Dantrolene sodium
Dantrolene sodium (Dantrium)
Dantrolene sodium
( DAN-troh-leen)
Pregnancy Category: C (parenteral use) Dantrium Dantrium IV (Rx)

Classification: Muscle relaxant, centrally acting

See Also: See also Skeletal Muscle Relaxants, Centrally Acting .

Action/Kinetics: Not related to other skeletal muscle relaxants. Acts directly on skeletal muscle, probably by dissociating the excitation-contraction coupling mechanism as a result of interference of release of calcium from the sarcoplasmic reticulum. This results in a decreased force of reflex muscle contraction and a reduction of hyperreflexia, spasticity, involuntary movements, and clonus. Effectiveness in malignant hyperthermia is due to an inhibition of release of calcium from the sarcoplasmic reticulum. This results in prevention or reduction of the increased myoplasmic calcium ion concentration that activates the acute catabolic processes associated with malignant hyperthermia. Absorption is slow and incomplete, but consistent. Peak plasma levels: 4-6 hr. t 1/2: PO 9 hr after a dose of 100 mg; t 1/2: IV 4-8 hr. Significant plasma protein binding.

Uses: PO: Muscle spasticity associated with severe chronic disorders, such as multiple sclerosis, cerebral palsy, spinal cord injury, and stroke. Preoperatively to prevent or reduce the development of signs of malignant hyperthermia. To prevent recurrence following a malignant hyperthermia crisis. IV: Malignant hyperthermia due to hypermetabolism of skeletal muscle. Preoperatively or postoperatively to prevent or reduce the development of signs of malignant hyperthermia in susceptible clients. Investigational: Exercise-induced muscle pain, heat stroke, and neuroleptic malignant syndrome.

Contraindications: Orally in active hepatitis or cirrhosis, where spasticity is used to sustain upright posture and balance in locomotion or to obtain or maintain increased function, and to treat skeletal muscle spasm due to rheumatic disease. Pregnancy, lactation, or children under 5 years of age.

Special Concerns: Use with caution in clients with impaired pulmonary function, especially those with obstructive pulmonary disease; severely impaired cardiac function due to myocardial disease; and a history of previous liver disease or dysfunction.

Side Effects: Following PO use: Side effects are dose-related and decrease with usage. Fatal and nonfatal hepatotoxicity. CNS: Drowsiness, dizziness, weakness, malaise, lightheadedness, headaches, insomnia, seizures, speech disturbances, fatigue, confusion, depression, nervousness. GI: Diarrhea (common), anorexia, constipation, GI bleeding, dysphagia, gastric irritation, abdominal cramps. Musculoskeletal: Backache, myalgia. Dermatologic: Rash (acne-like), photosensitivity, pruritus, urticaria, hair growth, sweating, eczematoid eruption. CV: BP changes, phlebitis, tachycardia. GU: Urinary retention, increased urinary frequency, urinary incontinence, hematuria, crystalluria, nocturia, impotence. Ophthalmic: Visual disturbances, diplopia. Miscellaneous: Chills, fever, tearing, feeling of suffocation, alteration of taste, pleural effusion with pericarditis.
Following IV use: Pulmonary edema, thrombophlebitis urticaria, erythema.

Overdose Management: Symptoms: Extension of side effects. Treatment: Immediate gastric lavage. Maintain airway and have artificial resuscitation equipment available. Large quantities of IV fluids to prevent crystalluria. Monitor ECG.

Drug Interactions: Clofibrate / Plasma protein binding of dantrolene CNS depressants / CNS depression Estrogens / Risk of hepatotoxicity Warfarin / Plasma protein binding of dantrolene

How Supplied: Capsule: 25 mg, 50 mg, 100 mg; Powder for injection: 20 mg

Dosage
?Capsules Spastic conditions.
Adults, initial: 25 mg once daily; then, increase to 25 mg b.i.d.-q.i.d.; dose may then be increased by 25-mg increments up to 100 mg b.i.d.-q.i.d. (doses in excess of 400 mg/day not recommended). Pediatric: initial, 0.5 mg/kg b.i.d.; then, increase to 0.5 mg/kg t.i.d.-q.i.d.; dose may then be increased by increments of 0.5 mg/kg to 3 mg/kg b.i.d.-q.i.d. (doses should not exceed 400 mg/day).
Malignant hyperthermia, preoperatively.
Adults and children: 4-8 mg/kg/day in three to four divided doses 1-2 days before surgery with the last dose given 3 to 4 hr before surgery.
Postmalignant hyperthermic crisis.
Adults and children: 4-8 mg/kg/day in four divided doses for 1-3 days.
?IV Infusion Malignant hyperthermia, crisis treatment.
Adults and children, initial: 2.5 mg/kg 60 min prior to surgery and infused over 1 hr. Additional IV dantrolene may be given during anesthesia and surgery, depending on symptoms.
?IV Push Malignant hyperthermia, crisis treatment.
Initial: At least 1 mg/kg; continue administration until symptoms decrease or a cumulative dose of 10 mg/kg has been administered.