Eperisone

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. ⁸⁾

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. ⁸⁾

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. ^8,9)

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). ^10,11)

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. ^12-15)

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. ¹⁶⁾

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. ¹⁷⁾

Blood concentration eperisone 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 determined at days 8 and 14 did not significantly vary from those of the first day. ¹⁾

Note) A single dose of 150 mg is unapproved.