THERAPEUTICS

Brands

• Dantrium, Dantamacrin, Dantrolen, Revonto, Ryanodex

Generic?

• Yes

Class

• Muscle relaxant

Commonly Prescribed for

(FDA approved in bold)

• Chronic spasticity

• Malignant hyperthermia (MT)

• Exercise-induced muscle pain

• Heat stroke

• Neuroleptic malignant syndrome

How the Drug Works

• Dantrolene produces relaxation by directly interfering with the release of calcium from the sarcoplasmic reticulum, and weakening muscle contraction. It blocks RYR1 receptors, which show prolonged open state during malignant hyperthermia

How Long Until It Works

• MT: immediate

• Pain: hours to days

If It Works

• Discontinue use once MT symptoms remit. For chronic spasticity, continue to use with standard precautions

If It Doesn't Work

• For spasticity, increase to highest tolerated dose. If ineffective, stop after 45 days and consider alternative treatments. In MT cases, stop all anesthetics

Best Augmenting Combos for Partial Response or Treatment-Resistance

• For focal spasticity, i.e., post-stroke spasticity, botulinum toxin is often more effective and is better tolerated

• Use other centrally acting muscle relaxants with caution due to potential synergistic CNS depressant effect

• 100% oxygen, cold gastric lavage, cooling blankets, and cold IV fluids may be useful in MT

Tests

• Obtain baseline liver function studies then do periodically

ADVERSE EFFECTS (AEs)

How the Drug Causes AEs

• Some are related to CNS depression, others hepatic disease

Notable AEs

• Fatigue, diarrhea, drowsiness, weakness, respiratory failure, rash, labile blood pressure, confusion/depression, abdominal cramps, crystalluria, chills, and fever. Thrombophlebitis (highly irritating to peripheral veins) and extravasation tissue necrosis

Life-Threatening or Dangerous AEs

• Hepatotoxicity is not rare even after only short-term use, especially in patients that are females, over 35, taking multiple medications, or taking dose greater than 800 mg

• Less common: heart failure, pulmonary edema, and hematological abnormalities have been reported

Weight Gain

• Unusual