Eperisone

Eperisone (full name: eperisone hydrochloride) is an antispasmodic drug, sold in Japan, India and Bangladesh under the brand name Myonal. Eperisone acts by relaxing both skeletal muscles and vascular smooth muscles, and demonstrates a variety of effects such as reduction of myotonia, improvement of circulation, and suppression of the pain reflex. The drug inhibits the vicious cycle of myotonia by decreasing pain, ischaemia, and hypertonia in skeletal muscles, thus alleviating stiffness and spasticity, and facilitating muscle movement. Eperisone also improves dizziness and tinnitus associated with cerebrovascular disorders or cervical spondylosis. Eperisone has a relatively low incidence of sedation when compared with other anti-spasmodic drugs; this simplifies the clinical application of the drug and makes it an attractive choice for patients who require anti-spasmodic therapy without a reduction in alertness. Eperisone also facilitates voluntary movement of the upper and lower extremities without reducing muscle power; it is therefore useful during the initial stage of rehabilitation and as a supporting drug during subsequent rehabilitative therapy.

Indications
Spastic paralysis in conditions such as cerebrovascular disease, spastic spinal paralysis, cervical spondylosis, post-operative sequelae (including cerebrospinal tumour), sequelae to trauma (eg. spinal trauma, head injury), amyotrophic lateral sclerosis, cerebral palsy, spinocerebellar degeneration, spinal vascular diseases and other encephalomyelopathies; improvement of muscular hypertonic ymptoms in conditions such as cervical syndrome, periarthritis of the shoulder, lumbago.

Presentation
Eperisone hydrochloride is available as the brand name preparation Myonal as 50 mg enteric coated tablets. An experimental form of the drug, as a transdermal patch system, has shown promising results in laboratory tests on rodents; however, this product is not currently available for human use.

Dosage and administration
In adults, the usual dose of eperisone is 50-150 mg per day, in divided doses after meals. However, the dosage is adjusted by the prescribing clinician depending on factors such as severity of symptoms, patient age and response.

Eperisone has not been established as definitely safe for paediatric use, therefore its use in paediatrics cannot be recommended without further study.

If elderly patients are treated with eperisone, it is recommended that a reduced dose is used, and the patient closely monitored for signs of psychological hypofunction during treatment.

Safety during pregnancy and breast-feeding
Eperisone has not been established to be safe for use by pregnant women; therefore the drug should only be used in pregnant women, or women who may be pregnant, if the expected therapeutic benefits will outweigh the possible risks associated with treatment. The manufacturers of Myonal recommend that the drug is not used during lactation (breast-feeding). If eperisone must be used, it is recommended that the patient stops breast-feeding for the duration of treatment. (It has been reported that Eperisone is excreted in breast milk in an animal study (in rats).

Pharmacology
IUPAC name: (2RS)-1-(4-Ethylphenyl)-2-methyl-3-piperidin-1-ylpropan-1-one monohydrochloride C17H25NO·HCl- mass number= 295.85

Skeletal muscle relaxation
Relaxation of hypertonic skeletal muscles
Improves intramuscular blood flow
Suppression of spinal reflex potentials
Reduction of muscle spindle sensitivity via motor neurons
Vasodilatation and augmentation of blood flow
Analgesic action and inhibition of the pain reflex in the spinal cord

Contraindications
Eperisone is contraindicated in patients with known hypersensitivity to the drug.

Cautions
Eperisone should be administered with care in patients with a history of hypersensitivity to any medication, or with disorders of liver function (Eperisone may aggravate hepatic dysfunction).

Weakness, light-headedness, sleepiness or other symptoms may occur. In the event of such symptoms, the dosage should be reduced or treatment discontinued. Patients should be cautioned against engaging in potentially hazardous activities requiring alertness, such as operating machinery or driving a car.

Side effects
Shock and Anaphylactoid reactions: In the event of symptoms such as redness, itching, urticaria, oedema of the face and other parts of the body, dyspnoea etc, treatment should be discontinued and appropriate measues taken.
Oculo-muco-cutaneous syndrome (Stevens Johnson Syndrome) and Toxic Epidermal Necrolysis: Serious dermatopathy such as oculo-muco-cutaneous syndrome (Stevens-Johnson syndrome) or toxic epidermal necrolysis may occur. Patients should be carefully observed, treatment discontinued and appropriate measures taken, in the event of symptoms such as fever, erythema, blistering, itching, ocular congestion or stomatitis, etc
Other side effects: anaemia, rash, pruritus, sleepiness, insomnia, headache, nausea ang vomiting, anorexia, abdominal pain, diarrhoea, constipation, urinary retention or incontinence.

Drug interactions
There have been reports of disturbances in ocular accommodation occuring after the concomitant use of tolperisone hydrochloride and methocarbamol.

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