Mefenamic acid: an under-rated antirheumatic?

Solvatomorphism and first-time observation of acid-acid catemer in 4-phenylamino-benzoic acids

To investigate the polymorphism in 4-phenylamino-benzoic acids (4-PABAs) in general, and the effect on the polymorphism of these compounds exerted by substitution in particular, a series of 4-PABAs (1-8) varying in the substitution position and pattern were synthesized, and their polymorphic behavior was investigated for the first time. A relatively comprehensive polymorph screening led to the discovery of two forms, one solvent-free and the other solvate, for compounds 1, 3 and 8, and one form for the other compounds. The crystal structures were determined by single-crystal XRD. All the 4-PABAs in the crystal structures are highly twisted, and all the solvent-free crystals are based on the conventional acid-acid dimer motif, except for 2, which has a rarely observed acid-acid catemer motif. Two of the solvates (1-S and 8-S) have pyridine in the lattice while the other (3-S) has dichloromethane. The observation indicates that neither conformational flexibility or substitution alone nor the combination of both leads to polymorphism in these compounds, which is in dramatic contrast to the polymorphism of fenamic acids. The thermal properties of each system were investigated by differential scanning calorimetry and desolvation of the solvates was studied by thermogravimetric analysis. Hirshfeld surface analysis and molecular dynamics simulation were performed to study the mechanism of polymorphism and the intermolecular interactions contributing to the formation and stability of each crystal form.

Double substitution leads to a highly polymorphic system in 5-methyl-2-m-tolylamino-benzoic acid

Substitution on both aromatic rings of fenamic acid led to a highly polymorphic system in 5-methyl-2-m-tolylamino-benzoic acid, in contrast to the two mono-substituted analogs, which had only one or two forms obtained.

Assessing the relative sensitivity to change of rheumatoid arthritis activity measures: is the type of treatment an important third variable?

Observational studies and meta-analyses of controlled clinical trials have been used to identify which measures of rheumatoid arthritis activity are most sensitive to change. These analyses often pool studies of different drugs, although it is not known if arthritis activity measures are differentially responsive to different drugs. In meta-analyses, estimates of the relative sensitivity to change of different measures may also be confounded by differences in drug efficacy, if studies of different drugs contribute different measures to the meta-analysis. To determine if the type of treatment acts as an important effect modifier or confounder in studies of the relative sensitivity to change of arthritis activity measures, we computed effect sizes for four measures (weighted tender joint count, grip strength, duration of morning stiffness, and erythrocyte sedimentation rate) used in each of 16 trials of five different disease-modifying antirheumatic drugs (methotrexate, sulfasalazine, cyclosporin A, intramuscular gold, and D-penicillamine) in rheumatoid arthritis. In a complete factorial analysis of variance, effect sizes differed significantly among drugs (p = 0.0006), but differed only marginally among measures (p = 0.08). No interaction was detectable between drugs and measures. These results suggested that effect modification by drugs was not present, but that pooled estimates of the sensitivity to change of different measures may be confounded in meta-analyses, if trials of more efficacious drugs contribute different measures than trials of less efficacious drugs. In a similar analysis of 26 trials of nine nonsteroidal anti-inflammatory drugs, we found significant differences in effect sizes among measures (p < 0.0001), but no differences among drugs (p = 0.96), and no interaction between drugs and measures. This study suggests that pooled analyses of the relative sensitivity to change of arthritis activity measures based on trials of different disease-modifying drugs may be confounded by drug effects, but confounding by drug effects is unlikely if these meta-analyses are based on trials of different nonsteroidal anti-inflammatory drugs. Although the power of these analyses to detect small interaction effects was limited, effect modification by drugs was not observed, indicating that the measures we examined were not strongly differentially responsive to different drugs.

Use of mefenamic acid

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Clinical therapeutic trial of sodium meclofenamate and naproxen in rheumatoid arthritis, with comments on the use of placebos in clinical trials

Forty patients with active rheumatoid arthritis were entered into a single-blind study of 12-weeks' duration to compare the efficacy and tolerance of 100 mg sodium meclofenamate 3-times daily and 250 mg naproxen twice daily. Disease activity was defined by the presence of a Ritchie Articular Index score of greater than 15. Patients were assessed at 4-week intervals. Analysis of variance of the data from those patients who completed 12 weeks in the trial showed that in the sodium meclofenamate group there was a significant improvement in articular index, left grip strength, pain severity and patients' global assessment over the course of the study. In the naproxen group, there was a significant improvement in articular index, grip strength and pain severity over the study. Pairwise comparisons showed that morning stiffness improved significantly from baseline to 12 weeks only, in both treatment groups. There were no significant differences between the two treatment groups for any of the measurements at any time period during the study. In the sodium meclofenamate group, there were 4 drop-outs due to inadequate efficacy and 6 in the naproxen group. Four patients in the sodium meclofenamate group and 2 patients in the naproxen group dropped out of the study because of side-effects, primarily nausea. These results suggest that sodium meclofenamate was equally well tolerated and as effective as naproxen in the treatment of rheumatoid arthritis in this group of patients.

A double-blind, crossover trial of mefenamic acid, sulindac and flurbiprofen in rheumatoid arthritis

A double-blind crossover trial was carried out in 24 patients to compare the effects of mefenamic acid, flurbiprofen, sulindac and placebo. Each drug was given for 2 weeks, the treatment sequence being randomized. Daily doses were 1500 mg mefenamic acid, 150 mg flurbiprofen or 150 mg sulindac. All of the active drugs were significantly superior to placebo in terms of pain score, patients' assessment, articular index of joint tenderness, and duration and severity of morning stiffness. There was improvement in grip strength compared with placebo, but the differences were not statistically significant with sulindac. There was slight reduction in joint circumference but this was only statistically significant in the right hand with flurbiprofen and sulindac. No significant differences were found in technetium uptake in knee joints. The three drugs appeared to be equally effective and tolerated, and no significant differences were noted.