Myonal

Eperisone hydrochloride.

Each white, sugar-coated tablet contains 50 mg of eperisone hydrochloride.
(See Table 1.)

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Excipients/Inactive Ingredients: It contains carnauba wax, carmellose, microcrystalline cellulose, titanium oxide, stearic acid, calcium stearate, sucrose, talc, precipitated calcium carbonate, corn starch, white shellac, hydroxypropylcellulose, pullulan, povidone K30, macrogol 6000 and hydrated silicon dioxide as inactive ingredients.

Pharmacology: Skeletal muscle relaxation: Inhibition of experimentally-induced muscle rigidity: Eperisone hydrochloride suppresses intercollicular section induced decerebrate rigidity (γ-rigidity) and ischemic decerebrate rigidity (α-rigidity) in rats dose-dependently.
Suppression of spinal reflexes: In spinal cats, eperisone hydrochloride suppresses mono- and poly-synaptic reflex potentials induced through spinal nerve efferent root stimulation to a similar degree.
Reduction of muscle spindle sensitivity via γ-motor neurons: Eperisone hydrochloride suppresses the activity of afferent nerve fibers (Ia fibers) from human muscle spindles at 20 min after administration. Eperisone hydrochloride suppresses the spontaneous discharge of γ-motor neurons, but does not act directly on muscle spindles in animals. Accordingly, eperisone hydrochloride reduces muscle spindle sensitivity via the γ-motor neurons.
Vasodilatation and Augmentation of blood flow: Vasodilatory action: Eperisone hydrochloride dilates the blood vessels due to Ca⁺⁺-antagonistic action (in guinea pigs) on the vascular smooth muscle and muscular sympatholytic activity (in humans).
Augmentation of blood flow: Eperisone hydrochloride increases the volume of blood flow in skin, muscle, external and internal carotid arteries and vertebral arteries in humans, monkeys and dogs.
Analgesic action and inhibition of the pain reflex in the spinal cord: When eperisone hydrochloride is perfused into the spinal cord of rats, a tail pinch-induced pain reflex is suppressed, but the reflex returns with the withdrawal of eperisone hydrochloride. This suggests that eperisone hydrochloride possesses an analgesic action at the spinal cord level.
Facilitation of voluntary movement: When eperisone hydrochloride is used in the treatment of spastic paralysis in patients with cerebral apoplexy, it improves the cybex torque curve and electromyogram and facilitates voluntary movements, such as extension and flexion of the extremities, without reducing the muscular force.
Clinical Studies: Neck-shoulder-arm syndrome, scapulohumeral periarthritis and low back pain: In open labeled clinical trials and a double blind controlled clinical trial undertaken to determine the effects of MYONAL on myotonic symptoms associated with these diseases, an efficacy rate of 52.1% (234/449) was achieved. (When fairly effective responses are included, the efficacy rate was as high as 80.4 %.)
Spastic paralysis: In open labeled clinical trials and a double blind clinical trial, the usefulness of MYONAL has been established for spastic paralysis associated with diseases such as cerebrovascular disturbances, spastic spinal paralysis or cervical spondylosis. Improvement rates for rigidity and stiffness in patients with spastic paralysis were 42.3% (197/466) and 45.1% (174/386), respectively.
Pharmacokinetics: Blood concentration: Eperisone hydrochloride was administered orally to 8 healthy adult male volunteers at a single dose of 150 mg/day^note) for 14 consecutive days and the plasma concentration was determined at days 1, 8 and 14. The time to reach the peak plasma concentration (t_max) ranged from 1.6 to 1.9 hr, the peak plasma concentration (C_max) was 7.5 to 7.9 ng/mL, elimination half-life (t_1/2) was 1.6 to 1.8 hr, and the area under the plasma concentration- time curve (AUC) was 19.7 to 21.1 ng・hr/mL. The plasma concentration profiles of eperisone hydrochloride determined at days 8 and 14 did not significantly vary from those of the first day. (See figure.)

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Improvement of myotonic conditions caused by the following diseases: Neck-shoulder-arm syndrome, scapulohumeral periarthritis and low back pain.
Spastic paralysis caused by the following diseases: Cerebrovascular disorders, spastic spinal paralysis, cervical spondylosis, sequelae of surgical trauma (including cerebrospinal tumor), sequelae of trauma (spinal injury and head injury), amyotrophic lateral sclerosis, infantile cerebral palsy, spinocerebellar degeneration, spinal vascular disorder, subacute myelo-optico neuropathy (SMON) and other encephalomyelopathies.

The usual adult dosage for oral use is 3 tablets (150 mg of eperisone hydrochloride) daily in three divided doses after meals.
The dosage may be adjusted depending on the patient's age and symptoms.

MYONAL is contraindicated in the following patients: Patients with a history of hypersensitivity to any ingredients of MYONAL.

Careful Administration (MYONAL should be administered with care in the following patients): Patients with a history of drug hypersensitivity.
Patients with hepatic function disorder.
[MYONAL may aggravate hepatic function.]
Important Precautions: 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.
Use in Children: Safety in children has not been established (insufficient clinical experience).
Use in the Elderly: Since the elderly often have a physiological hypofunction, it is advisable to take measures, such as reduction in dosage under careful supervision.

Use During Pregnancy: MYONAL should only be used in pregnant women or women suspected of being pregnant, if the expected therapeutic benefits are evaluated to outweigh the possible risk of treatment.
[The safety of MYONAL in pregnant women has not been established.]
Use During Lactation: It is advisable to avoid the administration of MYONAL to nursing mothers. When MYONAL must be used, breast feeding should be discontinued during treatment.
[It has been reported that MYONAL is excreted in breast milk in an animal study (in rats).]

Adverse reactions were reported in 416 of 12,315 patients (3.38%).
(At the end of the reexamination period).
Clinically significant adverse reactions (incidence unknown): Shock and anaphylactoid reactions: Since shock and anaphylactoid reactions may occur, patients should be carefully observed. In the event of symptoms such as redness, itching, urticaria, edema of the face or other parts and dyspnea etc., treatment should be discontinued and appropriate measures should be taken.
Oculo-muco-cutaneous syndrome (Stevens-Johnson syndrome) and toxic epidermal necrolysis (Lyell syndrome): Serious dermatopathy such as oculo-muco-cutaneous syndrome (Stevens-Johnson syndrome) or toxic epidermal necrolysis (Lyell syndrome) 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 adverse reactions: (See Table 2.)

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Precautions for coadministration (MYONAL should be administered with care when coadministered with the following drugs.) (See Table 3.)

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MYONAL should be stored below 30°C.
MYONAL should be protected from moisture after opening package.

Muscle Relaxants

M03BX09 - eperisone ; Belongs to the class of other centrally-acting muscle relaxants.

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