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Dantrolene Sodium

Trade Names:
Dantrium
- Capsules 25 mg
- Capsules 50 mg
- Capsules 100 mg

Trade Names:
Dantrium Intravenous
- Powder for Injection 20 mg/vial (approximately 0.32 mg/mL after reconstitution)

Mechanism of Action

Pharmacology

Affects contraction of muscle at site beyond myoneural junction and directly on muscle itself; believed to interfere with calcium release from sarcoplasmic reticulum. Affects CNS, causing drowsiness, dizziness, and generalized weakness.

Pharmacokinetics

Absorption

Absorption is incomplete and slow, but consistent.

Distribution

Significantly protein bound, mostly albumin.

Metabolism

Metabolized in the liver to the major metabolites 5-hydroxy dantrole and an acetylamino metabolite.

Elimination

t _½ is 4 to 8 hr (IV), 9 hr (oral).

Indications and Usage

Control of spasticity associated with spinal cord injury, stroke, cerebral palsy or multiple sclerosis; prophylaxis, treatment and postcrisis therapy of malignant hyperthermia.

Unlabeled Uses

Management of exercise-induced muscle pain, neuroleptic malignant syndrome, heat stroke.

Contraindications

Active hepatic disease; muscle spasm resulting from rheumatic disorders; where spasticity is used to sustain upright posture and balance in locomotion or to obtain or maintain increased function.

Dosage and Administration

PO Initial dose 25 mg q day; increase at 4 to 7 day intervals to 25 mg bid to qid, up to max 100 mg bid to qid if necessary.

PO Initial dose 0.5 mg/kg bid; increase to 0.5 mg/kg tid to qid, then by increments of 0.5 mg/kg, up to 3 mg/kg bid to qid, if necessary. Max 100 mg qid.

PO 4 to 8 mg/kg/day in 3 or 4 divided doses for 1 or 2 days prior to surgery with last dose given 3 to 4 hr before surgery or IV 2.5 mg/kg approximately 75 min before anesthesia. Infused over 1 hr. May repeat during surgery, if needed.

IV 1 mg/kg by continuous rapid push; evaluate and repeat as needed until cumulative total dose is up to 10 mg/kg.

PO 4 to 8 mg/kg/day in 4 divided doses for 1 to 3 days to prevent recurrence. If IV route must be utilized, start with at least 1 mg/kg, as needed.

General Advice

• Ensure good IV site using large peripheral vein; medication is very irritating to tissues.
• Reconstitute powder for IV infusion in 60 mL of sterile water without bacteriostatic agent.
• Shake until solution is clear.

Storage/Stability

Store at room temperature for up to 6 hr. Protect from direct light.

Drug Interactions

Plasma protein binding of dantrolene reduced.

Women receiving these may be at increased risk for hepatotoxicity.

Hyperkalemia and myocardial depression possible.

Plasma protein binding of dantrolene reduced.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Caused by oral administration except where otherwise indicated.

Cardiovascular

Tachycardia; erratic BP; phlebitis.

CNS

Drowsiness; dizziness; weakness; general malaise; fatigue; speech disturbances; seizures; headache; lightheadedness; insomnia, mental depression or confusion; increased nervousness.

Dermatologic

Abnormal hair growth; acne-like rash; pruritus; urticaria (IV); eczematoid eruption; sweating; erythema (IV).

EENT

Visual disturbance, diplopia, alteration of taste.

GI

Diarrhea; constipation; bleeding; anorexia; dysphagia; gastric irritation; abdominal cramps.

Genitourinary

Increased urinary frequency; hematuria; crystalluria; difficult erection; urinary incontinence; nocturia; dysuria; urinary retention.

Hepatic

Hepatitis.

Respiratory

Pleural effusion with pericarditis; pulmonary edema (IV).

Miscellaneous

Myalgia; backache; chills; fever; feeling of suffocation; excessive tearing; thrombophlebitis (IV).

Precautions

Pregnancy

Category C (parenteral).

Lactation

Do not use in nursing women.

Children

Safety in children younger than 5 yr not established.

Hepatic Function

Fatal and nonfatal liver disorders may occur; use drug with caution in patients with pre-existing hepatic impairment and in women and patients older than 35 yr.

Special Risk Patients

Use drug with caution in patients with impaired pulmonary function (especially COPD) or cardiac function.

Photosensitivity

Photosensitization may occur.

Extravasation

Because of the high pH of the IV formulation, prevent extravasation into the surrounding tissue.

IV Dantrolene

IV dantrolene is also associated with the loss of grip strength and weakness in the legs.

Long-term use

Safety and efficacy not established; use only if significant pain or disability is present or nursing care is reduced. Consider carcinogenicity risk and liver damage with long-term use. Discontinue therapy if no benefit within 45 days.

Malignant hyperthermia

Supportive care should be foremost in treatment (ie, concurrent with dantrolene therapy).

Patient Information

• Teach patient and family the name, action, administration, and side effects of dantrolene.
• Emphasize importance of follow-up exams and laboratory work to monitor drug therapy.
• Instruct patient to report these symptoms to health care provider: weakness, malaise, fatigue, nausea, diarrhea, skin rash, itching, bloody or black tarry stools, yellowish discoloration of skin.
• Instruct patient to avoid intake of alcoholic beverages or other CNS depressants.
• Advise patient that drug may cause drowsiness and to use caution while driving or performing other tasks requiring mental alertness.
• Caution patient to avoid exposure to sunlight and to use sunscreen or wear protective clothing to avoid photosensitivity reaction.
• Caution patient that dantrolene may decrease grip strength and increase weakness of leg muscles especially when walking down stairs.
• Advise patients to exercise caution in eating on day of administration because difficulty swallowing and choking is possible.