Transcriptomic response of HepG2 cells exposed to three common anti-inflammatory drugs: Ketoprofen, mefenamic acid, and diclofenac in domestic wastewater effluents.

The biological impacts of residual pharmaceuticals in the complex wastewater effluents have not been fully understood. Here, we investigated changes in the transcriptomic responses of hepatobrastoma (HepG2) cells exposed to a single or partially combined three common non-steroidal anti-inflammatory drugs (NSAIDs); ketoprofen (KPF), mefenamic acid (MFA) and diclofenac (DCF), in domestic wastewater effluents. After 48 h sub-lethal exposure to single compounds, the DNA microarray analysis identified 57-184 differently expressed genes (DEGs). The hierarchical clustering analysis and GO enrichment of the DEGs showed that gene expression profiles of the NSAIDs were distinct from each other although they are classified into the same therapeutic category. Four maker genes (i.e., EGR1, AQP3, SQSTM1, and NAG1) were further selected from the common DEGs, and their expressions were quantified by qPCR assay in a dose-dependent manner (ranging from µg/L to mg/L). The results revealed the insignificant induction of the marker genes at 1 µg/L of KPF, MFA, and DCF, suggesting negligible biological impacts of the NSAIDs on gene expression (early cellular responses) of HepG2 at typical concentration levels found in the actual wastewater effluents. Based on the quantitative expression analysis of the selected marker genes, the present study indicated that the presence of wastewater effluent matrix may mitigate the potentially adverse cellular impacts of the NSAIDs.

Renal ultrastructural alterations induced by various preparations of mefenamic acid.

Mefenamic acid (MFA) treatment is associated with a number of cellular effects that potentiate the incidence of renal toxicity. The aim of this study is to investigate the potential ultrastructural alterations induced by various preparations of MFA (free MFA, MFA-Tween 80 liposomes, and MFA-DDC liposomes) on the renal tissues. Sprague-Dawley rats were subjected to a daily dose of MFA preparations for 28 days. Renal biopsies from all groups of rats under study were processed for transmission electron microscopic examination. The findings revealed that MFA preparations induced various ultrastructural alterations including mitochondrial injury, nuclear and lysosomal alterations, tubular cells steatosis, apoptotic activity, autophagy, and nucleophagy. These alterations were more clear in rats received free MFA, and MFA-Tween 80 liposomes than those received MFA-DDC liposomes. It is concluded that MFA-DDC liposomes are less potential to induce renal damage than free MFA and MFA-Tween 80 liposomes. Thus, MFA-DDC liposomes may offer an advantage of safe drug delivery.

Electro-transformation of mefenamic acid drug: a case study of kinetics, transformation products, and toxicity.

Poor removal of many pharmaceuticals and personal care products in sewage treatment plants leads to their discharge into the receiving waters, where they may cause negative effects for aquatic environment and organisms. In this study, electrochemical removal process has been used as alternative method for removal of mefenamic acid (MEF). For our knowledge, removal of MEF using electrochemical process has not been reported yet. Effects of initial concentration of mefenamic acid, sodium chloride (NaCl), and applied voltage were evaluated for improvement of the efficiency of electrochemical treatment process and to understand how much electric energy was consumed in this process. Removal percentage (R%) was ranged between 44 and 97%, depending on the operating parameters except for 0.1 g NaCl which was 9.1%. Consumption energy was 0.224 Wh/mg after 50 min at 2 mg/L of mefenamic acid, 0.5 g NaCl, and 5 V. High consumption energy (0.433 Wh/mg) was observed using high applied voltage of 7 V. Investigation and elucidation of the transformation products were provided by Bruker software dataAnalysis using liquid chromatography-time of flight mass spectrometry. Seven chlorinated and two non-chlorinated transformation products were investigated after 20 min of electrochemical treatment. However, all transformation products (TPs) were eliminated after 140 min. For the assessment of the toxicity, it was impacted by the formation of transformation products especially between 20 and 60 min then the inhibition percentage of E. coli bacteria was decreased after 80 min to be the lowest value.

Synthesis, Biological Evaluation and Pharmacokinetic Studies of Mefenamic Acid - N-Hydroxymethylsuccinimide Ester Prodrug as Safer NSAID.

BACKGROUND: Non steroidal anti-inflammatory drugs are the most widely prescribed drugs to manage pain and inflammatory conditions, but their long term use is associated with gastrointestinal toxicity. OBJECTIVES: The study aimed to synthesize an ester-based prodrug of a non steroidal anti-inflammatory agent, mefenamic acid in order to improve the therapeutic index vis a vis to overcome the side effects such as gastrointestinal irritation and bleeding associated with the use of mefenamic acid. METHODS: The ester prodrug (MA-NH) was prepared by condensing mefenamic acid with N-hydroxymethylsuccinimide in the presence of Phosphorus oxychloride. The pharmacokinetic profile, including stability and release of mefenamic acid and N-hydroxymethylsuccinimide from the ester prodrug (MA-NH) was studied by RP- HPLC in acidic medium (pH 1.2), basic medium (pH 7.4), 80 % v/v human plasma, 10 % w/v rat intestinal homogenate and 10 % w/v rat liver homogenate (pH 7.4). RESULTS: The chemical structure of the title compound was characterized by using modern spectroscopic techniques. The prodrug was found to be stable in acid medium, but it hydrolyzed and released sufficient quantities of the drug in alkaline medium. The prodrug produced lesser number of ulcers and showed improved analgesic and anti-inflammatory activity as compared to the parent drug. CONCLUSION: The results indicate that the synthesized prodrug (MA-NH) is better in terms of analgesic and antiinflammatory activities and with less GI toxicity than the parent drug.

Assessment of in vitro antiovulatory activities of nonsteroidal anti-inflammatory drugs and comparison with in vivo reproductive toxicities of medaka (Oryzias latipes).

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used therapeutic agents; however, their pharmacological actions raise concerns about potential risks to the reproductive health of aquatic vertebrates. In the present study, a medaka ovulation assay was applied as an in vitro model to evaluate NSAID-induced antiovulatory activity. We first tested five NSAIDs, including diclofenac sodium (DCF), ketoprofen (KP), salicylic acid (SA), mefenamic acid (MA), and acetylsalicylic acid (ASA) for their antiovulatory activities toward the follicles isolated from the ovaries of spawning females. Of all the chemicals tested, DCF had the highest antiovulatory activity, with the concentration that caused 50% inhibition (IC50) (101 µM). MA was the second most potent inhibitor following DCF, but KP, SA, or ASA had little inhibitory effect on the ovulation of the follicles. The in vitro antiovulatory activity of five NSAIDs showed good correlation with data published on the inhibitory activity on human COX-2. Second, we selected DCF and SA as the most and least potent NSAIDs, respectively, and examined the effects on reproduction of intact fish in order to evaluate whether the ovulation assay was a reasonable predictor of potential reproductive effects in fish. Females exposed to DCF showed a concentration-dependent decrease in the number of spawned eggs and an increment in the gonadosomatic index (GSI), possibly due to an anovulation in the females. In contrast, neither fecundity nor the GSI of females decreased at up to 20 mg/L of SA, at which acute lethality to medaka was induced. In conclusion, the medaka ovulation assay reflected the potency of NSAID-induced antiovulatory activity and may thus serve as an in vitro model for the prediction of NSAID-induced reproductive toxicity. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1710-1719, 2016.

Identification and disposition of novel mono-hydroxyl mefenamic acid and their potentially toxic 1-O-acyl-glucuronides in vivo.

Mefenamic acid (MEF) is a widely prescribed non-steroidal anti-inflammatory drug that has been found associated with rare but severe cases of hepatotoxicity, nephrotoxicity and gastrointestinal toxicity. The formation of protein-reactive acylating metabolites such as 1-O-acyl-MEF glucuronide (MEFG) and 3'-hydroxymethyl-MEF 1-O-acyl-glucuronide is one proposed cause. In addition to the well-reported 3'-hydroxymethyl-MEF, two mono-hydroxyl-MEF (OH-MEFs) were recently identified in vitro. However, in vivo evidence is lacking and whether these OH-MEFs would be further glucuronidated to the potentially reactive 1-O-acyl-glucuronides (OH-MEFGs) is unknown. Utilizing UPLC-Q-TOF/MS and LC-MS/MS, the current study identified, for the first time, four OH-MEFs and their corresponding OH-MEFGs from plasma after a single oral administration of MEF (40 mg/kg) to rats, including an OH-MEF that has not been reported previously. The systemic exposure of these identified metabolites was high, with metabolic to parent AUC0 → 24 h ratios reaching 23-52% (OH-MEFs) and 8-29% (OH-MEFGs). These metabolites also had a long systemic exposure time in both single and 5 day multiple oral MEF-treated rats, with elimination half-lives between 9 h and > 24 h. In addition to these novel metabolites, the previously reported MEFG was also identified and its systemic exposure was found to be doubled after multiple MEF administrations. These pharmacokinetic results suggest that systemic toxicities caused by the potentially reactive MEFG and OH-MEFGs could be considerable, especially after repeated MEF treatment. Nevertheless, MEFG and OH-MEFGs had negligible uptake in the brain, indicating a minimal risk of brain toxicities. Furthermore, an in situ intestinal perfusion study revealed that during MEF absorption, it was extensively metabolized to MEFG while < 5% was metabolized to OH-MEFs and OH-MEFGs.

Herb-drug interactions between Scutellariae Radix and mefenamic acid: Simultaneous investigation of pharmacokinetics, anti-inflammatory effect and gastric damage in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Scutellariae Radix (SR), the dried root of Scutellariae baicalensis Georgi, has a lot in common with non-steroidal anti-inflammatory drugs (NSAIDs). Their similarities in therapeutic action (anti-inflammation) and metabolic pathways (phase II metabolisms) may lead to co-administration by patients with the potential of pharmacokinetic and/or pharmacodynamic interactions. The current study aims to investigate the potential interactions between SR and an NSAID, mefenamic acid (MEF), on the overall pharmacokinetic dispositions, anti-inflammatory effects and adverse effects in rats. MATERIALS AND METHODS: The current study simultaneously monitored the pharmacokinetic and pharmacodynamic interactions in a single animal. Four groups of Sprague-Dawley rats (n=7 each) received oral doses of a standardized SR extract (300mg/kg, twice daily), MEF (40mg/kg, daily), combination of SR extract and MEF, and vehicle control, respectively, for 5 days. On Day 5, blood samples were collected after first dose over 24h for the determination of (1) plasma concentrations of SR bioactive components, MEF and its metabolites by LC-MS/MS, and (2) prostaglandin E2 (PGE2) production and cyclooxygenase-2 (COX-2) gene expression by ex vivo analyses using LPS-stimulated RAW264.7 macrophage cells, ELISA and real time-PCR. After the rats were sacrificed, stomachs were isolated to assess their gross mucosal damage. Statistical comparisons were conducted using ANOVA and t-test. RESULTS: Minimal pharmacokinetic interaction between SR extract and MEF was observed. Co-administration of SR extract and MEF did not significantly alter the plasma concentration-time profile or the pharmacokinetic parameters such as Cmax, AUC0→24, Tmax or clearance. Pharmacodynamic interaction via the COX-2 pathway was observed. The PGE2 level in LPS-stimulated RAW264.7 cells treated with plasma collected from control group over the 24h sampling (AUC0→24[PGE2]) was 191981±8789pg/mlhr, which was significantly reduced to 174,780±6531 and 46,225±1915pg/mlhr by plasma collected from rats administered with SR extract and MEF, respectively. Co-administration of SR extract and MEF further potentiated the PGE2 inhibition, with an AUC0→24[PGE2] of 37013±2354pg/mlhr (p<0.05, compared to SR or MEF group). By analyzing the COX-2 gene expression, SR extract significantly prolonged the COX-2 inhibitory effect of MEF over the 24h (p<0.05). Furthermore, the MEF-induced stomach ulcer after the 5-day treatment, as evidenced by the increased gross ulcer index and sum of lesion length (p<0.05, compared to control), could be alleviated by co-administration with SR extract (p<0.05). CONCLUSIONS: Co-administration of SR extract and MEF potentiated the anti-inflammatory effects, alleviated the MEF-induced stomach adverse effect while having minimal pharmacokinetic interactions. Our findings provide insight for combination therapy of SR extract and MEF against inflammatory diseases.

Biological evaluation of bismuth non-steroidal anti-inflammatory drugs (BiNSAIDs): stability, toxicity and uptake in HCT-8 colon cancer cells.

Recent studies showed that the metal-coordinated non-steroidal anti-inflammatory drug (NSAID), copper indomethacin, reduced aberrant crypt formation in the rodent colon cancer model, while also exhibiting gastrointestinal sparing properties. In the present study, the stability and biological activity of three BiNSAIDs of the general formula [Bi(L)3]n, where L=diflunisal (difl), mefenamate (mef) or tolfenamate (tolf) were examined. NMR spectroscopy of high concentrations of BiNSAIDs (24h in cell medium, 37°C) indicated that their structural stability and interactions with cell medium components were NSAID specific. Assessment of cell viability using the [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium]bromide (MTT) assay showed that the toxicity ranking of the BiNSAIDs paralleled those of the respective free NSAIDs: diflH

Toxicity and endocrine disruption in zebrafish (Danio rerio) and two freshwater invertebrates (Daphnia magna and Moina macrocopa) after chronic exposure to mefenamic acid.

Pharmaceuticals have been frequently detected in the aquatic environment. Their potential effects on the endocrine system in wildlife are of special concern because these alterations could lead to impaired reproduction. We evaluated ecotoxicities associated with long-term exposure to mefenamic acid (MFA) and potential endocrine disruption. For this purpose, acute and chronic toxicities of MFA on several aquatic organisms, including two cladocerans, Daphnia magna and Moina macrocopa, and a teleost, Danio rerio were evaluated. The 48 h acute median effective concentration (EC50) of D. magna and M. macrocopa was 17.16 mg/L and 2.93 mg/L, respectively. In chronic toxicity test, D. magna and M. macrocopa showed significant changes in reproduction (number of young per adult) after the exposure to 1.0 mg/L and 0.25 mg/L MFA, respectively. In early life stage exposure using D. rerio, significant decrease of larval survival was observed at 1 mg/L. Changes in vitellogenin (VTG) protein concentrations in 32 day post fertilization fish and vtgI mRNA expression in adult male fish suggest endocrine disruption potentials of MFA. Among the genes of hypothalamus-pituitary-gonad axis, transcriptions of gnrh, gnrhr, cyp19a, and cyp19b increased, supporting estrogenic potential of MFA. Along with histological changes in ovaries, the results of this study provide evidences of endocrine disruption capacity of MFA. However, the effective concentrations are orders of magnitude greater than those occurring in the ambient aquatic environment.

Study the antiviral activity of some derivatives of tetracycline and non-steroid anti inflammatory drugs towards dengue virus.

Various clinical symptoms are caused by dengue virus ranging from mild fever to severe hemorrhagic fever while there is no successful anti-dengue therapeutics available. Among different strategies towards identifying and developing anti-dengue therapeutics, testing anti-dengue properties of known drugs could represent an efficient strategy for which information of its medical approval, toxicity and side effects is readily available. In this study, we evaluated the antiviral activity of some medical compounds towards dengue NS2B-NS3 protease (DENV2 NS2B-NS3pro) as a target to inhibit dengue virus replication. Mefenamic acid, a non-steroid anti inflammatory drug and doxycycline, a derivative antibiotic of tetracycline both showed significant inhibition potential against DENV2 NS2B-NS3pro Ki values 32 ± 2 µM and 55 ± 5 µM respectively. The effective cytotoxic concentrations of 50% (CC50) against Vero cells were evaluated for mefenamic acid (150 ± 5 µM) and doxycycline (125 ± 4 µM). Concentrations lower than CC50 were used to test the inhibition potential of these compounds against DENV2 replication in Vero cells. The results showed significant reduction in viral load after applying mefenamic acid and doxycyline in concentration dependent manner. Mefenamic acid reduced viral RNA at EC50 of 32 ± 4 µM whilst doxycycline EC50 was 40 ± 3 µM. Mefenamic acid showed higher selectivity against dengue virus replication in vitro compared to doxycycline. These findings underline the need for further experimental and clinical studies on these drugs utilizing its anti-dengue and anti-inflammatory activities to attenuate the clinical symptoms of dengue infection.

Spatial metabolic fingerprinting using FT-IR spectroscopy: investigating abiotic stresses on Micrasterias hardyi.

The release of active pharmaceutical ingredients (APIs) into the environment is an ecologically important topic for study because, whilst APIs have been designed to have a wide range of biological properties for the target of interest (usually in man), little information on potential ecological risks is currently available regarding their effects on the organisms that inhabit the environment. In this study, the algae Micrasterias hardyi was exposed to propranolol, metoprolol (beta-adrenergic receptor agonist drugs) and mefenamic acid (a non steroidal anti-inflammatory drug), at concentrations ranging between 0.002-0.2 mM. Initial studies showed that Fourier transform infrared (FT-IR) spectroscopy on algal homogenates illustrated that all three APIs had a quantitative effect on the metabolism of the organisms and it was possible to estimate the level of API exposure from the FT-IR metabolic fingerprints using partial least squares (PLS) regression. From the inspection of the PLS loadings matrices it was possible to elucidate that all drugs caused effects on protein and lipid levels. Most strikingly propranolol had significant effects on the lipid components of the cell. These were dramatically reduced possibly as a consequence of loss of membrane integrity. In order to investigate this further, FT-IR microspectroscopy was used to generate detailed metabolic fingerprinting maps. These chemical maps revealed that all the drugs had a dramatic effect on the distribution of various chemical species throughout the algae, and that all drugs had an affect on protein and lipid levels. In particular, as noted in the PLS analyses for propranolol treated cells, the lipid complement found in the lipid storage areas in the processes of M. hardyi was greatly reduced. This illustrates the power of spatial metabolic fingerprinting for investigating abiotic stresses on complex biological species.

A comparative histological study of alginate beads as a promising controlled release delivery for mefenamic acid.

The new mefenamic acid-alginate bead formulation prepared by ionotropic gelation method using 3 x 2(2) factorial design has shown adequate controlled release properties in vitro. In the present study, the irritation effects of mefenamic acid (MA), a prominent non-steroidal anti-inflammatory (NSAI) drug, were evaluated on rat gastric and duodenal mucosa when suspended in 0.5% (w/v) sodiumcarboxymethylcellulose (NaCMC) solution and loaded in alginate beads. Wistar albino rats weighing 200 +/- 50 g were used during in vivo animal studies. In this work, biodegradable controlled release MA beads and free MA were evaluated according to the degree of gastric or duodenal damage following oral administration in rats. The gastric and duodenal mucosa was examined for any haemorrhagic changes. Formulation code A10 showing both Case II transport and zero order drug release and t(50) % value of 5.22 h was chosen for in vivo animal studies. For in vivo trials, free MA (100 mgkg(-1)), blank and MA (100 mgkg(-1)) loaded alginate beads (formulation code A10) were suspended in 0.5% (w/v) NaCMC solution and each group was given to six rats orally by gavage. NaCMC solution was used as a control in experimental studies. In vivo data showed that the administration of MA in alginate beads prevented the gastric lesions.

Mefenamic acid bi-directionally modulates the transient outward K+ current in rat cerebellar granule cells.

The effect of non-steroidal anti-inflammatory drugs (NSAIDs) on ion channels has been widely studied in several cell models, but less is known about their modulatory mechanisms. In this report, the effect of mefenamic acid on voltage-activated transient outward K(+) current (I(A)) in cultured rat cerebellar granule cells was investigated. At a concentration of 5 microM to 100 microM, mefenamic acid reversibly inhibited I(A) in a dose-dependent manner. However, mefenamic acid at a concentration of 1 microM significantly increased the amplitude of I(A) to 113+/-1.5% of the control. At more than 10 microM, mefenamic acid inhibited the amplitude of I(A) without any effect on activation or inactivation. In addition, a higher concentration of mefenamic acid induced a significant acceleration of recovery from inactivation with an increase of the peak amplitude elicited by the second test pulse. Intracellular application of mefenamic acid could significantly increase the amplitude of I(A), but had no effect on the inhibition induced by extracellular mefenamic acid, implying that mefenamic acid may exert its effect from both inside and outside the ion channel. Furthermore, the activation of current induced by intracellular application of mefenamic acid was mimicked by other cyclooxygenase inhibitors and arachidonic acid. Our data demonstrate that mefenamic acid is able to bi-directionally modulate I(A) channels in neurons at different concentrations and by different methods of application, and two different mechanisms may be involved.

Altered brain penetration of diclofenac and mefenamic acid, but not acetaminophen, in Shiga-like toxin II-treated mice.

It is well accepted that bacterial and virus infections elevate the levels of cytokines in serum and cerebrospinal fluids. Such high levels of cytokines might alter the integrity of the blood-brain barrier (BBB) and/or blood-cerebrospinal fluid barrier (BCSFB), subsequently affecting brain penetration of drugs. However, few reports have addressed this issue. Thus, we investigated brain penetration of cyclooxygenase (COX) inhibitors, commonly used as antipyretics, in mice treated with Shiga-like toxin II (SLT-II) derived from E. coli O157:H7, which significantly elevates cytokine levels. As antipyretics, we used diclofenac, mefenamic acid, and acetaminophen. We found that SLT-II significantly increased the brain-to-plasma concentration ratio (Kp) of diclofenac and mefenamic acid, but not of acetaminophen. Moreover, the Kp of diclofenac and mefenamic acid was increased by probenecid, an anionic compound. These results suggest that efflux anion transporters might be involved in the transport of diclofenac and mefenamic acid. Western blot analysis revealed that SLT-II decreased the expression of organic anion transporter-3, an efflux transporter located on the BBB and/or BCSFB. Taken together, these results suggest that SLT-II and/or SLT-II-stimulated cytokines might change brain penetration of drugs and could possibly increase the risk of their side-effects by altering the expression of transporters.

The effects of mefenamic acid on the osmotic fragility of lacertilian erythrocytes.

Osmotic fragility of red cells is increased by the use of mefenamic acid. The use of this analgesic induces hemolytic anemia. Study of osmotic fragility of RBCs of control and test was observed following administration of 7.1 mg, 10.5 mg and 14 mg/day mefenamic acid to each lizard. Increased osmotic fragility was observed with increase in the amount of dose on day 6 and day 12.

[Acute renal failure--"a well meant present from a friend"]. / Akutes Nierenversagen--"ein Geschenk einer Freundin".

Acute allergic interstitial nephritis (AIN) due to non-steroidal anti-inflammatory drugs (NSAID) is a well known but rare adverse drug event. Here, we describe the case of a 70 year old woman with recurrent episodes of acute renal failure. A first episode of (AIN) occurred after the intake of mefenaminic acid tablets. A second episode of AIN occurred two years later, this time after transdermal application of diclofenac. Our case illustrates cross-reactivity between NSAIDs and shows that transdermally applied medication can cause systemic adverse events as well. Patients do not mention ointments because they often do not realize that ointments contain active substances, and physicians forget to ask.

Actions of mefenamic acid on pregnant albino rats

Misuse and abuse of the non-steroidal anti-inflammatory and analgesic mefenamic acid among pregnant women in developing coutries constitute a matter of medical concern, mainly as a function of the potentially serious side effects of that drug, notably at the digestive system level. Female rats were treated during the entire pregnancy period (from day 0 up to day 20) with 5, 15, or 45 mg/kg of mefenamic acid (MA) once daily, by gavage. Controls received the drug vehicle. We observed that there was a slight yet significant impairment of maternal body weight gain of the animals treated with the two highest doses of MA. Although the drug was proven to exert deleterious effects on kidney and liver metabolic functions, no gross signs of renal or hepatic toxicity were detected in our animals and in their concepts. The digestive effects would be presumably caused by the inhibitory actions of MA on the luminal fluid movement and are accounted for by the observed body weight loss during pregnancy.

Influence of nonsteroidal anti-inflammatory drugs on calcium efflux in isolated rat renal cortex mitochondria and aspects of the mechanisms involved.

In the present study we investigated the influence of several nonsteroidal anti-inflammatory drugs on calcium efflux in isolated rat renal cortex mitochondria in order to assess their potential to disrupt cell calcium homeostasis, as well as aspects of the mechanisms associated with oxidation of mitochondrial pyridine nucleotides (NAD(P)H) and with inhibition of the process by cyclosporin A (CsA). Calcium efflux was estimated with arsenazo III as an indicator and the redox state of NAD(P)H was monitored fluorimetrically at the 366/450 nm excitation/emission wavelength pair. Dipyrone, paracetamol and ibuprofen did not induce calcium efflux even at 1 mM, piroxicam and salicylate were poor inducers, while diclofenac sodium and mefenamic acid were potent inducers releasing calcium even at 20 microM and 10 microM, respectively. In the presence of 10 microM calcium, CsA had no appreciable effect while in the presence of 30 microM calcium it delayed calcium efflux. Oxidation of mitochondrial NAD(P)H, concomitant with calcium efflux and inhibited by CsA, was observed only in the presence of 30 microM calcium. The results suggest that diclofenac sodium and mefenamic acid induce calcium efflux in mitochondria through both a mechanism intrinsic to the mitochondrial membrane permeability transition and a mechanism including the electroneutral Ca2+/nH+ porter.

Caffeine potentiation of mefenamic acid-induced lesions in the rat renal medulla.

The effect of caffeine given in combination with mefenamic acid on the renal medulla was examined. Sprague-Dawley rats were divided into four groups and gavage fed either vehicle suspension (control), mefenamic acid, mefenamic acid+caffeine or caffeine only for 4 months. Renal tissue taken from the corticomedullary junction was processed for electron microscopy. Ultrathin sections were cut after identification of vasa rectae on survey sections. On subsequent morphometric analysis, percentage interstitial tissue was calculated from the total area of vasa recta less the non-interstitial tissue. The median percentage of interstitial tissue in the mefenamic acid and caffeine group was 41 (range 33-50; n = 15) compared with 34 (20-48; n = 20) in mefenamic acid (P less than 0.01), 29 (15-42; n = 15) in caffeine only (P less than 0.001) and 32 (20-46; n = 18) in vehicle-treated animals (P less than 0.001). There were no significant differences between mefenamic acid alone and vehicle or caffeine-only groups or between caffeine-only and vehicle-treated controls. This suggests that caffeine potentiates the effect of the non-steroidal anti-inflammatory drug, mefenamic acid, on the rat renal medulla, resulting in a quantitative increase in the interstitial tissue between adjacent afferent and efferent vasa recta.

Experimental renal papillary necrosis in the Syrian hamster.

These studies evaluate the susceptibility of the Syrian hamster to the induction of renal papillary lesions after exposure to 2-bromethylamine (2-BEA), mefenamic acid, indomethacin, acetaminophen and phenylbutazone. In most cases there were 25 animals per dose group. Papillary necrosis was produced by single or multiple ip doses of 75 mg 2-BEA/kg and above, and was present within 12 hr of administration of a dose of 500 mg/kg body weight. There were lesions in the renal papilla of hamsters 10 days after a single dose of 500 mg 2-BEA/kg. The severity of papillary lesions increased up to 4 days after exposure in hamsters given a single dose of either 250 or 500 mg 2-BEA/kg. The severity of papillary lesions did not increase with the number of doses in hamsters given multiple doses (2-5) of 100 mg 2-BEA/kg. Renal papillary necrosis was observed in about 40% of hamsters given 100, 200 or 400 mg mefenamic acid/kg. Only a few of the hamsters given indomethacin had renal papillary lesions and none of those given acetaminophen (up to 400 mg/kg) or phenylbutazone (up to 600 mg/kg) developed renal papillary lesions.