Tolmetin sodium-loaded thermosensitive mucoadhesive liquid suppositories for rectal delivery; strategy to overcome oral delivery drawbacks.

Tolmetin sodium (TS) is a nonsteroidal anti-inflammatory drug (NSAID) indicated for treatment of musculoskeletal issues. As other NSAID, TS displays a marked side effects on the gastro-intestinal (GI) tract after oral administration. Traditional solid suppositories can cause pain and discomfort for patients, may reach the end of the colon; consequently, the drug can undergo the first-pass effect. TS liquid suppository (TS-LS) was developed to enhance patient compliance and rectal mucosal safety in high-risk patients receiving highly NSAID therapy. This work was conducted to optimize and evaluate Poloxamer P407/P188-based thermoresponsive TS-LS by using mucoadhesive polymers such as methylcellulose (MC). TS-LS was prepared by cold method and characterized their in vitro physicochemical properties as gelation temperature (GT), gel strength, bioadhesive properties, and in vitro release. The safety of the prepared suppository on rectum, stomach, and liver was evaluated histologically. Pharmacokinetic analyses were performed to compare rectal TS-LS to orally Rhumtol® capsules. The results showed that the optimized TS-LS; composed of P407/P188/MC (21/9/0.5% w/w) displayed gelation at rectum temperature ∼32.90 °C, gel strength of 21.35 s and rectal retention force at the administration site of 24.25 × 102 dyne/cm2. Moreover, TS-LS did not cause any morphological damage to the rectal tissues. Pharmacokinetic parameters of optimized TS-LS formulation revealed 4.6 fold increase in bioavailability as compared to Rhumtol® capsules. Taken together, the results demonstrated that liquid suppository is a potential and physically safe rectal delivery carrier for improvement rectal bioavailability and in vivo safety of TS.

Neutrophil depletion protects against zomepirac-induced acute kidney injury in mice.

Acyl glucuronide (AG) metabolites of carboxylic acid-containing drugs have been implicated in drug toxicity. Zomepirac (ZP) is a non-steroidal anti-inflammatory drug that was withdrawn from the market because of anaphylactic reactions and renal injury. We recently established a novel mouse model of ZP-induced kidney injury by increasing zomepirac acyl-glucuronide (ZP-AG) concentration via pretreatment with tri-O-tolyl phosphate, a nonselective esterase inhibitor, and l-buthionine-(S,R)-sulfoximine, a glutathione synthesis inhibitor. Although we have shown that ZP-AG is responsible for ZP-induced kidney injury in mice, the exact pathogenic mechanisms of ZP-induced kidney injury have not been investigated yet. In this study, we aimed to investigate the role of immune cells in the pathogenesis of ZP-induced kidney injury, as a representative of AG toxicity. We found that the counts of neutrophils and inflammatory monocytes increased in the blood of mice with ZP-induced kidney injury. However, clodronate liposome- or GdCl3-induced monocyte and/or macrophage depletion did not affect blood urea nitrogen and plasma creatinine levels in mice with ZP-induced kidney injury. Neutrophil infiltration into the kidneys was observed in mice with ZP-induced kidney injury, whereas anti-lymphocyte antigen 6 complex, locus G (Ly6G) antibody pretreatment prevented the renal neutrophil infiltration and partially protected against ZP-induced kidney injury. The mRNA expression of neutrophil-infiltrating cytokines and chemokines, interleukin-1α and macrophage inflammatory protein-2α, increased in mice with ZP-induced kidney injury, whereas pretreatment with anti-Ly6G antibody resulted in a marked reduction of their expression. These results suggest that ZP-AG might be involved in kidney injury, partly via induction of neutrophil infiltration. Therefore, this study may provide an important understanding on toxicological role of ZP-AG in vivo that helps to understand toxicity of AG metabolites.

Zomepirac Acyl Glucuronide Is Responsible for Zomepirac-Induced Acute Kidney Injury in Mice.

Glucuronidation, an important phase II metabolic route, is generally considered to be a detoxification pathway. However, acyl glucuronides (AGs) have been implicated in the toxicity of carboxylic acid drugs due to their electrophilic reactivity. Zomepirac (ZP) was withdrawn from the market because of adverse effects such as renal toxicity. Although ZP is mainly metabolized to acyl glucuronide (ZP-AG) by UDP-glucuronosyltransferase, the role of ZP-AG in renal toxicity is unknown. In this study, we established a ZP-induced kidney injury mouse model by pretreatment with tri-o-tolyl phosphate (TOTP), a nonselective esterase inhibitor, and l-buthionine-(S,R)-sulfoximine (BSO), a glutathione synthesis inhibitor. The role of ZP-AG in renal toxicity was investigated using this model. The model showed significant increases in blood urea nitrogen (BUN) and creatinine (CRE), but not alanine aminotransferase. The ZP-AG concentrations were elevated by cotreatment with TOTP in the plasma and liver and especially in the kidney. The ZP-AG concentrations in the kidney correlated with values for BUN and CRE. Upon histopathological examination, vacuoles and infiltration of mononuclear cells were observed in the model mouse. In addition to immune-related responses, oxidative stress markers, such as the glutathione/disulfide glutathione ratio and malondialdehyde levels, were different in the mouse model. The suppression of ZP-induced kidney injury by tempol, an antioxidant agent, suggested the involvement of oxidative stress in ZP-induced kidney injury. This is the first study to demonstrate that AG accumulation in the kidney by TOTP and BSO treatment could explain renal toxicity and to show the in vivo toxicological potential of AGs.

Toxicity of Carboxylic Acid-Containing Drugs: The Role of Acyl Migration and CoA Conjugation Investigated.

Many carboxylic acid-containing drugs are associated with idiosyncratic drug toxicity (IDT), which may be caused by reactive acyl glucuronide metabolites. The rate of acyl migration has been earlier suggested as a predictor of acyl glucuronide reactivity. Additionally, acyl Coenzyme A (CoA) conjugates are known to be reactive. Here, 13 drugs with a carboxylic acid moiety were incubated with human liver microsomes to produce acyl glucuronide conjugates for the determination of acyl glucuronide half-lives by acyl migration and with HepaRG cells to monitor the formation of acyl CoA conjugates, their further conjugate metabolites, and trans-acylation products with glutathione. Additionally, in vitro cytotoxicity and mitochondrial toxicity experiments were performed with HepaRG cells to compare the predictability of toxicity. Clearly, longer acyl glucuronide half-lives were observed for safe drugs compared to drugs that can cause IDT. Correlation between half-lives and toxicity classification increased when "relative half-lives," taking into account the formation of isomeric AG-forms due to acyl migration and eliminating the effect of hydrolysis, were used instead of plain disappearance of the initial 1-O-ß-AG-form. Correlation was improved further when a daily dose of the drug was taken into account. CoA and related conjugates were detected primarily for the drugs that have the capability to cause IDT, although some exceptions to this were observed. Cytotoxicity and mitochondrial toxicity did not correlate to drug safety. On the basis of the results, the short relative half-life of the acyl glucuronide (high acyl migration rate), high daily dose and detection of acyl CoA conjugates, or further metabolites derived from acyl CoA together seem to indicate that carboxylic acid-containing drugs have a higher probability to cause drug-induced liver injury (DILI).

GSSG/GSH ratios in cryopreserved rat and human hepatocytes as a biomarker for drug induced oxidative stress.

The formation of reactive oxygen species (ROS) could cause cellular damage and eventually lead to apoptosis and necrosis. The ratio between oxidized glutathione and reduced glutathione (GSSG-to-GSH ratio) has been used as an important in vitro and in vivo biomarker of the redox balance in the cell and consequently of cellular oxidative stress. This paper optimizes a LC-MS/MS method for the simultaneous determination of GSH and GSSG. The proposed method is based on the derivatization of reduced GSH using iodoacetic acid (IAA) in order to prevent its rapid oxidation to GSSG during sample preparation. The optimized analytical method was applied to evaluate the effect of different pharmaceutical agents on GSSG-to-GSH ratio in cryopreserved rat and human hepatocytes in culture. Hepatocyte viabilities were also determined at the same time by using the WST-1 assay as a direct measurement of cell mitochondrial respiration. The results obtained demonstrate that cryopreserved rat and human hepatocytes in culture are reliable in vitro models for the evaluation of cellular oxidative stress. In addition, the GSSG-to-GSH ratio measurements could be a biomarker of hepatotoxicity providing similar results to those of cytotoxicity assay.

Differential involvement of mitochondrial dysfunction, cytochrome P450 activity, and active transport in the toxicity of structurally related NSAIDs.

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used in the treatment of pain and inflammation. However, this group of drugs is associated with serious adverse drug reactions. Previously, we studied the mechanisms underlying toxicity of the NSAID diclofenac using Saccharomycescerevisiae as model system. We identified the involvement of several mitochondrial proteins, a transporter and cytochrome P450 activity in diclofenac toxicity. In this study, we investigated if these processes are also involved in the toxicity of other NSAIDs. We divided the NSAIDs into three classes based on their toxicity mechanisms. Class I consists of diclofenac, indomethacin and ketoprofen. Mitochondrial respiration and reactive oxygen species (ROS) play a major role in the toxicity of this class. Metabolism by cytochrome P450s further increases their toxicity, while ABC-transporters decrease the toxicity. Mitochondria and oxidative metabolism also contribute to toxicity of class II drugs ibuprofen and naproxen, but another cellular target dominates their toxicity. Interestingly, ibuprofen was the only NSAID that was unable to induce upregulation of the multidrug resistance response. The class III NSAIDs sulindac, ketorolac and zomepirac were relatively non-toxic in yeast. In conclusion, we demonstrate the use of yeast to investigate the mechanisms underlying the toxicity of structurally related drugs.

Non-steroidal anti-inflammatory agents, tolmetin and sulindac, inhibit liver tryptophan 2,3-dioxygenase activity and alter brain neurotransmitter levels.

Hepatic tryptophan 2,3-dioxygenase (TDO) is one of the rate-limiting enzymes in tryptophan catabolism and plays an important role in regulating the physiological flux of tryptophan into relevant metabolic pathways. In this study, we determined the effect of the non-steroidal anti-inflammatory agents, tolmetin and sulindac, on rat liver TDO activity and the subsequent changes in the hippocampal and striatal neurotransmitter levels. The amount of melatonin produced by the pineal gland was also measured using high performance liquid chromatography (HPLC). Treatment of rats with tolmetin or sulindac (5 mg/kg/bd for 5 days) significantly inhibited liver TDO activity. The results show that whilst tolmetin and sulindac increase serotonin levels in the hippocampus, these agents also significantly reduce dopamine levels in the striatum. Tolmetin, but not sulindac, increased the amount of melatonin produced by the pineal gland. The results of this study suggest that whilst tolmetin and sulindac may be beneficial for patients suffering from depression, these agents also have the potential to induce adverse effects in patients suffering with neurological disorders such as Parkinson's disease.

Celosomy is associated with prenatal exposure to cyclooxygenase inhibitors.

Celosomy is a term used for a group of congenital anomalies characterized by opening of the somatic wall with evisceration. The most common types of celosomy are gastroschisis and omphalocele. They have been associated with maternal age, cigarette smoking, environmental pollution, as well as prenatal exposure to vasoconstrictors and recreational drugs. The aim of this study was to evaluate the effect of prenatal exposure to various selective and non-selective cyclooxygenase-2 (COX-2) inhibitors on the abdominal wall defects in rat. A retrospective statistical analysis was performed on the basis of data collected in our laboratory in the years 1997-2004, during different teratological studies with COX-inhibitors (aspirin, DFU, DuP-697, ibuprofen, paracetamol, piroxicam, propyphenazone, tolmetin). Out of 6744 live born fetuses celosomy was revealed only in four animals exposed to different non-selective COX inhibitors. A single case of gastroschisis was also found in a rat exposed to the selective COX-2 inhibitor. The fetal body weight was significantly lower in COX-exposed group of fetuses when compared with untreated control. It was also significantly decreased in non-malformed fetuses prenatally exposed to COX inhibitors when compared with untreated control. The fetal body weight and length were lower in fetuses born with gastroschisis than with omphalocele. However, when animals with both anomalies were pooled in one group the mean fetal body weight was marginally lower (p = 0.0523) when compared with non-malformed group, while no statistically significant differences were found for fetal length. The pooled statistical analysis done for the concurrent and our own historic data showed that only aspirin statistically increased the risk of abdominal wall defects in rat fetuses. The expected ratio for aspirin is 56.41 per 10,000 offsprings (p < 0.05), which is over 10-times higher than ratio for all non-selective COX inhibitors, including aspirin (6.01/10,000; p < 0.05). No differences were found for selective COX-2 inhibitors. It could be stressed that aspirin, unlike other non-selective and selective COX-2 inhibitors increases the risk of the abdominal wall defects, which are observed more often in growth-retarded fetuses.

In vitro and in vivo studies on acyl-coenzyme A-dependent bioactivation of zomepirac in rats.

Zomepirac [ZP, 5-(chlorobenzoyl)-1,4-dimethylpyrrole-2-acetic acid] was withdrawn from the market because of unpredictable allergic reactions that may have been caused by ZP-protein adducts formed by reaction of the reactive acyl glucuronide of ZP (ZP-O-G) with endogenous proteins. To test the hypothesis that the reactive ZP acyl coenzyme A thioester (ZP-CoA) was formed and potentially could contribute to formation of ZP-protein adducts, we investigated the acyl CoA-dependent metabolism of ZP in freshly isolated rat hepatocytes (1 mM) and in vivo (100 mg ZP/kg, ip) in rat livers (2 h after dose administration), rat bile (0-4 h), and rat urine (0-24 h). ZP-CoA was detected in freshly isolated hepatocytes and in vivo in rat livers by LC/MS/MS. In addition, the ZP glycine conjugate (ZP-Gly) and ZP taurine conjugates (ZP-Tau) were identified by LC/MS/MS in rat hepatocytes and in vivo in rat livers, rat urine, and rat bile. The identities of ZP-CoA, ZP-Gly, and ZP-Tau were confirmed by comparison of retention times and MS/MS spectra with those of authentic standards. Moreover, the ZP acyl carnitine ester was detected in rat urine and rat bile based upon (i) the chlorine isotope pattern, (ii) MS/MS spectra showing significant ions characteristic for carnitine (m/z 60, 144 and loss of m/z 59) and ZP (m/z 139), and (iii) accurate mass measurements with a mass accuracy of 0.2 ppm. ZP-CoA serves as an obligatory intermediate in the formation of ZP-Gly, ZP-Tau, and ZP carnitine ester, and it is therefore of mechanistic significance that these conjugates were identified. Finally, time-dependent concentration profiles obtained in experiments with rat hepatocytes and in vivo from quantitative analysis of rat livers indicate that ZP-CoA, in addition to ZP-O-G, may contribute to formation of the potentially toxic covalent ZP-protein adducts.

Developmental toxicity evaluation of ibuprofen and tolmetin administered in triple daily doses to Wistar CRL:(WI)WUBR rats.

BACKGROUND: Ibuprofen and tolmetin are popular non-steroidal anti-inflammatory drugs. Previous animal studies taken with single daily doses showed their good prenatal tolerability. However, since both cyclooxygenase (COX) inhibitors have a short half-life, the current report presents drug developmental effects after triple daily doses administration, as they are used in human. METHODS: Drugs were separately, orally dosed to pregnant rats triple daily 8 hr apart from day 8 to 21 (GD=1-plug day). The total daily doses were set at 25.5, 255.0, and 600.0 mg/kg for ibuprofen and 25.5, 255.0, and 2550.0 mg/kg for tolmetin. Fetuses were delivered on GD 21 and routinely examined. Comprehensive clinical and developmental measurements were done. RESULTS: Maternal toxicity and intrauterine growth retardation were found in groups exposed to the highest doses of both drugs. An increase of external variations was reported in groups exposed to the middle and highest dose of ibuprofen and to the highest dose of tolmetin. Skeletal variations were significantly different only in litters treated with the highest doses of the drugs. Pooled statistical analysis showed a higher incidence of midline and ventricular septal (VSD) defect in rat fetuses exposed to COX inhibitors when compared with historical control data. For ibuprofen, the influence on VSD was similar to aspirin. CONCLUSION: Both COX inhibitors were toxic to dams in the highest doses evaluated, which caused a significantly greater incidence of intrauterine growth retardation and developmental variations.

Investigating the TNP-OVA and direct popliteal lymph node assays for the detection of immunostimulation by drugs associated with anaphylaxis in humans.

Using current animal models, it is not possible to identify low-molecular-weight compounds (LMWCs) that are likely to be associated with anaphylaxis. It is generally accepted that the ultimate effector mechanism involves drug-induced IgE antibody. The objective of the present study was to determine if diclofenac, zomepirac and glafenine, which are associated with anaphylaxis in humans, have immunostimulating potential in the murine TNP-OVA (trinitrophenyl-ovalbumin) popliteal lymph node assay (PLNA), and more specifically to determine if the immunostimulation caused by these LMWCs results in IgE antibody production. These LMWCs were chosen because both zomepirac and glafenine were removed from the market due to high association with anaphylaxis, and diclofenac, which remains on the market, is frequently associated with anaphylaxis. In addition to conducting a TNP-OVA PLNA, the immunostimulating potential of these compounds was examined in the direct PLNA. When co-administered with TNP-OVA, all three LMWCs caused dose-dependent (0.25, 0.50, 1.00 and 1.25 mg) increases in popliteal lymph node (PLN) weight and cellularity that were observed beginning with the 0.25-mg dose. In addition, beginning with the 0.25-mg dose, all three compounds caused dose-dependent increases in TNP-OVA specific IgM and IgG(1) antibody-forming cells (AFCs). Diclofenac induced an isotype switch and caused a dose-dependent increase in the number of IgE AFCs with no detectable IgG(2a) AFCs and minimal high-dose-only IgG(2b) AFCs. Zomepirac induced IgE, IgG(2a) and IgG(2b) AFCs following the injection of 0.50 mg only, and glafenine induced IgE, IgG(2a) and IgG(2b) AFCs following the injection of 0.50-1.00 mg. In the direct PLNA, diclofenac caused dose-dependent increases in PLN weight and cellularity that were observed beginning with dose of 0.50 mg, whereas zomepirac failed to increase any PLN parameter and glafenine only increased the PLN weight. These results suggest that diclofenac, zomepirac and glafenine are immunostimulating LMWCs in the TNP-OVA PLNA with the potential to induce IgE antibody against a co-administered hapten-conjugate. Furthermore, these results suggest that the TNP-OVA PLNA offered significant advantages over the direct PLNA. Although it is not realistic to suggest that a single assay, based on a low number of test compounds, can identify all LMWCs with the potential to cause anaphylaxis in humans, these observations do demonstrate the potential utility of the PLNAs in examining LMWC-induced immunomodulation and support further development and investigation of the assays.

Stereoselective and substrate-dependent inhibition of hepatic mitochondria beta-oxidation and oxidative phosphorylation by the non-steroidal anti-inflammatory drugs ibuprofen, flurbiprofen, and ketorolac.

Non-steroidal anti-inflammatory drugs (NSAIDs) cause a range of adverse effects, some of which have been associated with perturbances of lipid metabolic pathways. Previous data demonstrating stereoselective formation of the CoA thioester of R-ibuprofen in particular were suggestive of possible stereoselective effects on lipid metabolism. Our aim was to characterise the relative stereoselectivity of the effects of ibuprofen, flurbiprofen, and ketorolac (0.01-1.0 mM) on both the beta-oxidation of palmitate and oxidative phosphorylation in rat hepatic mitochondria as a means of dissecting prostaglandin related from non-prostaglandin-related events. Beta-oxidation was inhibited stereoselectively by R-ibuprofen (P = 0.015), non-stereoselectively by R- and S-flurbiprofen (P = 0.002 and P = 0.004, respectively), and was essentially unaffected by either enantiomer of ketorolac. At 0.25 mM, inhibition by R-ibuprofen and both flurbiprofen enantiomers was partially reversed by increasing CoA concentrations (0-200 microM). Mitochondrial respiration was moderately inhibited by both enantiomers of ibuprofen and flurbiprofen (P < 0.01), but only by high concentrations (> or = 1 mM) of the enantiomers of ketorolac (P < 0.01). Uncoupling of oxidative phosphorylation measured as stimulation of State 4 respiration contributed to these effects. The data support interactions involving both stereoselective CoA-dependent and non-CoA-dependent mechanisms. The plasma drug concentrations required to achieve these effects are not likely to be attained in the majority of patients, although these concentrations are achievable in the gastrointestinal tract and may contribute to the well-known spectrum of adverse effects in this organ. Some patients do experience systemic adverse events which may be mediated by these mechanisms.

Stereospecific pharmacokinetics and toxicodynamics of ketorolac after oral administration of the racemate and optically pure enantiomers to the rat.

To determine the stereospecific pharmacokinetics and gastrointestinal permeability (GI) changes (surrogate measures of toxicity) in the rat following oral administration of S, R, and racemic ketorolac (KT), optically pure enantiomers (S and R 2.5 mg/kg), and racemic KT (5 mg/kg) were administered orally to male Sprague-Dawley rats and plasma samples were collected for 6 h post-dose for pharmacokinetic assessments. KT-induced changes in GI permeability were assessed using sucrose and 51Cr-EDTA as markers of gastroduodenal and distal intestinal permeability, respectively. After the racemate, R-KT was predominant in plasma (AUC S/R, 0.45). No significant differences in pharmacokinetic indices were evident following administration of the racemate as compared with individual enantiomers. In plasma, there was only negligible S-KT after administration of R-KT. After S-KT, on the other hand, AUC of R-KT was found to be 6.7% of that of S-KT. Both permeability markers showed considerable interanimal variability. Gastroduodenal permeability was significantly increased from baseline by the racemate but not by either of the two enantiomers administered alone. Permeability to 51Cr-EDTA was not significantly increased above baseline for any of the treatments. The plasma concentration of R-KT found after administration of S-KT may be from the < 2% chiral impurity which appears magnified due to its slower clearance as compared with its antipode. There is no evidence of a pharmacokinetic interaction between the enantiomers. Since 2.5 mg/kg S-KT is somewhat less toxic on the gastroduodenum than 5 mg/kg racemate, it may be a safer alternative to the latter, at least in the rat model.

Intra-articular injection of ketorolac in the rat knee joint: effect on articular cartilage and synovium.

We have investigated the effects of intra-articular (i.a.) administration of ketorolac in the rat knee joint. Thirty Sprague-Dawley rats were given 0.25 ml of a standard preparation of ketorolac trometamol (10 mg ml-1) by injection into the right knee joint and 0.25 ml of 0.9% physiological saline solution by injection into the left knee as a control. Ten rats were killed at 24 h, 10 at 48 h and 10 at 5 days after injection. The joints were prepared and sectioned for histological examination. There was significantly more inflammation in those knees that had received i.a. ketorolac at all times of examination, with the most severe changes occurring 5 days after injection. A further group of 10 rats were given 0.25 ml of 10% w/v ethanol in physiological saline (similar to the vehicle for parenteral ketorolac) injected into the knee joint, with a 0.9% saline control injected in the other knee. These rats were then killed at 5 days (as this was the time interval after which we found the maximum inflammatory response in the earlier phase of our study). The joints were prepared and examined histologically. We feel that the absence of inflammatory changes in these joints make it unlikely that ethanol was responsible for the inflammation produced by ketorolac injection.

Factors influencing ketorolac-associated perioperative renal dysfunction.

UNLABELLED: Nonsteroidal antiinflammatory drugs (NSAIDs) are useful for the treatment of postoperative pain, but there is continuing concern about adverse effects on renal function. We studied the renal effects of ketorolac in an animal model using Fischer 344 rats undergoing isoflurane anesthesia and laparotomy. Treatment groups--control (C), ketorolac (5 mg x kg(-1) x d(-1)) (K), large-dose ketorolac (15 mg x kg(-1) x d(-1)) (KH), dehydration-ketorolac (5 mg x kg(-1) x d(-1)) (DK), gentamicin (20 mg x kg(-1) x d(-1)) (G), and gentamicin (20 mg x kg(-1) x d(-1)) with ketorolac (5 mg x kg(-1) x d(-1)) (GK)--each comprised 10 animals. Renal function was assessed before laparotomy and after 3 treatment days using concurrent paraaminohippurate and iothalamate clearances, respectively, to estimate renal plasma flow and glomerular filtration rate, and by measuring serum and urine electrolytes, osmolality, urea, and creatinine. A significant increase in serum potassium was found in the GK and DK groups. There were no major changes in renal function in the C, K, KH, and DK groups. Mild renal dysfunction was found in the G group. We found severe and consistent changes in renal function, accompanied by severe, widespread histological changes of acute tubular necrosis, in the GK group. In this postoperative rat model, the combination of ketorolac and gentamicin was deleterious to renal function. IMPLICATIONS: We examined the renal effects of the nonsteroidal antiinflammatory drug ketorolac. Renal function was measured in rats before and after surgery and 3 days' drug administration; the kidneys studied by using microscopy. Only ketorolac plus the antibiotic gentamicin produced marked changes in kidney function and structure.

Regulating the cancer-inducing potential of non-steroidal anti-inflammatory drugs: some lessons from the 1970s and 1980s.

This article systematically examines government regulation of medicines in the U.K. and the U.S. with specific reference to carcinogenic risk assessment. By taking four non-steroidal anti-inflammatory drugs (NSAIDs) as case studies, it is argued that there have been inconsistencies between regulatory practice and the scientific standards supposed to have been upheld by drug regulatory agencies. Moreover, those inconsistencies are shown to form a trend over time which suggests an erosion and neglect of regulatory rigour during the 1980s. This takes the form of awarding the benefit of the many scientific doubts in carcinogenicity testing to manufacturers rather than to patients.

Chiral kinetics and dynamics of ketorolac.

It has been shown that the analgesic and cyclooxygenase inhibitor activity of ketorolac tromethamine (KT), which is marketed as the racemic mixture of (-)S and (+)R enantiomers, resides primarily with (-)S ketorolac and that the ulcerogenic activity of this agent also resides in (-)S ketorolac. Resolution of individual enantiomers for analysis in plasma samples has been accomplished by two methods: derivatization to form diastereomers that are separated by HPLC, or direct HPLC using a chiral phase column. When mice and rats were given oral solutions of (-)S and (+) KT, it was found that the kinetics and interconversion of the enantiomers were species and dose dependent. Interconversion was higher in mice than in rats; when (-)S KT was administered, 71% of the area under the concentration-time curve (AUC) was due to (+)R ketorolac in mice, compared with 12% in rats. More interconversion was observed at higher doses; the percent of AUC due to (-)S ketorolac when (+)R KT was administered increased from 12% to 25% in mice and from 2% to 8% in rats. In general, more interconversion occurred from (-)S to (+)R ketorolac in the animal studies. Human subjects were given single oral solution doses of racemic KT (30 mg), (-)S KT (15 mg), and (+)R KT (15 mg). The plasma concentrations of (-)S ketorolac were lower than (+)R ketorolac at all sample times after racemic KT (22% of the AUC was due to (-)S ketorolac). When (+)R KT was administered, (-)S ketorolac was not detectable and interconversion was essentially 0%. When (-)S KT was administered, significant levels of (+)R ketorolac were detectable and interconversion was 6.5%. After all doses, plasma half-life was shorter and clearance greater for (-)S ketorolac than for (+)R ketorolac. Thus, in humans very little or no interconversion of (+)R to (-)S was observed, and interconversion of (-)S to (+)R was minimal (6.5%). These data demonstrate that the kinetics and interconversion of the enantiomers of ketorolac is different in animals and humans as well as from most other NSAIDs. This may be due to more rapid excretion or metabolism of (-)S ketorolac and a different mechanism of interconversion.

Renal hemodynamic effects of chronic ketorolac tromethamine treatment in aged lean and obese Zucker rats.

Ketorolac tromethamine is a relatively new non-steroidal anti-inflammatory drug (NSAID), with potent analgesic activity. Similar to other NSAIDs, ketorolac has the potential to impair renal function. To assess the renal hemodynamic impact of the ketorolac in aged lean and obese rats, ketorolac was orally administered to 46-week-old lean and obese Zucker rats for two weeks. Ketorolac was mixed with rat chow in a manner to provide a dose equivalent to 15 mg/kg body weight/day. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured under anesthesia by standard inulin and p-aminohippuric acid clearance method, respectively. Urinary prostaglandin (PG) E2 excretion was measured before and after ketorolac treatment. Ketorolac treatment significantly reduced obese rat GFR (0.47 +/- 0.08 vs 0.78 +/- 0.03 ml/min/g, p < 0.002) and ERPF (1.12 +/- 0.14 vs 2.36 +/- 0.26 ml/min/g, p < 0.001) relative to obese control rats. In comparison, ketorolac did not significantly alter lean rats GFR (0.77 +/- 0.04 vs 0.91 +/- 0.06 ml/min/g) or ERPF (1.92 +/- 0.20 vs 2.48 +/- 0.15 ml/min/g) relative to lean control rats. Chronic ketorolac treatment significantly reduced hematocrit by 20 and 30 percent in lean and obese rats relative to controls, respectively. The renal vascular resistance was significantly increased with ketorolac treatment in obese rats (36 +/- 4 vs 79 +/- 14 mmHg/ml/min, p < 0.001) but not lean rats (28 +/- 3 vs 38 +/- 5 mmHg/ml/min, NS) relative to corresponding controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Blockade of the antinociceptive activity of centrally administered ketorolac by nor-binaltorphimine.

Antinociceptive activity of intracerebroventricularly administered ketorolac tromethamine was evaluated in mice by measuring inhibition of abdominal stretching induced by p-phenylquinone. Ketorolac tromethamine produced dose-dependent antinociception with an ED50 of 7.34 micrograms/mouse (4.97-10.82) and a maximal effect at 30 micrograms. Selective antagonists of opioid receptors were used to determine ketorolac's mechanism of action. The ketorolac tromethamine-induced antinociception was not blocked by the mu- and delta-opioid receptor antagonists, naloxone and ICI-174,864 (N,N-diallyl-Tyr-Aib-Aib-Phe-Leu), respectively; however, the kappa-opioid receptor antagonist nor-binaltorphimine dihydrochloride significantly blocked this effect. These findings suggest that activation of kappa-opioid receptors appears to play a role in the mechanism of the antinociceptive effect of ketorolac tromethamine. Ketorolac tromethamine may induce the release of endogenous kappa-opioids to produce central nervous system antinociception.

Comparison of ketorolac tromethamine with other injectable nonsteroidal anti-inflammatory drugs for pain-on-injection and muscle damage in the rat.

The local tolerance of ketorolac tromethamine (Toradol, Syntex) was compared with that of four other injectable nonsteroidal anti-inflammatory drugs (NSAIDs) (diclofenac sodium, piroxicam, ketoprofen, and metamizol magnesium) in the rat paw-lick/muscle irritation assay as described previously. All drugs were tested at concentrations approved for clinical use. After subplantar (footpad) injection, ketorolac produced virtually no pain-on-injection as assessed by the number of paw-lick/lift responses during a 15 min observation period. The other NSAIDs produced slight to moderate paw-lick/lift responses. Redness and swelling at the injection site were less severe for ketorolac than for the other NSAIDs. After intramuscular (i.m.) injection, all of the NSAIDs produced some degree of muscle damage, as assessed histopathologically 24 h after injection. The lesions, consisting primarily of muscle degeneration, were less severe for ketorolac than for the other NSAIDs. Ketorolac and metamizol produced the smallest elevations in serum creatine kinase, as measured 2 h after i.m. dosing, not significantly different from isotonic saline. Overall, ketorolac was better tolerated in the assay than the other injectable NSAIDs, thereby suggesting the possibility of improved local tolerance on clinical use.