Dantrolene Sodium

Skeletal muscle relaxant for malignant hyperthermia prophylaxis and treatment in horses; prevention of capture myopathy; exertional rhabdomyolysis prevention. Skeletal muscle relaxant. Mechanism: directly inhibits ryanodine receptor (RyR1) in sarcoplasmic reticulum → reduces calcium release → impairs excitation-contraction coupling → skeletal muscle relaxation without affecting cardiac or smooth muscle. Used for malignant hyperthermia (where abnormal RyR1 causes uncontrolled calcium release). Hepatically metabolized; hepatotoxic with chronic use. Key information Hepatotoxic with prolonged use — monitor liver enzymes. Used for malignant hyperthermia and exertional rhabdomyolysis (tying-up) in horses. Oral: administer with food. Injectable: reconstitute with sterile water only. Photosensitive — protect from light.

Oral capsules: Administer orally. May be given with food to improve compliance and reduce GI upset. Administer with food to reduce GI adverse effects. to reduce GI upset. Capsules may be opened and mixed with food. IV (for malignant hyperthermia emergency): reconstitute and administer rapidly IV; repeat doses every 5–10 min as needed. Store at room temperature; protect from light. If a dose is missed Administer as soon as you remember. If it is almost time for the next scheduled dose, skip the missed dose and resume the normal schedule. Never double up doses to make up for a missed one. Administer with food.

Muscle weakness (generalized — dose-dependent; desired effect may be excessive). CNS: sedation, dizziness. GI: vomiting, diarrhea, anorexia. Hepatotoxicity (most serious adverse effect with chronic use — monitor liver enzymes monthly; idiosyncratic fatal hepatitis in humans). Photosensitivity.

For animals Monitor liver enzymes with prolonged use. — hepatotoxicity with prolonged use; monitor liver enzymes monthly. Avoid in patients with hepatic disease. Use with caution in patients receiving calcium channel blockers (risk of cardiovascular collapse with concurrent verapamil). Avoid in pregnant animals. For people handling this medication Wash hands thoroughly with soap and water after handling. Avoid contact with eyes; if contact occurs, flush with water for 15 minutes and seek medical attention. Keep out of reach of children. If accidental ingestion occurs, contact Poison Control (1-800-222-1222). Muscle relaxant — Wash hands thoroughly with soap and water after handling. after handling. Keep out of reach of children. Pregnant women and women of childbearing age should avoid contact. Keep out of reach of children.

Contact your veterinarian. Dantrolene overdose causes excessive muscle weakness, liver toxicity, and respiratory depression. Contact your veterinarian, a veterinary emergency clinic, or the ASPCA Animal Poison Control Center (888-426-4435) immediately. Do not induce vomiting unless specifically directed by a veterinary professional.