From the Guidelines
Dantrolene is the agent that relieves spasticity in Multiple Sclerosis (MS) patients by impairing calcium (Ca2+) release from skeletal muscle sarcoplasmic reticulum. The mechanism of action of dantrolene involves direct inhibition of calcium release from the sarcoplasmic reticulum to the cytosol during sustained contraction, thereby reversing muscle rigidity and decreasing production of heat 1. Key points about dantrolene include:
- It acts directly on the skeletal muscle
- It is thought to inhibit calcium release from the sarcoplasmic reticulum to the cytosol during sustained contraction
- It reverses muscle rigidity and decreases production of heat 1
- Typically, dantrolene is administered orally at a starting dose of 25 mg once daily, gradually increasing to 25-100 mg three to four times daily as needed and tolerated, with a maximum daily dose of 400 mg. The medication works directly on skeletal muscle by binding to ryanodine receptors (RyR1) in the sarcoplasmic reticulum, preventing calcium release and thereby reducing muscle contraction strength. Common side effects include weakness, drowsiness, dizziness, and occasionally liver dysfunction, so liver function tests should be monitored regularly, especially during the first months of treatment. Dantrolene is often reserved for patients who don't respond adequately to first-line antispasticity medications like baclofen or tizanidine due to its potential for liver toxicity. In the context of MS patients, dantrolene's unique mechanism of action makes it a valuable option for managing spasticity, particularly in cases where other treatments have failed or are not tolerated.
From the FDA Drug Label
In skeletal muscle, Dantrium dissociates the excitation-contraction coupling, probably by interfering with the release of Ca++ from the sarcoplasmic reticulum The answer is D dantrolene because it impairs Calcium (Ca2+) release from skeletal muscle sarcoplasmic reticulum, which helps to relieve spasticity in Multiple Sclerosis (MS) patients 2.
From the Research
Agents for Relieving Spasticity in MS Patients
The question asks about the agent that relieves spasticity in Multiple Sclerosis (MS) patients by impairing Calcium (Ca2+) release from skeletal muscle sarcoplasmic reticulum. The correct answer can be identified by examining the mechanism of action of the listed agents.
Mechanism of Action of Agents
- Dantrolene acts by impairing Ca2+ release from skeletal muscle sarcoplasmic reticulum, which makes it a strong candidate for the correct answer 3, 4, 5, 6.
- Diazepam acts as a muscle relaxant but its primary mechanism is through the enhancement of GABAergic transmission, not by impairing Ca2+ release from skeletal muscle sarcoplasmic reticulum 3, 7, 5.
- Tizanidine is an alpha-2 adrenergic agonist that acts centrally to produce its muscle relaxant effects, not by impairing Ca2+ release from skeletal muscle sarcoplasmic reticulum 3, 7, 5.
- Dalfampridine is a potassium channel blocker used to improve walking in patients with MS, but it does not act by impairing Ca2+ release from skeletal muscle sarcoplasmic reticulum.
Conclusion of Mechanism
Based on the mechanism of action, Dantrolene is the agent that relieves spasticity in MS patients by impairing Ca2+ release from skeletal muscle sarcoplasmic reticulum.