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At least 19 recordsLinked to original sources

Some studies on peripheral actions of mephenesin, methocarbamol and diazepam.

1. Mephenesin, methocarbamol and diazepam abolished polysynaptic reflex contractions of the cat tibialis anterior muscle elicited by stimulation of the homolateral femoral nerve.2. Mephenesin and methocarbamol caused a prolongation of the mean refractory period of directly or indirectly stimulated skeletal muscle. These effects were due to a direct action on the muscle fibres. There was no effect on responses to single stimuli.3. The increase in refractory period produced by mephenesin was greater in indirectly than in directly stimulated rat diaphragms. Experiments using the isolated phrenic nerve suggest that this difference is due to the local anaesthetic action of mephenesin.4. In the indirectly stimulated cat tibialis anterior muscle high frequency stimulation resulted in a non-maintained tetanus in the presence of mephenesin and methocarbamol.5. Diazepam was without peripheral effects on the responses of skeletal muscle.6. The results with mephenesin and methocarbamol are discussed in relation to their mode of action in reducing muscle spasm.

Action Potentials↗

[Severe contact dermatitis caused by mephenesin].

INTRODUCTION: Mephenesin is a muscle relaxant, mostly applied locally in trauma. It is a component of Traumalgyl cream in association with phenylbutazone. Contact dermatitis due to mephenesin is exceptional. CASE REPORT: We report here a case of a woman who developed after application of Traumalgyl cream purpuric dermatitis, erythema multiforme-like and urticarial lesions. Patch-tests were strongly positive (+ + +) for both Traumalgyl cream and mephenesin and (+) for phenylbutazone. Improvement of the lesions was observed within 3 weeks. DISCUSSION: Physicians must be aware of the risk of severe contact dermatitis after application of products including mephenesin because of their widely prescription.

Adult↗

Mephenesin, methocarbamol, chlordiazepoxide and diazepam: actions on spinal reflexes and ventral root potentials.

1. Dose levels of mephenesin, methocarbamol, chlordiazepoxide and diazepam which abolished polysynaptic reflex contractions had no effect on monosynaptic knee-jerk reflexes in chloralose anaesthetized cats.2. Ventral root potentials were recorded following stimulation of the corresponding dorsal root (L7 or S1), and the areas of the mono- and polysynaptic components were measured by planimetry.3. Dose levels of the drugs which abolished polysynaptic reflex contractions reduced the areas of the polysynaptic component of the ventral root potentials by about 50%. Mephenesin and methocarbamol reduced the area of the monosynaptic component to a similar extent. Chlordiazepoxide was less potent in this respect while diazepam was without effect at this dose level.4. Linear regression lines were calculated for the reduction in the mono- and polysynaptic components of ventral root potentials with increasing doses of each of the four drugs. With methocarbamol and mephenesin the lines were parallel and coincident. With chlordiazepoxide and diazepam they were parallel but not coincident. Large doses of diazepam were required to reduce the area of the monosynaptic component, this drug being the only one of the four tested to have a differential action on the two components which was statistically significant.5. The results are discussed in terms of depressant actions of the drugs on alpha-motorneurones, effects of the drugs at higher centres concerned with motor function, and the lack of evidence that spinal interneurones represent a specific site of action for centrally acting skeletal muscle relaxants.

Animals↗

The flexor reflex mediated by group II afferent fibers: effects of morphine-HCl and mephenesin.

The effects of morphine-HCl and mephenesin on the flexor reflex mediated by group II afferent fibers were investigated. The flexor reflex was recorded by means of the electromyogram (EMG) evoked in the muscle tibialis anterior by stimulation of the ipsilateral tibial nerve in urethane-alpha-chloralose anesthetized rats. Afferent volleys corresponding to the phasic EMG component of the flexor reflex with 7.6-msec latency (flexor EMG: fEMG) were also recorded using the double volley technique. The threshold of the afferent volleys mediating the fEMG was approximately twice as high as that of the most excitable afferent volleys, which were considered the spikes of group I afferent fibers, and the conduction velocity of the afferent volleys was 39.9 +/- 3.2 m/sec. Morphine-HCl (5 mg/kg, i.v.) did not change the amplitude of the fEMG, but mephenesin (40 and 80 mg/kg, i.v.) depressed it dose-dependently. These results suggest that the fEMG is a flexor reflex mediated by group II afferent fibers, which is not affected by morphine-HCl but depressed by mephenesin.

Anesthesia↗

[Contact allergy to mephenesin].

A case of erythema multiforme-like allergic contact dermatitis due to midysalb, an ointment containing mephenesine is described. Patch testing showed marked sensitization to mephenesine, with positive reactions to different dilutions down to 0.1%. It is unlikely that the weak reaction to a further component, ethylene glycol monosalicylic acid ester, is responsible for the allergy. There are several other reports in the literature, so that mephenesine must be classed as one of the few allergens that cause reactions reminiscent of erythema multiforme.

Administration, Topical↗

Specificity and potency of N-methyl-D-aspartate glycine site antagonists and of mephenesin on the rat spinal cord in vitro.

The potency, specificity and reversibility of various presumed glycine site N-methyl-D-aspartate (NMDA) antagonists was studied on neonatal rat spinal cord using the grease gap technique. 5,7-Dichlorokynurenate was the most potent and specific glycine site antagonist among the compounds tested. On the other hand mephenesin was a weak non-specific excitatory amino acid (EAA) antagonist; reduction of the response to NMDA was not reversed by D-serine. The EAA antagonist properties of mephenesin could explain its mode of action at the cellular level. The lack of effect of D-serine alone suggests that in our experimental conditions glycine sites on spinal neurones are occupied by an endogenous ligand.

Animals↗

Site of action of chlorpromazine and mephenesin in experimental tetanus.

The anti-tetanus activities of chlorpromazine and mephenesin have been determined quantitatively in intact, spinal and decerebrate rabbits with local tetanus. The activity of chlorpromazine in the spinal animal differed from that in the intact and decerebrate animal and depended on the level of brain-stem section. Mephenesin was equally effective in all preparations and probably suppressed tetanus by blocking transmission in motor pathways in the spinal cord.

Animals↗

Mephenesin contact dermatitis with erythema multiforme features.

5 patients, all using a mephenesin -containing ointment, with an acute contact dermatitis also presented an id-like spread with erythema multiforme features. In 4 patients, patch tests were performed and since mephenesin was the common allergen in each of these cases, we may assume that this is also the cause of the erythema multiforme-like lesions.

Adolescent↗

Rigidity in rats due to radio frequency decerebration and effects of chlorpromazine and mephenesin.

Bilateral radio frequency (RF) lesions of the midbrain were produced in an attempt to establish a non-bleeding method of producing decerebrate rigidity in rats. Marked extensor rigidity occurred with a high reproducibility in hindlimbs without the appearance of voluntary movement. Stretch reflex tension induced by repetitive dorsiflexion of the hindfeet was employed as a measure of the intensity of rigidity. Chlorpromazine-HCl (0.1-1 mg/kg, i.v.) and mephenesin (10-50 mg/kg, i.v.) which depress intercollicular decerebrate rigidity, reduced the RF decerebrate rigidity. These results suggest that RF decerebrate rigidity can be used instead of intercollicular transection rigidity in the pharmacological and physiological studies.

Animals↗

Determination of mephenesin in plasma by high-performance liquid chromatography with fluorimetric detection.

A procedure for the determination of the CNS-active muscle-relaxant mephenesin in plasma samples is described. The method involved a single-step extraction with diethyl ether followed by high-performance liquid chromatography separation and fluorimetric detection. Linearity of the detection response was observed between 1 ng/ml, which is the limit of determination, and 500 ng/ml. Inter-day assays, including quality-control samples, performed over a 4-month period, showed the method to be reproducible and precise, and suitable for routine analysis in pharmacokinetic studies.

Chromatography, High Pressure Liquid↗

An evaluation of the structure-activity relationships of a series of analogues of mephenesin and strychnine on the response to pressure in mice.

1. A range of compounds structurally related to the centrally acting muscle relaxant mephenesin and to the chemical convulsant strychnine were synthesized and tested for their ability to alter the threshold pressures for the onset of high pressure convulsions in mice. 2. The ability of both groups of compounds to alter the threshold pressure for convulsions was found to be dependent on the nature of a simple molecular skeleton. Thus, compounds that possessed a negatively polarized group located both in the same plane as and some 4.5 A from an aromatic nucleus increased the thresholds whereas compounds with a positively polarized group at the same location reduced the thresholds. 3. These findings support the suggestion that pressure elicits convulsions via a selection action on a receptor protein complex rather than via some general perturbation of the lipid regions of cellular membranes.

Animals↗