Dantrolene sodium is prescribed for a client with flexor spasms. What is the therapeutic action of this medication?

Dantrolene sodium is prescribed for a client with flexor spasms. What is the therapeutic action of this medication?

• A. Inhibits calcium release from SR in smooth muscle
• B. Increases CNS excitability
• C. Blocks acetylcholine at NMJ
• D. Acts directly on the skeletal muscle to relieve spasticity

Answer: (D)

Dantrolene works by acting directly on skeletal muscle to relieve spasticity. It inhibits calcium release from the sarcoplasmic reticulum inside skeletal muscle cells, typically by blocking the ryanodine receptor. With less calcium available, the excitation-contraction coupling is reduced, so actin-myosin interaction decreases and the muscle relaxes. This direct muscle effect distinguishes it from drugs that modify the CNS to reduce spasticity or from those that affect the neuromuscular junction or smooth muscle.

Dantrolene works by acting directly on skeletal muscle to relieve spasticity. It inhibits calcium release from the sarcoplasmic reticulum inside skeletal muscle cells, typically by blocking the ryanodine receptor. With less calcium available, the excitation-contraction coupling is reduced, so actin-myosin interaction decreases and the muscle relaxes. This direct muscle effect distinguishes it from drugs that modify the CNS to reduce spasticity or from those that affect the neuromuscular junction or smooth muscle.