Potentiation of large conductance KCa channels by niflumic, flufenamic, and mefenamic acids.

Large conductance calcium-activated K+ (KCa) channels are rapidly activated by niflumic acid dose-dependently and reversibly. External niflumic acid was about 5 times more potent than internal niflumic acid, and its action was characterized by an increase in the channel affinity for [Ca2+], a parallel left shift of the voltage-activation curve, and a decrease of the channel long-closed states. Niflumic acid applied from the external side did not interfere with channel block by charybdotoxin, suggesting that its site of action is not at or near the charybdotoxin receptor. Accordingly, partial tetraethylammonium blockade did not interfere with channel activation by niflumic acid. Flufenamic acid and mefenamic acid also stimulated KCa channel activity and, as niflumic acid, they were more potent from the external than from the internal side. Fenamates applied from the external side displayed the following potency sequence: flufenamic acid approximately niflumic acid >> mefenamic acid. These results indicate that KCa channels possess at least one fenamatereceptor whose occupancy leads to channel opening.     

Inhibition of Gap Junction Hemichannels by Chloride Channel Blockers

Electrophysiological methods were used to assess the effect of chloride-channel blockers on the macroscopic and microscopic currents of mouse connexin50 (Cx50) and rat connexin46 (Cx46) hemichannels expressed in Xenopus laevis oocytes. Oocytes were voltage-clamped at -50 mV and hemichannel currents (ICx50 or ICx46) were activated by lowering the extracellular Ca2+ concentration ([Ca2+]o) from 5 mM to 10 microM. Ion-replacement experiments suggested that ICx50 is carried primarily (>95%) by monovalent cations (PK : PNa : PCl = 1.0 : 0.74 : 0.05). ICx50 was inhibited by 18beta-glycyrrhetinic acid (apparent Ki, 2 microM), gadolinium (3 microM), flufenamic acid (3 microM), niflumic acid (11 microM), NPPB (15 microM), diphenyl-2-carboxylate (26 microM), and octanol (177 microM). With the exception of octanol, niflumic acid, and diphenyl-2-carboxylate, the above agents also inhibited ICx46. Anthracene-9-carboxylate, furosemide, DIDS, SITS, IAA-94, and tamoxifen had no inhibitory effect on either ICx50 or ICx46. The kinetics of ICx50 inhibition were not altered at widely different [Ca2+]o (10-500 microM), suggesting that drug-hemichannel interaction does not involve the Ca2+ binding site. In excised membrane patches, application of flufenamic acid or octanol to the extracellular surface of Cx50 hemichannels reduced single channel-open probability without altering the single-channel conductance, but application to the cytoplasmic surface had no effect on the channels. We conclude that some chloride-channel blockers inhibit lens-connexin hemichannels by acting on a site accessible only from the extracellular space, and that drug-hemichannel interaction involves a high-affinity site other than the Ca2+ binding site.     

Modulation of Glutamate and Glycine Transporters by Niflumic,Flufenamic and Mefenamic Acids

Three fenamates—niflumic, flufenamic and mefenamic acids—were tested for effects on substrate-induced currents of glutamate and glycine transporters (EAAT1, EAAT2, GLYT1b and GLYT2a) expressed in Xenopus laevis oocytes. All fenamates inhibited EAAT1 currents; 100 μM flufenamic acid produced the most inhibition, decreasing the I _max by 53 ± 4% (P < 0.001). EAAT2 currents were less sensitive, but 100 μM flufenamic acid inhibited the I _max by 34 ± 5% (P = 0.006). All fenamates inhibited GLYT1b currents; 100 μM flufenamic acid produced the most inhibition, decreasing the I _max by 61 ± 1% (P < 0.001). At 100 μM, effects on the GLYT2a I _max were mixed: 13 ± 2% inhibition by flufenamic acid (P = 0.002), 30 ± 6% enhancement by niflumic acid (P = 0.002), and no effect by mefenamic acid. Minor effects on substrate affinity suggested non-competitive mechanisms. These data could contribute to the development of selective transport modulators.     

Inactivation of creatine kinase during the interaction of mefenamic acid with horseradish peroxidase and hydrogen peroxide: participation by the mefenamic acid radical

Creatine kinase (CK) was used as a marker molecule to examine the side effects of damage to tissues by mefenamic acid, an effective drug to treat rheumatic and arthritic diseases, with horseradish peroxidase and hydrogen peroxide (HRP-H(2)O(2)). Mefenamic acid inactivated CK during its interaction with HRP-H(2)O(2). Also, diphenylamine and flufenamic acid caused a loss of CK activity, indicating the imino group, not substituent groups, in the phenyl rings have a crucial role in CK inactivation. Rapid change in mefenamic acid spectra was detected, suggesting that mefenamic acid is efficiently oxidized by HRP-H(2)O(2). Peroxidases oxidize xenobiotics to free radicals by a one-electron transfer. However, direct detection of mefenamic acid radicals by electron spin resonance (ESR) was unsuccessful. Reduced glutathione and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) in the reaction mixture containing mefenamic acid with HRP-H(2)O(2) produced ESR signals consistent with a DMPO-glutathionyl radical adduct. These results suggest that inactivation of CK is probably caused through formation of mefenamic acid radicals. Sulfhydryl groups and tryptophan residues of CK were diminished by mefenamic acid with HRP-H(2)O(2). Other SH enzymes, including alcohol dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase, were very sensitive to mefenamic acid with HRP-H(2)O(2). Inactivation of SH enzymes may explain some deleterious actions of mefenamic acid.     

Alpha-adrenergic stimulation activates a calcium-sensitive chloride current in brown fat cells

The first response of brown adipocytes to adrenergic stimulation is a rapid depolarizing conductance increase mediated by alpha-adrenergic receptors. We used patch recording techniques on cultured brown fat cells from neonatal rats to characterize this conductance. Measurements in perforated patch clamped cells showed that fast depolarizing responses were frequent in cells maintained in culture for 1 d or less, but were seen less often in cells cultured for longer periods. Ion substitution showed that the depolarization was due to a selective increase in membrane chloride permeability. The reversal potential for the depolarizing current in perforated patch clamped cells indicated that intracellular chloride concentrations were significantly higher than expected if chloride were passively distributed. The chloride conductance could be activated by increases in intracellular calcium, either by exposing intact cells to the ionophore A23187 or by using pipette solutions with free calcium levels of 0.2-1.0 microM in whole- cell configuration. The chloride conductance did not increase monotonically with increases in intracellular calcium, and going whole cell with pipette-free calcium concentrations > or = 10 microM rapidly inactivated the current. The chloride currents ran down in whole-cell recordings using intracellular solutions of various compositions, and were absent in excised patches. These findings imply that cytoplasmic factors in addition to intracellular calcium are involved in regulation of the chloride conductance. The chloride currents could be blocked by niflumic acid or flufenamic acid with IC50s of 3 and 7 microM, or by higher concentrations of SITS (IC50 = 170 microM), DIDS (IC50 = 50 microM), or 9-anthracene carboxylic acid (IC50 = 80 microM). The chloride conductance activated in whole cell by intracellular calcium had the permeability sequence PNOS > PI > PBr > PCl >> Paspartate, measured from either reversal potentials or conductances. Instantaneous current-voltage relations for the calcium-activated chloride currents were linear in symmetric chloride solutions. Much of the current was time and voltage independent and active at all membrane potentials between -100 and +100 mV, but an additional component of variable amplitude showed time-dependent activation with depolarization. Volume- sensitive chloride currents were also present in brown fat cells, but differed from the calcium-activated currents in that they responded to cell swelling, required intracellular ATP in whole-cell recordings, showed no sensitivity to intracellular or extracellular calcium levels, and were relatively resistant to block by niflumic and flufenamic acids. (ABSTRACT TRUNCATED AT 400 WORDS)     

Direct block of the cystic fibrosis transmembrane conductance regulator Cl(-) channel by niflumic acid

Niflumic acid is widely used to inhibit Ca(2+) -activated Cl(-) channels. However, the chemical structure of niflumic acid resembles that of diphenylamine-2-carboxylate, a drug that inhibits the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel. To investigate how niflumic acid inhibits CFTR Cl(-) channel, we studied recombinant wild-type human CFTR in excised inside-out membrane patches. When added to the intracellular solution, niflumic acid caused a concentration- and voltage-dependent decrease of CFTR Cl(-) current with half-maximal inhibitory concentration (K(i)) of 253 microM and Hill co-efficient of approximately 1, at -50 mV. Niflumic acid inhibition of single CFTR Cl(-) channels was characterized by a very fast, flickery block that decreased dramatically current amplitude without altering open-probability. Consistent with these data, spectral analysis of CFTR Cl(-) currents suggested that channel block by niflumic acid was described by the closed <--> open <--> blocked kinetic scheme with blocker on rate (k(on)) = 13.9 x 10(6) M(-1)s(-1), off rate (k(off))=3348 s(-1) and dissociation constant (K(d)) = 241 microM, at -50 mV. Based on these data, we tested the effects of niflumic acid on transepithelial Cl(-) secretion and cyst growth using type I MDCK epithelial cells. Niflumic acid (200 microM) inhibited cAMP-stimulated, bumetanide-sensitive short-circuit current by 55%. Moreover, the drug potently retarded cyst growth. We conclude that niflumic acid is an open-channel blocker of CFTR that inhibits Cl(-) permeation by plugging the channel pore. It or related agents might be of value in the development of new therapies for autosomal dominant polycystic kidney disease.     

Selective inhibition of Cl(-) conductance in toad skin by blockers of Cl(-) channels and transporters

We compared the effects exerted by two classes of Cl(-) transport inhibitors on a Cl(-)-selective, passive anion transport route across the skin of Bufo viridis, the conductance (G(Cl)) of which can be activated by transepithelial voltage perturbation or high cAMP at short circuit. Inhibitors of antiporters (erythrosine, eosin) or cotransporters (furosemide) reduced voltage-activated G(Cl) with IC(50) of 6 +/- 1, 54 +/- 12, and 607 +/- 125 microM, respectively; they had no effect on the cAMP-induced G(Cl). The voltage for half-maximal activation of G(Cl) (V(50)) increased compared with controls, but effects on the maximal G(Cl) at more positive clamp potentials were small. Cl(-) channel blockers from the diphenylamino-2-carboxylic acid (DPC) family [dichloro-DPC, niflumic acid, flufenamic acid, and 5-nitro-2-(3-phenylpropylamino)benzoic acid] reduced the voltage-activated G(Cl) with IC(50) of 8.3 +/- 1.2, 10.5 +/- 0.6, 16.5 +/- 3.4, and 36.5 +/- 11.4 microM, respectively, and also inhibited the cAMP-induced G(Cl), albeit with slightly larger IC(50). V(50) was not significantly changed compared with controls; the maximal G(Cl) was strongly reduced. We conclude that the pathway for Cl(-) is composed of the conductive pore proper, which is blocked by the derivatives of DPC, and a separate, voltage-sensitive regulator, which is influenced by blockers of cotransporters or antiporters. This influence is partly overcome by increasing the clamp potential and removed by high concentrations of cAMP, which renders the pathway insensitive to voltage.     

Dose-dependent potentiation and inhibition of single Ca2+-activated K+ channels by flufenamic acid

Using the patch-clamp technique in an inside-out configuration, we studied the action of an antiinflammatory drug, flufenamic acid (FFA), on single large-conductance Ca2+-activated K+ channels in cultured Vero kidney cells. Depending on its concentration, FFA caused either potentiation or inhibition of K(Ca) channel activity of the same channel. Within the concentration ranges of about 5 to 10 microM and of 50 to 500 microM, FFA increased the channel activity; and within the intermediate range of about 10 to 50 microM, FFA inhibited the channels. The effects were only partially reversible. The activating phases were accompanied by an increase in the channel open time and decreases in the channel closed time and slope factor of the Ca2+ concentration-response curve. An apparent dissociation constant of Ca2+ interaction with the channel changed slightly. Possible mechanisms of the FFA effects are discussed.     

Acidic nonsteroidal anti-inflammatory drugs inhibit rat brain fatty acid amide hydrolase in a pH-dependent manner

Previous studies have demonstrated that fatty acid amide hydrolase, the enzyme responsible for the metabolism of anandamide, is inhibited by the acidic non-steroidal anti-inflammatory drug (NSAID) ibuprofen with a potency that increases as the assay pH is reduced. Here we show that (R)-, (S)- and (R,S)-flurbiprofen, indomethacin and niflumic acid show similar pH-dependent shifts in potency to that seen with ibuprofen. Thus, (S)-flurbiprofen inhibited 2 microM [3H]anandamide metabolism with IC50 values of 13 and 50 microM at assay pH values of 6 and 8, respectively. In contrast, the neutral compound celecoxib was a weak fatty acid amide hydrolase inhibitor and showed no pH dependency (IC50 values approximately 300 microM at both assay pH). The cyclooxygenase-2-selective inhibitors nimesulide and SC-58125 did not inhibit fatty acid amide hydrolase activity at either pH. The data are consistent with the conclusion that the non-ionised forms of the acidic NSAIDs are responsible for the inhibition of fatty acid amide hydrolase.     

Relationship of inhibition of prostaglandin biosynthesis by analgesics to asthma attacks in aspirin-sensitive patients.

Eleven patients with asthma and aspirin hypersensitivity have been challenged with eight non-steroidal anti-inflammatory drugs. Each drug was given by mouth in at least three different doses and the patients'' symptoms and peak expiratory flow (PEF) rates were observed over a three-hour period. Indomethacin 5 mg caused bronchoconstriction in all patients. Therapeutic doses of mefenamic or flufenamic acid caused bronchoconstriction in most patients. Phenylbutazone 200-400 mg induced a moderate fall in PEF. There were no reactions to therapeutic doses of salicylamide, paracetamol, benzydamine, and chloroquine. Microsomal prostaglandin synthetase, activity was inhibited by aspirin, indomethacin, mefenamic acid, flufenamic acid, and phenylbutazone. The other four drugs had no inhibitory effect. We suggest that precipitation of attacks in asthmatic patients hypersensitive to certain anti-inflammatory drugs is related to drug''s ability to inhibit prostaglandin biosynthesis.     

Liquid chromatography method for determination of mefenamic acid in human serum

A simple, rapid and specific method for analysis of mefenamic acid (I) in serum by a sensitive high-performance liquid chromatography is described. Only 70 microl of serum and a little sample work-up is required. A simple procedure of extraction by dichloromethane followed by evaporation to dryness under gentle stream of nitrogen and dissolving the dried residue in mobile phase was used. The mefenamic acid peak was separated from endogenous peaks on a C(8) column by a mobile phase of acetonitrile-water (50:50, v/v, pH 3). Mefenamic acid and internal standard (IS) (diclofenac) were eluted at 7.4 and 5.4 min, respectively. The limit of quantitation of mefenamic acid in serum was 25 ng/ml at 280 nm. The method was linear over the range of 25-2000 ng/ml with r(2) of 0.998. Mean recovery for mefenamic acid was 110%.     

Use of niflumic acid to determine the nature of the asymmetry of the human erythrocyte anion exchange system

Niflumic acid is a noncompetitive inhibitor of chloride exchange, which binds to a site different from the transport or modifier sites. When the internal Cl- concentration is raised, at constant extracellular Cl- , the inhibitory potency of niflumic acid increases. This effect cannot be attributed to changes in membrane potential, but rather it suggests that niflumic acid binds to the anion exchange protein band 3 only when the transport site faces outward. When the chloride gradient is reversed, with Clo greater than Cli , the inhibitory potency of niflumic acid decreases greatly, which indicates that the affinity of niflumic acid for band 3 with the transport site facing inward is almost 50 times less than when the transport site faces outward. Experiments in which Cli = Clo show no significant change in the inhibition by niflumic acid when Cl- is lowered from 150 to 10 mM. These data suggest that the intrinsic dissociation constants for Cl- at the two sides of the membrane are nearly equal. Thus, the chloride- loaded transport sites have an asymmetric orientation like that of the unloaded transport sites, with approximately 15 times more sites facing the inside than the outside. The asymmetry reflects an approximately 1.5 kcal/mol free energy difference between the inward-facing and outward-facing chloride-loaded forms of band 3. High concentrations of chloride (with Cli = Clo), which partially saturate the modifier site, have no effect on niflumic acid inhibition, which indicates that chloride binds equally well to the modifier site regardless of the orientation of the transport site.     

Nonsteroidal anti-inflammatory drugs and their analogues as inhibitors of aldo-keto reductase AKR1C3: new lead compounds for the development of anticancer agents

Nonsteroidal anti-inflammatory drugs (NSAIDs) like indomethacin, flufenamic acid, and related compounds have been recently identified as potent inhibitors of AKR1C3. We report that some other NSAIDs (diclofenac and naproxen) also inhibit AKR1C3, with the IC(50) values in the low micromolar range. In order to obtain more information about the structure-activity relationship and to identify new leads, a series of compounds designed on the basis of NSAIDs were synthesized and screened on AKR1C3. The most active compounds were 2-[(2,2-diphenylacetyl)amino]benzoic acid 4 (IC(50)=11microM) and 3-phenoxybenzoic acid 10 (IC(50)=0.68microM). These compounds represent promising starting points for the development of new anticancer agents.     

Inhibition study of rabbit liver cytosolic reductases involved in daunorubicin toxication

Anthracycline cardiotoxicity represents the most unfavorable side effect of these highly efficient anticancer drugs. Several biotransformation enzymes have been described to contribute to their cardiotoxicity. Besides the activities of CYP450 isoforms which lead to the generation of reactive oxygen species (ROS), the cytosolic reductases have attracted attention nowadays. The reductases known to metabolize anthracyclines to C13-hydroxyanthracyclines are carbonyl reductase (CR, 1.1.1.184) and the aldo-keto reductases (AKR1C2, 1.3.1.20; AKR1A1, 1.1.1.2). Their participation in the formation of the toxic C13-hydroxymetabolite has been investigated in rabbit using diagnostic inhibitors of CR and AKR1C2. The kinetics and the type of reductase inhibition exerted by the two inhibitors have been described and it was found that CR was the main daunorubicin reductase at both optimal and physiological pH with the kinetic parameters for daunorubicin reduction of Km = 17.01 +/- 1.98 microM and V(max) = 139.60 +/- 5.64 pcat/mg. The IC50 values for quercitrin and flufenamic acid were 5.45 +/- 1.37 microM and 3.68 +/- 1.58 microM, respectively. The inhibition was uncompetitive for both inhibitors and irreversible in the case of flufenamic acid.     

Anti-oxidant, in vitro, in vivo anti-inflammatory activity and antiproliferative activity of mefenamic acid and its metal complexes with manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II)

Some new complexes of mefenamic acid with potentially interesting biological activity are described. The complexes of mefenamic acid [Mn(mef)(2)(H(2)O)(2)], 1, [Co(mef)(2)(H(2)O)(2)], 2, [Ni(mef)(2)(H(2)O)(2)], 3, [Cu(mef)(2)(H(2)O)](2), 4 and [Zn(mef)(2)], 5, were prepared by the reaction of mefenamic acid, a potent anti-inflammatory drug with metal salts. Optical and infrared spectral data of these new complexes are reported. Monomeric six-coordinated species were isolated in the solid state for Mn(II), Ni(II) and Co(II), dimeric five-coordinated for Cu(II) and monomeric four-coordinated for Zn(II). In DMF or CHCl(3) solution the coordination number is retained and the coordinated molecules of water are replaced by solvent molecules. The anti-oxidant properties of the complexes were evaluated using the 1,1-diphenyl-2-picrylhydrazyl, DPPH, free radical scavenging assay. The scavenging activities of the complexes were measured and compared with those of the free drug and vitamin C. We have explored their ability to inhibit soybean lipoxygenase, beta-glucuronidase and trypsin- induced proteolysis. The complex [Mn(mef)(2)(H(2)O)(2)] exhibits the highest antioxidant activity and the highest inhibitory effect against the soybean lipogygenase (LOX), properties that are not demonstrated by mefenamic acid. Their inhibitory effects on rat paw edema induced by Carrageenan was studied and compared with those of mefenamic acid. The complex [Zn(mef)(2)] exhibited a strong inhibitory effect at 0.1 mmol/Kg B.W. (81.5 +/- 1.3% inhibition), superior to the inhibition induced by mefenamic acid at the same dose (61.5 +/- 2.3% inhibition). Mefenamic acid and its metal complexes have been evaluated for antiproliferative activity in vitro against the cells of three human cancer cell lines: MCF-7 (human breast cancer cell line), T24 (bladder cancer cell line), A-549 (non-small cell lung carcinoma) and a mouse fibroblast L-929 cell line. The copper(II) complex displays against T24, MCF-7 and L-929 cancer cell lines, IC(50) values in a microM range similar to that of the antitumor drug cis-platin and they are considered for further stages of screening in vitro and/or in vivo as agents with potential antitumor activity.     

Cl- channel blockers NPPB and niflumic acid blunt Ca(2+)-induced erythrocyte 'apoptosis'.

Exposure to Ca2+ ionophore ionomycin, osmotic shock, oxidative stress and glucose depletion trigger cell shrinkage and scramblase-mediated phosphatidylserine exposure at the outer leaflet of the erythrocyte cell membrane. The effects are partially due to activation of GARDOS channels and subsequent cellular K+ loss leading not only to cell shrinkage but also participating in the triggering of erythrocyte scramblase. As conductive loss of K+ would depend on the parallel loss of anions we hypothesised that activation of scramblase is similarly dependent on the activity of Cl- channels. To test this hypothesis, we used Cl- channel blockers NPPB and niflumic acid. It is shown here that treatment of erythrocytes with 1 microM ionomycin leads to cellular K+ loss, decrease of hematocrit and decrease of forward scatter in FACS analysis reflecting cell shrinkage as well as increase of annexin positive cells reflecting phosphatidylserine exposure. Those events were significantly blunted in the presence of 100 microM NPPB by 34% (K+ loss), 45% (hematocrit), 32% (forward scatter) and 69% (annexin binding), or in the presence of 100 microM niflumic acid by 15% (forward scatter) and 45% (annexin binding), respectively. Moreover, oxidative stress triggered annexin binding which was again significantly inhibited (by 51%) in the presence of 100 microM NPPB. In conclusion, Cl- channels presumably participate in the regulation of erythrocyte 'apoptosis'.     

Inhibition of anion permeability by amphiphilic compounds in human red cell: Evidence for an interaction of niflumic acid with the band 3 protein

Summary In human erythrocyte, permeability to the anion is instantaneously, reversibly, and noncompetitively inhibited by the nonsteroidal anti-inflammatory drug, niflumic acid. The active form of this powerful inhibitor (I ₅₀=6×10^–7 m) is the ionic form. We demonstrated that: (i) The binding of niflumic acid to the membrane of unsealed ghosts shows one saturable and one linear component over the concentration range studied. The saturable component vanishes when chloride transport is fully inhibited by covalently bound 4-acetamido-4-isothiocyano stilbene-2,2-disulfonic acid (SITS). Our estimate of these SITS protectable niflumate binding sites (about 9×10⁵ per cell) agrees with the number of protein molecules per cell in band 3. These sites are halfsaturated with 10^–6 m niflumic acid, a concentration very close toI ₅₀. (ii) Niflumic acid inhibits the binding reaction of SITS with anion controlling transport sites. These results indicate that niflumic acid and SITS are mutually exclusive inhibitors, suggesting that niflumic acid interacts with the protein in band 3.Niflumic acid also decreases glucose and ouabain-insensitive sodium permeabilities. However, these effects are produced at a very high concentration of niflumic acid (in millimolar range), suggesting unspecific action, possibly through lipid phase.     

Cyclic nucleotide signaling mediates an odorant-suppressible chloride conductance in lobster olfactory receptor neurons

We have previously shown that lobster olfactory receptor neurons (ORNs) express an odorant-suppressible Cl(-) conductance that modulates the output of the cells. Here, we develop a more complete pharmacological profile of this conductance, showing it is blockable by the Cl(-) channel blockers DIDS, 9-AC and flufenamic acid, but not by niflumic acid. We then show that a conductance with this pharmacological profile is mediated by cyclic nucleotide signaling. These findings further our understanding of the cellular mechanisms through which odorants can modulate the output of lobster ORNs.     

10-Thiastearic acid inhibits both dihydrosterculic acid biosynthesis and growth of the protozoan Crithidia fasciculata

10-Thiastearic acid is a specific inhibitor of the biosynthesis of dihydrosterculic acid (9,10-methyleneoctadecanoic acid) in the trypanosomatid protozoan Crithidia fasciculata. A 50% inhibition of the biosynthesis of dihydrosterculate is observed in the presence of 4 microM 10-thiastearate in the protozoan growth medium, but little effect is seen on the distribution of the other fatty acids. In addition, the growth of the protozoa is slowed by the presence of 10-thiastearate, with 50% growth inhibition produced at about 10 microM. A possible mechanism of this inhibition and the implication of this result with regard to the design of antiprotozoal agents are discussed.     

Treatment of menorrhagia during menstruation: randomised controlled trial of ethamsylate,mefenamic acid,and tranexamic acid.

OBJECTIVE: To compare the efficacy and acceptability of ethamsylate, mefenamic acid, and tranexamic acid for treating menorrhagia. DESIGN: Randomised controlled trial. SETTING: A university department of obstetrics and gynaecology. SUBJECTS: 76 women with dysfunctional uterine bleeding. INTERVENTIONS: Treatment for five days from day 1 of menses during three consecutive menstrual periods. 27 patients were randomised to take ethamsylate 500 mg six hourly, 23 patients to take mefenamic acid 500 mg eight hourly, and 26 patients to take tranexamic acid 1 g six hourly. MAIN OUTCOMES MEASURES: Menstrual loss measured by the alkaline haematin method in three control menstrual periods and three menstrual periods during treatment; duration of bleeding; patient''s estimation of blood loss; sanitary towel usage; the occurrence of dysmenorrhoea; and unwanted events. RESULTS: Ethamsylate did not reduce mean menstrual blood loss whereas mefenamic acid reduced blood loss by 20% (mean blood loss 186 ml before treatment, 148 ml during treatment) and tranexamic acid reduced blood loss by 54% (mean blood loss 164 ml before treatment, 75 ml during treatment). Sanitary towel usage was significantly reduced in patients treated with mefenamic acid and tranexamic acid. CONCLUSIONS: Tranexamic acid given during menstruation is a safe and highly effective treatment for excessive bleeding. Patients with dysfunctional uterine bleeding should be offered medical treatment with tranexamic acid before a decision is made about surgery.