A new chemically modified carbon paste electrodes based on Fe (III) schiff base (Fe (III)-SBMCP)-containing graphite pastes were prepared and evaluated as electrochemical sensor for the voltammetric determination of mefenamic acid and indomethacin in aqueous solutions. The measurements were carried out by application of the differential pulse voltammetry (DPV) method in phosphate buffer solution with pH 3.5. Fe (III) loaded in schiff base can increase anodic peak currents by adsorption of mefenamic acid and indomethacin on electrode surface. The prepared electrode shows voltammetric responses with high sensitivity for mefenamic acid and indomethacin in optimal conditions, which makes it very suitable for simultaneous determination of these compounds. The proposed method was successfully applied for determination mefenamic acid and indomethacin in commercial tablet samples.

PURPOSE: In this paper we seek to verify the differences in dissolution behavior between class I and class II drugs and to evaluate the suitability of two new physiologically based media, of Simulated Gastric Fluid (SGF) and of milk for their ability to forecast trends in the in vivo performance of class II compounds and their formulations. METHODS: Dissolution behavior of two class I drugs, i.e. acetaminophen and metoprolol, and of three class II drugs, i.e. danazol, mefenamic acid and ketoconazole, was studied with USP Apparatus 2 in water, SGF, milk, Simulated Intestinal Fluid without pancreatin (SIFsp) and in two media simulating the small intestinal contents in the fed (FeSSIF) and fasted (FaSSIF) states, respectively. RESULTS: Class I powders dissolved rapidly in all media tested. Acetaminophen dissolution in milk was slow from one tablet formulation, in all other cases dissolution was more than 85% complete in 15 minutes. The dissolution rate of metoprolol was shown to be dependent on formulation and manufacturing method, and one of the three tablet formulations did not meet compendial specifications (80%/30 minutes). Dissolution behavior of class II drugs was greatly affected by choice of medium. Dissolution from a capsule formulation of danazol proved to be dependent on the concentration of solubilizing agents, with a the 30-fold increase in percentage dissolved within 90 minutes upon changing from aqueous media without surfactants to FaSSIF. Use of FeSSIF or milk as the dissolution medium resulted in an even greater increase in percentage dissolved, 100 and 180-fold respectively. Dissolution of the weak acid mefenamic acid from a capsule formulation is dependent on both pH and bile salt concentration, which leads to an offset between increased bile salt concentration and lower pH in the fed state compared to the fasted state medium. The weak base ketoconazole showed complete dissolution from a tablet formulation in Simulated Gastric Fluid without pepsin (SGFsp) within 30 minutes, 70% dissolution in 2 hours under fed state simulated upper jejunal conditions but only 6% dissolution in 2 hours under fasted state conditions. CONCLUSIONS: As predicted, dissolution of class II drugs proved to be in general much more dependent on the medium than class I drugs. With the array of compendial and physiological media available, it should be possible to design a suitable set of tests to predict the in vivo dissolution of both class I and II drugs from immediate release formulations.

Citric acid-polyethylene glycol-citric acid (CPEGC) triblock dendrimers as biocompatible compounds containing G(1), G(2) and G(3) were applied as the drug-delivery systems. Some of the small size molecules and drugs are trapped with the above-synthesized dendrimers. The guest molecules, which are hydrophobic when trapped into the suitable sites of dendrimers, are becoming soluble in aqueous solution. The quantity of trapped molecules and drugs such as 5-amino salicylic acid (5-ASA), pyridine, mefenamic acid, and diclofenac was measured. The drug/dendrimer complexes remained in room temperature for about 10 months and after this long time they were stable and the drugs were not released. Also, the controlled release of the above-mentioned molecules and drugs in vitro conditions was investigated. The structure definition and controlled release of the molecules and drugs were carried out using different spectroscopy methods.

The dissolution profile and solubility of two polymorphic forms of mefenamic acid were studied in solvent mixtures of ethanol-water and ethyl acetate-ethanol. The solubility parameter (delta) was used to study the effect of polarity on the solubility behavior of the two polymorphs. Differential scanning calorimetry and infrared spectroscopy were performed on the original powders and on the solid phases after contact with the solvent systems for the characterization and identification of the polymorphs. The dissolution rates of both polymorphs is greater in the less polar mixtures (ethyl acetate-ethanol) of lower solubility parameter values. Form II showed larger dissolution rates and saturation concentrations than Form I in all the solvent systems studied. The solid phase of Form II converts totally to Form I after equilibration with the solvents. The rate of conversion was faster in the least polar mixtures. The solubility of both polymorphs reaches a single maximum at 80% ethyl acetate in ethanol, delta = 20.09 MPa1/2. The modified extended Hildebrand method was used to predict the solubility profile of each polymorph. A single equation was obtained for both polymorphs which includes the solubility parameter of the mixtures and the logarithm of the solubility mole fraction of each polymorph in water. The Hildebrand solubility parameter of mefenamic acid is independent of the crystalline form and was determined from two methods giving quite similar values, delta 2 = 20-21 MPa1/2.

Mefenamic acid (MFA) has anti-convulsant and pro-convulsant effects in vivo, and has been shown to potentiate and inhibit GABAA (gamma-aminobutyric acid) receptors in vitro. In this study, whole-cell currents were recorded from Xenopus oocytes and human embryonic kidney (HEK) cells expressing human recombinant GABAA receptors to resolve the molecular mechanisms by which MFA modulates GABAA receptor function. We demonstrate that MFA potentiated GABA-activated currents for alpha1beta2 gamma2S (EC50 = 3.2 +/- 0.5 microM), but not for alpha1beta1 gamma2S receptors. MFA also enhanced GABA-activated responses and directly activated alpha1beta2/beta3 GABAA receptors, but inhibited responses to GABA on alpha1beta1 constructs (IC50 = 40 +/- 7.2 microM). A comparison of beta1, beta2 and beta3 subunits suggested that the positive modulatory action of MFA involved asparagine (N) 290 in the second transmembrane domain (TM2) of the beta2 and beta3 subunits. Mutation of N290 to serine (S) markedly reduced modulation by MFA in alpha1beta2(N290S)gamma2S receptors, whereas alpha1beta1(S290N)gamma2S constructs revealed potentiated responses to GABA (EC50 = 7.8 +/- 1.7 microM) and direct activation by MFA. The potentiation by MFA displayed voltage sensitivity. The direct activation, potentiation and inhibitory aspects of MFA action were predominantly conferred by the beta subunits as the spontaneously active homomeric beta1 and beta3 receptors were susceptible to modulation by MFA. Molecular comparisons of MFA, loreclezole and etomidate, agents which exhibit similar selectivity for GABAA receptors, revealed their ability to adopt similar structural conformations. This study indicates that N290 in TM2 of beta2 and beta3 subunits is important for the regulation of GABAA receptor function by MFA. Our data provide a potential molecular mechanism for the complex central effects of MFA in vivo.

Ibuprofen and mefenamic acid are weak, competitive inhibitors of cyclooxygenase-2 (COX-2) oxygenation of arachidonic acid (AA) but potent, noncompetitive inhibitors of 2-arachidonoylglycerol (2-AG) oxygenation. The slow, tight-binding inhibitor, indomethacin, is a potent inhibitor of 2-AG and AA oxygenation whereas the rapidly reversible inhibitor, 2'-des-methylindomethacin, is a potent inhibitor of 2-AG oxygenation but a poor inhibitor of AA oxygenation. These observations are consistent with a model in which inhibitors bind in one subunit of COX-2 and inhibit 2-AG binding in the other subunit of the homodimeric protein. In contrast, ibuprofen and mefenamate must bind in both subunits to inhibit AA binding.

The formation and the properties of luminescent complexes of europium and terbium with a variety of organic ligands have been investigated in aqueous solutions. The ligands used include model compounds such as thenoyltrifluoroacetone and pyridine-2,6-dicarboxylic acid and organic analytes of biological or pharmaceutical interest. It is shown that the formation and the luminescent properties of these complexes depend at first on several parameters including the pH and the buffer, the synergic agent and the surfactant. In neutral solutions, trioctylphosphine oxide in the presence of Triton X-100 may act as a co-ligand to promote complex formation and protect the complex from radiationless deactivation processes. Working in slightly alkaline solutions in the presence of EDTA and hexadecyltrimethylammonium chloride may induce the deprotonation of a second coordinating group and favour the formation of a new complex with stronger luminescent properties. In both cases, the luminescence lifetimes are then ultimately related to the energy gap between the ligand triplet and the resonance level of the ion and to the number of water molecules coordinated to the lanthanide ion.

The prostaglandin endoperoxide H synthase-1 (PGHS-1) and prostaglandin endoperoxide H synthase-2 (PGHS-2) are the targets of non-steroidal anti-inflammatory drugs (NSAIDs). The high degree of selectivity for inhibition of PGHS-2 shown by certain compounds appears to stem from two mechanisms (time-dependent, time-independent inhibition) by which they interact with each isoform. Molecular models of the complexes between indomethacin, fenamates, 2-phenylpropionic acids and the selective cyclooxygenase-2 (COX-2) inhibitors, with the cyclooxygenase active site of human PGHS-2 have been built by combining homology modelling, conformational searching and automated docking techniques. The stability of the resulting complexes has been assessed by molecular dynamics simulations combined with extended linear response calculations. The results allow us to identify regions of biological significance consistent with both X-ray crystallographic and kinetic results. The selective PGHS-2 inhibitors exploit the extra space of a side-pocket in the active site of PGHS-2 that is not found in PGHS-1. The results obtained point out a marked relationship between the experimental affinity and the electrostatic interaction energy alone for a series of NSAIDs. Analysis of the structural and the energetic data provides evidence supporting that network of hydrogen bonds between Tyr355, Glu524, Arg120 and Arg513 might be involved in mediating the binding of the time-dependent inhibitors of PGHS-2.

Pharmaceuticals and personal care products are an emerging class of environmental pollutants. Photolysis is expected to be a major loss process for many of these compounds in surface waters, including the common non-steroidal anti-inflammatory drug mefenamic acid. The direct photolysis solar quantum yield of mefenamic acid was observed to be 1.5+/-0.3x10(-4). Significant photosensitization was observed in solutions of Suwanee River fulvic acid and Mississippi River water, as well as for the model photosensitization compounds 3'-methoxyacetophenone, 2-acetonaphthone and perinaphthenone. Quenching, sparging and light-filtering experiments suggested a direct reaction of mefenamic acid with excited triplet-state dissolved organic matter as the major photosensitization process. The persistence of the model photosensitizer suggests that the photosensitization by perinaphthenone occurs either by triplet-energy transfer or an electron transfer followed by rapid regeneration of the sensitizer. Due to its low quantum yield, the loss of mefenamic acid in sunlit natural waters is expected to depend on both direct and indirect photodegradation processes.

Mefenamic acid is a problematic drug in granulation, tableting, and dissolution due to its poor solubility, hydrophobicity, and tendency to stick to surfaces. In most cases, the specifications of a drug by the pharmacopoeia include identification and purity, but they do not describe the physicochemical drug properties precisely. To characterize the mefenamic acid particle size, surface area measurements, X-ray pattern, differential scanning calorimetry (DSC), wettability, crystal habit, and compression behavior of different batches from two manufacturers were investigated. Due to larger particle size and better wettability, mefenamic acid of Il Yang type was easier to handle in a granulation process. The compression behavior of both types was nearly the same, although particle size, crystal habit, and wettability were very different.