibition (0.137 (0.079) microgram ml-1). There were also differences in its equilibration halflife, which was short for the inhibition of serum TxB2, intermediate for exudate PGE2 and beta-glucuronidase and longer for bradykinin-induced swelling. These differences may be explained by the existence of three distribution compartments relating to the different sites of action of the drug.

Inhibition of human neutrophil function by tolfenamic acid involves inhibition of Ca2+ influx

The present work was designed to study the pharmacological control of the receptor-mediated activation of human neutrophils by tolfenamic acid (2(-)[(3-chloro-2-methylphenyl)-amino]benzoic acid). Tolfenamic acid inhibited in a concentration-dependent manner the degranulation response and Ca2+ influx in neutrophils activated either by the chemotactic peptide fMLP (N-formyl-methionyl-leucylphenylalanine) or Ca2+ ionophore A23187 (calcimycin). When fMLP was used to activate neutrophils, tolfenamic acid (30 microM) reduced Ca2+ influx by 50% and degranulation by 20%. A23187-triggered Ca2+ influx and degranulation were inhibited by 60% and 40%, respectively, by 30 microM tolfenamic acid. Tolfenamic acid did not inhibit the release of Ca2+ from intracellular stores induced either by fMLP or A23187. To confirm the inhibition of receptor-mediated cation influx by tolfenamic acid, the agonist induced Mn2+ influx was studied in Ca2+ free medium. Tolfenamic acid (10-30 microM) reduced fMLP-stimulated Mn2+ influx in neutrophils in a concentration-dependent manner. The simultaneous Ca2+ release from intracellular stores was not affected. Protein kinase C activity in sonicated human neutrophils and the purified enzyme from rat brain were inhibited by the protein kinase inhibitor H-7 (1-(5-isoquinolinylsulfonyl)-2-methylpiperazine) but not by tolfenamic acid. Both failed to inhibit neutrophil degranulation induced by phorbol myristate acetate, a protein kinase C activator. Tolfenamic acid (100 microM) increased the cellular cAMP levels up to 1.3-fold in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. No effects on cellular cGMP levels were found.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacological control of human polymorphonuclear leukocyte degranulation by fenamates and inhibitors of receptor-mediated calcium entry and protein kinase C

The present work was designed to study the mechanism of inhibitory action of flufenamic and tolfenamic acids on the degranulation response of human polymorphonuclear leukocytes (PMNs). We have recently shown that fenamates inhibit PMN degranulation as well as other PMN functions at micromolar drug concentrations. However, the mechanism of their action remains unknown. To clarify this mechanism, the degranulation response was induced by agents known to activate different steps in the activation cascade in PMNs: the receptor-mediated activator fMLP (N-formyl-L-methionyl-L-leucyl-L-phenylalanine); a calcium ionophore (A23187); an inhibitor of calcium-ATPase (thapsigargin); and an activator of protein kinase C (phorbol myristate acetate, PMA). For comparison, SK&F 96365 (an inhibitor of receptor-mediated calcium entry), Ro 31-8220 (an inhibitor of protein kinase C) and ketoprofen (another cyclooxygenase inhibitor) were used. Flufenamic and tolfenamic acids inhibited A23187- and fMLP-induced degranulation in a dose-dependent manner. The thapsigargin-triggered response was reduced only slightly and that induced by PMA remained unaltered. The pattern of the inhibitory action of fenamates differed from those of Ro 31-8220 and ketoprofen. The action of fenamates resembled that of the inhibitor of receptor-mediated calcium entry, SK&F 96365, especially when A23187, fMLP or PMA were used to stimulate the cells. This prompted us to measure the effects of flufenamic and tolfenamic acids on receptor-mediated calcium entry. The two fenamates inhibited the fMLP-induced increase in intracellular free calcium in fura-2 loaded PMNs in the presence but not in the absence of extracellular calcium. The results suggest that the suppressive actions of fenamates on PMN degranulation are neither related to the activity of cyclooxygenase nor PMA-activated protein kinase C. In contrast, fenamates resemble the antagonist of receptor-mediated calcium entry, SK&F 96365, in their antagonistic action on PMN degranulation.

Pharmacodynamics of tolfenamic acid in dogs. Evaluation of dose response relationships

Tolfenamic acid was administered to beagle dogs at 2, 4 and 8 mg/kg bodyweight i.m. and the concentration of drug in plasma and in inflamed (administered carrageenan) and non-inflamed subcutaneous tissue cage fluid was measured. The concentration of thromboxane B2 in serum from blood allowed to clot under standardized conditions was determined and the concentrations of prostaglandin E2, 12-hydroxyeicosatetraenoic acid (12-HETE) and leucocyte numbers were measured in fluid from the carrageenan administered tissue cages. Skin temperature was also measured over each tissue cage following administration of drug. Tolfenamic acid displayed linear pharmacokinetics since the area under the plasma concentration time curve (AUC) values were 13.74 +/- 1.88, 29.82 +/- 6.53 and 50.52 +/- 5.73 micrograms/ml.h following administration of 2, 4 and 8 mg/kg, respectively. Tolfenamic acid proved to be a potent inhibitor of ex vivo thromboxane B2 generation in clotting blood. Maximal inhibition was greater than 80% at all dose rates and 97% at the 8 mg/kg dose rate 1 h after drug administration. It also proved to be a potent inhibitor of prostaglandin E2 production in inflammatory exudate, and significantly (P < 0.05) decreased prostaglandin E2 production at all dose levels. Tolfenamic acid did not significantly alter 12-HETE generation or white blood cell accumulation in inflammatory exudate. Tolfenamic acid significantly reduced the elevated skin temperature over carrageenan administered cages at all dose levels.