Myonal

Eperisone HCl.

Each tablet contains 50 mg of eperisone hydrochloride.
Physicochemistry: Nonproprietary name: Eperisone Hydrochloride (JAN); Eperisone (INN).
Chemical name: (2RS)-1-(4-Ethylphenyl)-2-methyl-3-piperidin-1-ylpropan-1-one monohydrochloride.
Molecular formula: C₁₇H₂₅NO·HCl.
Molecular Weight: 295.85.
Melting Point: About 167°C (decomposition).
Eperisone hydrochloride occurs as a white, crystalline powder. It is freely soluble in water, in methanol and in acetic acid (100), soluble in ethanol (99.5).
A solution of eperisone HCl in methanol (1 in 100) shows no optical rotation.
Excipients/Inactive Ingredients: Carnauba wax, carmellose, hydrated silicon dioxide, microcrystalline cellulose, titanium oxide, stearic acid, calcium stearate, sucrose, talc, precipitated calcium carbonate, corn starch, white shellac, hydroxypropylcellulose, pullulan, povidone and macrogol 6000.

Pharmacotherapeutic Group: For improvement of myotonic symptoms.
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 actions (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: Cervical syndrome, Periarthritis of the Shoulder, Lumbago: In open labeled 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 Palsy: Patients (>18 years) with moderate to severe spastic palsy were eligible in the double-blind, randomized study; they received eperisone 300 mg/day or baclofen 60 mg/day for 6 weeks. The results suggest that eperisone 300 mg/day is as effective and well-tolerated as oral baclofen. However, eperisone might be associated with some additional clinical benefits when compared with baclofen.
In a randomized, placebo-controlled, double-blind, three-way cross-over study, patients (18-75 years) with spastic palsy received three consecutive treatment cycles: eperisone 150 mg/day, eperisone 300 mg/day or placebo for 8 weeks. Every treatment period lasted for 14 days. The reduction in the intensity of spasticity versus the beginning of each treatment cycle was significant with eperisone 300 mg/day (p=0.004).
The results of these studies could overall suggest that eperisone 300 mg/day is effective and well-tolerated in the treatment of spastic palsy of different etiologies.
Pharmacokinetics: Blood Concentration: Eperisone hydrochloride was administered orally to 8 healthy adult male volunteers at a single dose of 150 mg/day (a single dose of 150 mg is not approved) 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 1.6-1.9 hr, the peak plasma concentration (C_max) was 7.5-7.9 ng/mL, elimination half-life (t_½) was 1.6-1.8 hr, and the area under the plasma concentration-time curve (AUC) was 19.7-21.1 ng·hr/mL. The plasma concentration profiles of eperisone hydrochloride determined at days 8 and 14 did not significantly vary from those of the 1st day. (See Figure.)

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Muscle relaxant. For improvement of myotonic symptoms such as in cervical syndrome, periarthritis of the shoulder, lumbago, etc.
Spastic paralysis caused by the following diseases: Cerebrovascular disorders, spastic spinal paralysis, cervical spondylosis, sequela of trauma (spinal and head injury), spinal vascular disorders and other encephalomyelopathies.

Muscle relaxant: The usual adult dosage is 1 tablet three times a day (150 mg of eperisone hydrochloride) after meals.
The dosage may be adjusted depending on the patient's age and symptoms.
Spastic Paralysis: The usual adult dose is 1-2 tablets orally, three times a day (150-300 mg of eperisone hydrochloride) after meals.
The dose may be adjusted depending on the patients' age and severity.

Patients with a history of hypersensitivity to any of the 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 Pregnancy & Lactation: 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.]
It is advisable to avoid the administration of MYONAL to nursing mothers. When MYONAL must be used, breastfeeding should be discontinued during treatment.
[It has been reported that Myonal is excreted in breast milk in an animal study (in rats).]
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.

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.]
It is advisable to avoid the administration of MYONAL to nursing mothers. When MYONAL must be used, breastfeeding 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 re-examination period.)
Clinically significant adverse reactions (incidence unknown): Shock and anaphylactoid reactions: Since shock, and anaphylactic shock, and anphylaxis may occur, patients should be carefully observed. In the event of symptoms eg, redness, itching, urticaria, edema of the face or other parts and dyspnea etc, treatment should be discontinued and appropriate measures 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.
Others adverse reactions: See Table 1.

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Precautions for Co-Administration (MYONAL should be administered with care when coadministered with the following drugs.) (See Table 2.)

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MYONAL should be stored at room temperature not exceeding 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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