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PubMed1987

The effect of charcoal on mefenamic acid elimination.

Mefenamic acid suppository 500 mg was administered by rectum to eight healthy adult volunteers followed by either activated charcoal 5 g orally at hourly intervals for 7 h or an equal volume of water on two separate occasions 7 days apart. Administration of charcoal did not significantly affect the pharmacokinetic variables of mefenamic acid. Thus the beneficial effects of charcoal in the treatment of mefenamic acid overdose are largely due to interference with absorption, rather than enhancement of elimination of the drug.

Adult↗
PubMed1994

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.

Animals↗
PubMed1996

Interaction of valproic acid with nonsteroidal antiinflammatory drugs mefenamic acid and fenoprofen in normal and uremic sera: lack of interaction in uremic sera due to the presence of endogenous factors.

Valproic acid is an anticonvulsant that is strongly bound to serum albumin. The nonsteroidal antiinflammatory drugs mefenamic acid and fenoprofen are also strongly bound to albumin. We observed significant displacement of valproic acid from protein binding by mefenamic acid and fenoprofen at both therapeutic and slightly above therapeutic concentrations. The concentration of free valproic acid was higher in the uremic serum, as expected, but we observed no further displacement of valproic acid in the presence of mefenamic acid and fenoprofen. Known uremic compounds, hippuric acid and indoxyl sulfate, did not inhibit the interactions between valproic acid and mefenamic acid or fenoprofen. Treatment of uremic serum with activated charcoal at pH 3.0 removes endogenous interfering factors and corrects the binding defect of uremic serum for valproic acid. We observed significant displacement of valproic acid from protein binding by both mefenamic acid and fenoprofen in uremic serum after charcoal treatment. We conclude that endogenous factors are present in uremic sera that block interaction of valproic acid with mefenamic acid and fenoprofen.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1997

Urinary excretion of mefenamic acid and its metabolites including their esterglucuronides in preterm infants undergoing mefenamic acid therapy.

Urinary excretion of mefenamic acid (MA) and its two oxidative metabolites, M-I (3'-hydroxymethyl derivative) and M-II (3'-carboxyl derivative), and their glucuronides was investigated in preterm infants undergoing MA therapy. MA was given orally at a dose of 2 mg/kg and the dose was repeated every 24 h a maximum of three times. Urine was collected for up to 5 d after the last dose, and MA and the metabolites were determined by a newly developed HPLC. The cumulative amounts of MA and the metabolites excreted in the urine varied from 7 to 46% of the total dose administered, and were less than those reported in adults and children. Significant correlation was observed between the plasma half-life of MA and the cumulative amount of MA and the metabolites excreted in the urine. These results suggest that long plasma half-lives of MA observed in preterm infants are due mainly to low activity of drug metabolizing enzyme(s). In an infant who received the two regimens of MA therapy about 2 weeks apart, the plasma half-life of MA was shortened and the urinary excretion of the MA metabolites including their glucuronides was greatly increased during this period. It is suggested that the activities of both cytochrome P-450(s) and glucuronyltransferase(s) related to MA metabolism rapidly increased during the first month of the infant's life.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1983

A double-blind comparison of a propionic acid derivative (ibuprofen) and a fenamate (mefenamic acid) in the treatment of dysmenorrhea.

A double-blind three-way crossover design in the treatment of dysmenorrhea comparing a propionic acid derivative (ibuprofen) and a fenamate (mefenamic acid) with a placebo showed that both ibuprofen and mefenamic acid are generally superior to placebo. Statistically significant results were obtained in favor of the study drugs over placebo for the pain relief afforded by the treatments (as graded by patients) and the visual analog pain relief score, which not only ranks but also indicates the degree of pain relief as a percentage of total relief (100%). Pairwise comparisons for the ranks found mefenamic acid significantly superior to placebo (P less than .001) and ibuprofen marginally superior to placebo (P less than .06), while the visual analog pain relief scale demonstrated mefenamic acid and ibuprofen superior to placebo (P less than .001 and P less than .01, respectively). For both the patient ranking of pain relief by treatment and the visual analog pain relief scale, the results showed no significant differences between ibuprofen and mefenamic acid. Side effects occurred in 11 ibuprofen cycles, five mefenamic acid cycles, and ten placebo cycles of the 48 cycles with each agent. These were generally of minor severity or importance and were not statistically different. The need for additional analgesics and the ability to pursue normal daily activity were not different for any treatment group. The findings of this study indicate no clinical difference between a propionic acid derivative such as ibuprofen and a fenamate such as mefenamic acid in the treatment of dysmenorrhea.

Adult↗
PubMed1991

Simultaneous analysis of flunixin, naproxen, ethacrynic acid, indomethacin, phenylbutazone, mefenamic acid and thiosalicylic acid in plasma and urine by high-performance liquid chromatography and gas chromatography-mass spectrometry.

Simple and reproducible high-performance liquid chromatographic (HPLC) and gas chromatographic-mass spectrometric (GC-MS) methods have been developed for the simultaneous analysis of several acidic drugs in horse plasma and urine. Although the capillary GC-MS column provided better separation of the drugs than the reversed-phase C8 (3 microns, 75 mm) HPLC column, the total analysis time with HPLC was shorter than the total analysis time with GC-MS. The HPLC system equipped with a diode-array detector provided simultaneous screening (limit of detection 100-500 ng/ml) and confirmation (limit 1.0 micrograms/ml) of the drugs. The HPLC system equipped with fixed-wavelength ultraviolet and fluorescence detectors provided a relatively sensitive screening [limit of detection 50-150 ng/ml for ultraviolet and 10 ng/ml for fluorescence (naproxen only) detectors] of the drugs. However, the positive samples had to be confirmed by using either the diode-array detector or the GC-MS system. The GC-MS system provided simultaneous screening and confirmation of the drugs at very low concentrations (20-50 ng/ml).

Analgesics↗
PubMed1994

Non-steroidal anti-inflammatory drugs and tumor progression: inhibition of fibroblast hyaluronic acid production by indomethacin and mefenamic acid.

The antitumor effects of non-steroidal anti-inflammatory drugs (NSAIDs) have been documented in a variety of both clinical and experimental settings, although the mechanisms responsible remain unclear. In the present study, we show that the NSAIDs indomethacin and mefenamic acid inhibit the calf serum-stimulated production of hyaluronic acid (HA) in murine Swiss 3T3 fibroblasts, at concentrations where DNA synthesis is unaffected. HA is an extracellular matrix glycosaminoglycan associated with cell migration and tumor invasion. Our data suggest that one mechanism whereby NSAIDs inhibit tumor progression may be to inhibit the synthesis of HA by host fibroblasts, and that the eicosenoid pathway may represent an important control point in the growth-factor-mediated production of HA in fibroblasts. Thus the use of an agent which inhibits HA synthesis may be a novel approach to alter the invasive and metastatic properties of tumor cells in a non-cytotoxic fashion.

3T3 Cells↗
PubMed1992

Rapid and sensitive liquid chromatographic assay of mefenamic acid in plasma.

Mefenamic acid (MA) is a nonsteroidal antiinflammatory analgesic agent widely used clinically. A simple and sensitive liquid-chromatographic assay has been developed for the quantitative determination of MA in human plasma. A reverse phase, 10-microns cyano column (25 x 0.4 cm), a mobile phase of water-acetonitrile-methanol-17 M acetic acid (69:15:15:1 by volume), and an ultraviolet detection (290 nm) are used for the separation of MA and internal standard (methyl-clonazepam). MA and internal standard are extracted from acidified plasma into diethyl ether and after evaporation of the organic phase, the residue is redissolved in methanol. Calibration curves are linear in the range 0.05-3.20 micrograms/ml, and at the plasma level corresponding to the quantification limit (0.05 microgram/ml) coefficients of variation are 7.5% and 10.2% for repeatability and reproducibility studies, respectively. This assay was successfully used in the study of pharmacokinetics of MA in human plasma after a single oral administration of a low MA dose.

Carbamazepine↗
PubMed1990

Caffeine potentiates the nephrotoxicity of mefenamic acid on the rat renal papilla.

The effect of caffeine given in combination with mefenamic acid on the renal papilla was studied. Sprague-Dawley rats were divided into four groups and gavage fed either control suspension, mefenamic acid, mefenamic acid and caffeine or caffeine alone for 4 months. Semiquantitative urinalysis was performed at 3 months and showed increased haematuria in the mefenamic acid and caffeine group. There were no significant differences in serum creatinine at sacrifice. Renal histology revealed more advanced papillary necrosis in rats gavage fed mefenamic acid and caffeine compared with all other groups (p less than 0.0001). Rats fed mefenamic acid alone showed more damage than control and caffeine-fed groups (p less than 0.0001, p less than 0.0002, respectively). This suggests that caffeine potentiates the nephrotoxicity of the non-steroidal anti-inflammatory drug, mefenamic acid, on the rat renal papilla. The mechanism of this potentiation by caffeine is yet to be defined.

Animals↗
PubMed1995

Flow-injection spectrofluorimetric determination of flufenamic and mefenamic acid in pharmaceuticals.

Two sensitive and rapid flow-injection (FI) spectrofluorimetric methods are proposed for the determination of flufenamic acid (FF) and mefenamic acid (MF), based on the formation of complexes of these compounds with A1(III) in an ethanolic medium. The calibration graphs resulting from the measurements of the fluorescence at lambda exc = 351 nm and lambda em = 440 nm, and lambdaexc = 355 nm and lambda em = 454 nm for the complexes with FF and MF, respectively, are linear over the range 0.030-1.20 micrograms ml-1 for FF and 0.30-16.1 micrograms ml-1 for MF. The methods have been applied to the determination of these drugs in pharmaceutical preparations.

Administration, Topical↗
PubMed2005

Glyceride derivatives as potential prodrugs: synthesis, biological activity and kinetic studies of glyceride derivatives of mefenamic acid.

In order to reduce the gastrointestinal side effect, of mefenamic acid, its carboxylic group was condensed with the hydroxyl group of 1,2,3-trihydroxy propane 1,3-dipalmitate/stearate to give 3a and 3b. These compounds were evaluated for their gastric toxicity, anti-inflammatory activity by the carageenan induced paw oedema test and analgesic activity by the acetic acid induced writhing method. The release of mefenamic acid from the esters 3a and 3b was studied at pH 3, 4, 5 and 7.4 with direct analysis by reverse phase HPLC using acetonitrile:acetate buffer (0.1 M, pH 3.5): methanol (40:25:35) at 1 mL/min. The prodrugs showed less hydrolysis at pH 5 compared to pH 7.4 indicating that the prodrugs do not dissociate at stomach pH but release mefenamic acid at pH 7.4 in adequate amounts. The hydrolysis studies were also performed in rat plasma. A higher plasma concentration of mefenamic acid was observed in animals treated with 3a and 3b compared to the animals treated with the parent drug, and even after 8 h the concentration of mefenamic acid was 2 times higher. The peak plasma concentration of mefenamic acid in animals treated with mefenamic acid was attained in 1.5 h compared with 2 h in the case of prodrugs treated animals. The prodrugs showed less gastric ulceration compared to mefenamic acid at 100 mg/kg, a severity index of 1.10, 1.22 being observed with 3a, 3b and with mefenamic acid a severity index of 2.37 was observed. The prodrugs showed better anti-inflammatory activity compared to the parent drug and analgesic activity comparable to the parent drug. These findings suggest that the prodrugs 3a and 3b synthesized might be used as biolabile prodrugs of mefenamic acid with increased bioavailability and less gastrointestinal side effects.

Animals↗
PubMed1992

Fixed drug eruption to mefenamic acid: a report of three cases.

Mefenamic acid (Ponstan) is widely used in the treatment of dysmenorrhoea, menorrhagia, and musculoskeletal pain. Although only 17 cases of fixed drug eruption provoked by mefenamic acid have been reported in the world literature, in a 7-day period a further three patients with fixed drug eruption due to mefenamic acid presented to the dermatology out-patient clinic of the University Hospital of Wales, Cardiff. The lesions of all the patients became inflamed within a few hours of taking the drug, but two of the three patients failed to appreciate the association. There have been no further episodes of inflammation since the patients avoided mefenamic acid.

Adult↗
PubMed1991

Column-switching techniques for high-performance liquid chromatography of ibuprofen and mefenamic acid in human serum with short-wavelength ultraviolet detection.

Column-switching techniques for high-performance liquid chromatography of two acidic drugs, ibuprofen and mefenamic acid, in human serum with short-wavelength ultraviolet detection are described. The method involved extraction of the analyte from acidified serum followed by the chromatographic analysis using column switching. Three ODS columns were used each with different mobile phase, utilizing the difference of ion-pair formation or of ionization caused by pH change. The method offered high sensitivity and selectivity, with short-wavelength ultraviolet detection at 221 nm for ibuprofen and at 219 nm for mefenamic acid. The detection limits were 0.5 ng/ml (2.4 pmol/ml) for ibuprofen and 0.1 ng/ml (0.4 pmol/ml) for mefenamic acid using 1 ml of serum, both at a signal-to-noise ratio of 3. With some modifications, the principle of the method would be applicable to other acidic compounds in biological fluids.

Chromatography, High Pressure Liquid↗
PubMed2000

Treatment of menstrual migraine with prostaglandin synthesis inhibitor mefenamic acid: double-blind study with placebo.

The therapeutic effect of mefenamic acid, prostaglandin synthesis inhibitor, on pain of acute menstrual migraine and at the following days during menstrual bleeding period was studied and compared with placebo. 24 patients, 18 to 35 years old, with menstrual migraine were entered for study. They had regular menstrual cycles and they had been diagnosed as experiencing menstrual migraine without aura for more than one year. The patients were treated for 2 consecutive menstrual cycles, one cycle with 500 mg mefenamic acid and one cycle with placebo. Each drug was given at beginning of complaint and similar dose was repeated 8 hourly at following days during the menstrual bleeding period (Total dosage used 1500 mg per day). The use of medication was double blind. Pain intensity was rated by means of a 4 points scale and functional disability was rated from 0 to 3. Results showed that 79.16% of the patients showed significant pain relief with mefenamic acid as compared to 16.6% with placebo. The mean pain score of the mefenamic acid treated attacks decreased significantly from 2.46 +/- 0.5 to 0.62 +/- 1.0 at 2hr postdose. 83.3% of patients treated with mefenamic acid was able to function with or without little effort whereas 12.4% restored their activities with placebo. All the patients (100%) who showed significant initial responses to placebo experienced headache recurrence as compared to 26.3% with mefenamic acid. When considering mean pain scores, percentage of patients with pain free at 2h postdose, percentage of patients required rescue treatment, percentage of patients with headache recurrence and percentages of patients restored full activities, mefenamic acid is significantly superior to placebo in treatment of acute menstrual migraine. It might be concluded that mefenamic acid is safe and effective for treatment of acute menstrual migraine.

Adolescent↗
PubMed1989

A double-blind placebo-controlled crossover study of mebeverine and mefenamic acid in the treatment of primary dysmenorrhoea.

OBJECTIVE: i) To compare the efficacy of mebeverine, mefenamic acid and placebo in relieving the symptoms of primary dysmenorrhoea. ii) To compare the incidence of concurrent effects during treatment with mebeverine, mefenamic acid and placebo. DESIGN: Double-blind, prospectively randomised, three-way crossover study of mebeverine, mefenamic acid and placebo during three consecutive menstrual cycles. SETTING: University health centres in the UK. PATIENTS: Sixty-four females suffering from primary dysmenorrhoea who experienced pain during every menstrual cycle. INTERVENTION: Dosage was two capsules, three times daily, of mebeverine, mefenamic acid or placebo. Each mebeverine capsule contained 135 mg mebeverine hydrochloride, and each mefenamic acid capsule contained 250 mg mefenamic acid. Paracetamol (up to 2 x 500 mg) was permitted, if required, as rescue analgesia. MEASUREMENTS AND RESULTS: Details of pain severity, nausea, abdominal bloating and disruption to daily activities were recorded by means of clinician assessments and patient diaries. Patients indicated their treatment preference after three cycles. Mebeverine and mefenamic acid were superior to placebo in reducing pain severity (p less than 0.01 and p less than 0.02 respectively), and mefenamic acid reduced the level of disruption to normal activities (p less than 0.01). The number of concurrent effects reported was five during treatment with mefenamic acid and one each during treatment with placebo and mebeverine. CONCLUSIONS: Mebeverine and mefenamic acid are effective in relieving symptoms of dysmenorrhoea.

Adolescent↗
PubMed1988

Effect of magnesium hydroxide on the absorption of tolfenamic and mefenamic acids.

The effect of various antacids on the absorption of tolfenamic and mefenamic acids has been investigated in three separate crossover studies, each consisting of four phases. Single doses of magnesium hydroxide (85 mg, 425 mg and 1700 mg) or of water (150 ml) were given by mouth to 6 healthy volunteers immediately after tolfenamic acid 400 mg (Study 1), and, using an identical study design, after mefenamic acid 500 mg (Study 3). In Study 2 sodium bicarbonate 1 g, aluminium hydroxide 1 g, an antacid preparation containing both aluminium and magnesium hydroxides, or water alone were ingested with tolfenamic acid 400 mg. Plasma concentrations of tolfenamic and mefenamic acids and their cumulative excretion in urine were determined up to 24 h. Magnesium hydroxide greatly accelerated, in a dose-dependent manner the absorption of both tolfenamic and mefenamic acids. The peak times in plasma were shortened by about 1 h by 425 mg and 1700 mg magnesium hydroxide, and the peak plasma concentrations of both fenamates were elevated up to 3-fold. The area under the plasma concentration-time curve between 0 and 1 h of tolfenamic acid was increased up to 7-fold and that of mefenamic acid up to 3-fold. The total bioavailability of tolfenamic and mefenamic acids was only slightly increased. Aluminium hydroxide alone and in combination with magnesium hydroxide significantly retarded the absorption and lowered the peak plasma concentration of tolfenamic acid. Sodium bicarbonate had no significant effect on its absorption. The interaction with magnesium hydroxide leads to higher and earlier peak plasma concentrations of the fenamates.(ABSTRACT TRUNCATED AT 250 WORDS)

Antacids↗