What is the mechanism of action of dantrolene?

• A. Inhibition of calcium channels
• B. Antagonizes RYRs on sarcoplasmic reticulum
• C. Inhibition of muscle contraction
• D. Blocking neuromuscular transmission

Answer: (B)

Dantrolene's mechanism of action involves antagonizing ryanodine receptors (RYRs) on the sarcoplasmic reticulum. These receptors play a crucial role in the release of calcium ions during muscle contraction. By inhibiting RYRs, dantrolene decreases calcium release from the sarcoplasmic reticulum into the cytoplasm of muscle cells. This reduction in intracellular calcium levels leads to decreased muscle contraction, making it effective in conditions characterized by excessive muscle activity, such as malignant hyperthermia and spastic disorders.

In contrast, inhibiting calcium channels pertains to a different class of drugs that affect calcium influx, which is not the specific action of dantrolene. While it may seem similar, inhibition of muscle contraction is more of a consequence of dantrolene’s action rather than its direct mechanism of action. Blocking neuromuscular transmission refers to a different mechanism involving the interruption of neurotransmitter action at the neuromuscular junction, which is not applicable to dantrolene’s pharmacological effects.