Dantrolene acts to reduce which of the following in malignant hyperthermia?

• A. Nerve conduction velocity
• B. Muscle rigidity
• C. Blood glucose
• D. Platelet aggregation

Answer: (B)

Dantrolene works by limiting calcium release from the skeletal muscle's sarcoplasmic reticulum, which reduces the calcium available for muscle contraction. In malignant hyperthermia, excessive calcium release causes sustained muscle contraction and a dangerous hypermetabolic state. By lowering intracellular calcium, dantrolene relaxes the muscles and slows the excessive metabolic activity, thereby reducing muscle rigidity. It doesn't directly change nerve conduction velocity, blood glucose, or platelet aggregation, which is why the key effect in this condition is the relief of rigidity.