Modeling population pharmacokinetics of morniflumate in healthy Korean men: extending pharmacometrics analysis to niflumic acid, its major active metabolite.

This study aimed to quantify and explain inter-subject variability in morniflumate pharmacokinetics and identify effective covariates through population pharmacokinetics modeling. Models were constructed using bioequivalence pharmacokinetics results from healthy Korean males and individual physiological and biochemical parameters. Additionally, we incorporated previously reported pharmacokinetics results of niflumic acid, a major active metabolite of morniflumate, to extend the established population pharmacokinetics model and predict niflumic acid pharmacokinetics. Moreover, we used quantitative reports of leukotriene B4 (LTB4) synthesis inhibition in response to niflumic acid exposure to predict drug efficacy using Sigmoid Emax model. Population pharmacokinetics profiles of morniflumate were described using a multi-absorption (5-sequential) two-compartment model, and analysis of inter-individual variability suggested that volume of distribution in peripheral compartment was correlated with body mass index (BMI). Model simulation results showed that individuals with lower BMI had higher plasma concentrations of morniflumate and niflumic acid, resulting in increased and sustained inhibition of LTB4 synthesis. Under steady-state conditions, average plasma concentrations of morniflumate and niflumic acid were 2.66-2.68 times higher in group with a BMI of 17.36 kg/m2 compared to the group with a BMI of 28.41 kg/m2. Additionally, inhibition of LTB4 synthesis was 1.02 times higher in group with a BMI of 17.36 kg/m2 compared to group with a BMI of 28.41 kg/m2, and the fluctuation was significantly reduced from 6.06 to 0.01%. These findings suggest that the concentration of active metabolite in plasma following morniflumate exposure was lower in the obese group compared to the normal group, thus potentially reducing the drug's efficacy.

Comparative pharmacokinetic and bioequivalence evaluation of two formulations of morniflumate 350-mg tablets in healthy male subjects
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BACKGROUND: Morniflumate is a nonsteroid anti-inflammatory drug (NSAID) that inhibits cyclooxygenase-1, 2 (COX-1, 2). OBJECTIVE: This study aimed to compare the pharmacokinetics (PKs) and assess the bioequivalence of two different formulations of morniflumate 350-mg tablets in healthy Korean male subjects. METHODS: A randomized, single-dose, two-period, two-sequence crossover study was conducted with 38 subjects. Subjects received a single dose of two tablets of either a test or a reference formulation and the alternated formulation in the next period. Serial blood samples for the PK analysis were collected over 12 hours. PK parameters were determined by a noncompartment analysis. PK parameters, including the maximum concentration (Cmax) and the area under-the-concentration-time curve from time zero to the time of the last quantifiable concentration (AUClast) were compared in bioequivalence tests. RESULTS: The Cmax of the test and reference formulations were 985.72 ± 6.80 mg/L and 947.09 ± 6.73 mg/L, respectively, while the AUClast values were 2675.92 ± 7.84 mg×h/L and 2653.06 ± 7.78 mg×h/L, respectively. The geometric mean ratios (90% confidence interval) of the test formulation to the reference formulation for Cmax and AUClast were 1.0715 (0.9469 - 1.2124) and 1.0592 (0.9592 - 1.1695), respectively. CONCLUSIONS: The new formulation of morniflumate 350-mg tablet showed a PK profile similar to that of the marketed formulation, and the results of this study fell within in the conventional criteria of bioequivalence.
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Efficacy and safety of morniflumate for the treatment of symptoms associated with soft tissue inflammation.

The effectiveness of nonsteroidal antiinflammatory drugs (NSAIDs) for the management of pain in osteoarthritis and other musculoskeletal diseases is well documented. The role of NSAIDs is less clear in the treatment of conditions involving soft tissue inflammation, including the airways, ear-nose-throat (ENT) system and urogenital tract. These conditions are often treated inappropriately with antibiotics. Morniflumate, the ß-morpholinoethyl ester of niflumic acid, is a member of the fenamate family of NSAIDs indicated for the treatment of inflammatory conditions (with or without pain) affecting airways, the ENT system, urogenital tract and the osteoarticular system. Morniflumate has a 30-year history of clinical use, particularly for the treatment of pain associated with paediatric ENT infection. This article reviews evidence supporting the efficacy and safety of morniflumate. Based on available evidence and the favourable tolerability profile emerging from extensive clinical use, morniflumate appears to be a valid and well-tolerated alternative to other NSAIDs, or to antibiotics, for the treatment of pain and other symptoms of soft tissue inflammation.

Targeting kidney CLC-K channels: pharmacological profile in a human cell line versus Xenopus oocytes.

CLC-K chloride channels play a crucial role in kidney physiology and genetic mutations, affecting their function are responsible for severe renal salt loss in humans. Thus, compounds that selectively bind to CLC-Ka and/or CLC-Kb channels and modulate their activity may have a significant therapeutic potential. Here, we compare the biophysical and pharmacological behaviors of human CLC-K channels expressed either in HEK293 cells or in Xenopus oocytes and we show that CLC-K channel properties are greatly influenced by the biochemical environment surrounding the channels. Indeed, in HEK293 cells the potentiating effect of niflumic acid (NFA) on CLC-Ka/barttin and CLC-Kb/barttin channels seems to be absent while the blocking efficacy of niflumic acid and benzofuran derivatives observed in oocytes is preserved. The NFA block does not seem to involve the accessory subunit barttin on CLC-K1 channels. In addition, the sensitivity of CLC-Ks to external Ca(2+) is reduced in HEK293 cells. Based on our findings, we propose that mammalian cell lines are a suitable expression system for the pharmacological profiling of CLC-Ks.

Determination of talniflumate and niflumic acid in human plasma by liquid chromatography-tandem mass spectrometry.

A simple and rapid quantification method was developed for determining both talniflumate and niflumic acid in human plasma. After simple protein precipitation with acetonitrile, the analytes were chromatographed on a reversed-phase C(18) column and detected by LC/MS/MS with electrospray ionization. The assay accuracy and precision were within the FDA guidance for the analytical method validation. This method was used to measure the plasma concentrations of both compounds from healthy subjects after a single oral dose of talniflumate, 740 mg.

Effect of food on systemic exposure to niflumic acid following postprandial administration of talniflumate.

PURPOSE: Talniflumate was designed as a prodrug of niflumic acid, a potent analgesic and anti-inflammatory drug, which is widely prescribed for treating rheumatoid diseases. The prandial effect on talniflumate absorption remains unclear; therefore, this study investigated the effect of food on the systemic exposure to niflumic acid in healthy volunteers. METHODS: Volunteers received a single 740-mg dose of talniflumate 30 min after consuming a high-fat breakfast, a low-fat breakfast, or no food (fasting condition). Plasma concentrations of both talniflumate and niflumic acid were measured using validated high-performance liquid chromatography coupled to tandem mass spectrometry. RESULTS: The maximum concentration of niflumic acid was 224 +/- 193 ng/ml at approximately 2.7 h in the fasted condition compared with 886 +/- 417 ng/ml (p < 0.05) at 1.8 h and 1,159 +/- 508 ng/ml (p < 0.01) at 2.2 h with the low- and high-fat meals, respectively. The mean area under the curve from zero to infinity (AUC(inf)) values after the low- and high-fat meals were four- and fivefold, respectively, the value while fasting (p < 0.05). CONCLUSIONS: It is strongly recommended that talniflumate be taken after a meal to increase systemic exposure to its active metabolite. Our results suggest a reduction in the daily dosage of talniflumate when taken with food.

[Investigation of solubility properties of nifluminic acid containing cyclodextrins and polyvidone]. / Nifluminsav oldékonysági tulajdonságainak növelése ciklodextrin és polividon felhasználásával.

One of the most important task of the pharmaceutical technology is to reach a possible high gastrointestinal absorbtion of the active ingredient. Therefore, it is necessary to have a good solubility in the gastric/intestinal medium. In this way the applied drug quantity and unwanted side effects can be reduced with solubility increasing. The water-insoluble drug's solubility and bioavailability can be increased by the alteration of their physicochemical properties. Nifluminic acid is a frequently used anti-inflammatory drug with low aqueous solubility. Inclusion complexation with cyclodextrins is an efficacious method to improve the solubility, stability and bioavailability. Ternary systems were prepared and investigated to use nifluminic acid, hydoxypropyl-beta-cyclodextrin and polyvidone. The aims of the study were to investigate the solubility rate, the in vitro diffusion ability, to determine the n-octanol/water partition coefficient, and to study the thermoanalitycal properties of products. The results suggested that complexation with cyclodextrin and the use of polyvidone is better method than to prepare binary systems. Inclusion complexation was presumed in the event of the ternary composition to improve the bioavailability of nifluminic acid.

Simultaneous determination of niflumic acid and its prodrug, talniflumate in human plasma by high performance liquid chromatography.

A high-performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of niflumic acid and its prodrug, talniflumate, in human plasma. Niflumic acid and talniflumate were eluted isocratically with methanol-water (73:27, v/v, adjusted to pH 3.5 by acetic acid) at a fl ow rate of 1 mL/min. Indomethacin was used as an internal standard. Signals were monitored by an UV detector at 288 nm. Retention times of indomethacin, niflumic acid and talniflumate were 5.9, 7.2 and 13.5 min, respectively. Calibration plots were linear over the range 50-5000 ng/mL for niflumic acid and 100-5000 ng/mL for talniflumate. The limits of quantitation were 50 ng/mL for niflumic acid and 100 ng/mL for talniflumate. The intra- and inter-day relative standard deviations (RSD) of niflumic acid and talniflumate were less than 10% and the accuracies were higher than 90%. This method is rapid, sensitive and reproducible for the determination of niflumic acid and talniflumate in human plasma.

Detection of the non-steroidal anti-inflammatory drug niflumic acid in humans: a combined 19F-MRS in vivo and in vitro study.

This study describes for the first time results of a (19)F-MRS study on humans exposed to the fluorinated non-steroidal anti-inflammatory drug niflumic acid. The accumulation and elimination of this commercially available selective prostaglandin synthase inhibitor is studied after an oral bolus in the human liver, in blood plasma and in urine samples. The in vivo spectra of the liver display two resonances with a similar increase in signal intensity during the investigation period of 240 min. One resonance refers to the parent compound niflumic acid (P), whereas the second resonance corresponds to a metabolite (M1) formed by the biotransformation by liver enzymes. The spectroscopic comparison with model compounds suggests 4'-hydroxyniflumic acid as the metabolite. During the entire experiment the concentration ratios of these resonances (P/M1) ranged between 0.7 and 0.9, indicating a high metabolite concentration most probably due to an efficient first pass metabolism. Both resonances (P, M1) were observed in the in vitro study of the blood plasma samples after plasma protein denaturation. However, in comparison to the liver spectra, the amount of the metabolite M1 is very small with a P/M1-ratio of 36.6 after 90 min and 16.1 after the end of measurement. This finding suggests an efficient biliary excretion of the metabolite M1, which bypasses the blood circulation system. Both resonances are also identified in the native urine samples. The signal intensity of the parent compound dominates the spectra of all urine samples, whereas the signal intensity of M1 increases slowly reaching a similar value to the parent compound P at the end of the measurement. This observation demonstrates an effective renal elimination of niflumic acid and suggests the existence of an enterohepatic circuit with a re-entry mechanism for the biliary excreted metabolite M1. In the urine spectra, an additional metabolite M2 is found. This resonance exhibits a low but constant signal intensity. The chemical origin of this metabolite is unclear.

Pharmacokinetic parameters and killing rates in serum of volunteers receiving amoxicillin, cefadroxil or cefixime alone or associated with niflumic acid or paracetamol.

Pharmacokinetic parameters and killing rates in serum of volunteers receiving amoxicillin, cefadroxil or cefixime alone or associated with niflumic acid or paracetamol were studied. Niflumic acid (250 mg) or analgesic and antipyretic drugs such as paracetamol (500 mg) are often combined with antibiotics to avoid inflammation and pain in acute ear, nose and throat diseases. Pharmacokinetic interactions between these two classes of drugs have been described in experimental models, and exceptionally in humans. The aim of the present investigation was to study the interactions of these two drugs with three antibiotics (amoxicillin 500 mg x 2, cefadroxil 500 mg x 2, cefixime 200 mg and one placebo capsule) on pharmacodynamic parameters and on rate of killing in the serum of six healthy volunteers receiving the antibiotic associated or not with the product in a randomized cross-over double-blind trial. The bacteria most often involved in sinusitis, bronchitis and otitis media (Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus aureus) three target diseases for oral cephalosporins and amoxicillin, were chosen for bacteriological study. Blood samples were obtained at 0.25, 0.50, 1, 1.5, 2, 4, 6 and 12 h after oral administration of antibiotics alone or associated with the drugs. There was a wash-out period of at least 1 week between the eleven sequences. Antibiotics were measured by two methods: bioassay and high performance liquid chromatography (HPLC). All serum samples obtained at peak level, 4 and 6 h were tested for killing rate. Area under the time kill curve was calculated by the trapezoidal rule method and relative bioactivity in percent was defined as follows: (AUC control - AUC test)/AUC control x 100. No pharmacokinetic interaction was found in the AUC and T1/2 of the plasma concentrations of the antibiotics or associated with the drugs, regardless of dose, as determined by HPLC or microbiological assay. For these beta-lactam antibiotics killing rate was found to be time-dependent. Bactericidal activity was improved on H. influenzae when cefixime was associated with niflumic acid and became concentration-dependent. A significant concentration relation was also found with niflumic acid or paracetamol associated with cefixime on Strep. pneumoniae.

Intracellular binding of the anti-inflammatory drug niflumic acid in the liver.

Intracellular binding of niflumic acid in the perfused rat liver was analyzed according to the model of Scatchard. The data for the binding isotherm were obtained from previously published indicator dilution experiments. The intracellular bound niflumic acid was calculated as the difference between total concentration and the concentration of the free form. The intracellular concentration of the free form was inferred from the concentration of the free form in the extracellular space under the assumption of equilibrative distribution. A Scatchard model with two classes of binding sites fits very well to the experimental curve. The high affinity class has a dissociation constant of 26.10 +/- 0.69 microM and a maximal binding capacity of 2.21 +/- 0.03 micromol (ml intracellular space)(-1); the low affinity class has a dissociation constant of 721.90 +/- 229.0 microM and a maximal binding capacity of 5.96 +/- 0.67 micromol (ml intracellular space)(-1). Probably, under in vivo conditions, the binding capacity in the cellular space exceeds that of the extracellular space. This phenomenon explains, partly at least, the high intracellular concentrations of niflumic acid found under in vivo conditions.

Inhibition of hepatic gluconeogenesis by niflumic acid correlates with the concentration of the free form.

Inhibition of hepatic gluconeogenesis by niflumic acid, a non-steroidal antiinflammatory drug, was measured in order to correlate the effect of the drug with the concentration of the free drug. The concentration of free drug was changed in two ways: (a) by changing the albumin concentration at a fixed total (free+bound) niflumic acid concentration; and, (b) by changing the drug concentration at a fixed albumin concentration. The degree of inhibition of gluconeogenesis by niflumic acid depends strictly on the concentration of the free drug, with half-maximal inhibition at 19.25 microM. This result is consistent with binding equilibrium in the extracellular space and with a flow-limited distribution between the extra- and intracellular spaces as proposed by our previous work.

Follicles play an important role in percutaneous absorption.

The relative importance of stratum corneum and follicles in percutaneous absorption is not fully understood. In order to quantitatively investigate the importance of the transappendageal route, we have previously developed a model of skin without follicles regrown dorsally on the hairless rat. Percutaneous absorption was compared, using a diffusion cell, in appendage-free skin relative to normal skin, and a predominant role of follicles for in vitro diffusion of [3H]hydrocortisone was noted. Results presented here of in vitro diffusion of tritiated hydrocortisone, niflumic acid, caffeine, and p-aminobenzoic acid, applied in acetone, confirm that appendageal diffusion is the major pathway in hairless rat skin. In the absence of follicles, the steady-state flux and the amounts diffusing in 24 or 48 h are 2-4 times lower than in normal skin. These results were confirmed in a second model in which diffusion of [3H]hydrocortisone was studied on skin samples taken one day after birth, at which time rat skin is still devoid of follicles, relative to five-day postnatal skin samples, in which follicles are fully developed. The steady-state flux and the total diffusion in 24 h were fivefold lower in follicle-free skin. These results support the view that follicles may have a far greater importance in percutaneous absorption than is generally assumed.