Dantrolene (Dantrium, Revonto)

MH Hotline - MHAUS 24-hour hotline: 1-800-MH-HYPER (1-800-644-9737) — available for intraoperative consultation.

Primary indication - treatment and prophylaxis of malignant hyperthermia (MH) — the definitive pharmacologic intervention for MH crisis.

Reconstitution - 20 mg/60 mL sterile water (without bacteriostatic agent) — vigorous shaking required;

MH-susceptible patients - use total IV anesthesia (TIVA) and avoid succinylcholine; prophylactic dantrolene is no longer routinely recommended if trigger avoidance is practiced.

Cardiovascular effects - generally minimal at therapeutic doses; hypotension and cardiac dysrhythmias have been reported, particularly with rapid IV administration or concurrent calcium channel blocker use.

Respiratory muscle weakness - skeletal muscle relaxation extends to respiratory muscles at higher doses — monitor ventilation, especially in spontaneously breathing patients.

Pleural effusion - rare but reported with long-term oral use; less of a concern in acute IV perioperative settings.

Hepatic Impairment - Significant hepatic metabolism necessitates caution in liver disease; accumulation possible with repeated dosing in hepatic impairment

MH cart accessibility - dantrolene must be immediately available wherever triggering agents are used — MHAUS recommends ≥36 vials (720 mg) on hand

DRUG INTERACTIONS

• Calcium channel blockers - IV verapamil + dantrolene = risk of cardiovascular collapse and hyperkalemia.
• Neuromuscular blockers - dantrolene potentiates non-depolarizing NMBAs; expect prolonged neuromuscular blockade.
• Estrogen - concurrent use may increase hepatotoxicity risk.
• CNS depressants - additive CNS depression with sedatives, opioids, and inhaled anesthetics.
  
  SIDE EFFECTS
  
• Muscle weakness - dose-dependent generalized weakness is expected; patients may require ventilatory support post-crisis even as MH resolves.
• Phlebitis - dantrolene is highly alkaline (pH ~9.5) and has poor solubility; use a large-bore peripheral or central line and flush well.
• Drowsiness/dizziness

Absolute - No absolute contraindications when used for life-threatening MH crisis

Relative - Active hepatic disease (chronic oral use), concomitant IV verapamil

Caution - Respiratory compromise (monitor ventilation), concurrent NMBAs, history of hepatic impairment, pregnancy (crosses placenta — use if benefit outweighs risk)

MH Acute Treatment - 2.5 mg/kg rapid IV bolus; repeat q5–10 min until symptoms resolve; max cumulative dose 10 mg/kg (some guidelines allow higher if needed).

Reconstitute in 20 mg/60 mL sterile water (without bacteriostatic agent) — vigorous shaking required;

MH Post-Crisis - 1–2 mg/kg IV q4–6h × 24–48 hours to prevent recurrence

Preoperative Prophylaxis - 2.5 mg/kg IV over 1 hour, 1–1.5 hours before anesthetic induction

blocks ryanodine receptor (RyR1) in skeletal muscle SR, preventing uncontrolled calcium release that drives the MH cascade.

Hepatic; Active metabolite: 5-hydroxydantrolene

Renal