dantrolene

REMS

PO: Treatment of spasticity associated with:
Prevention of malignant hyperthermia in patients at high risk.
IV: Emergency treatment of malignant hyperthermia.
Prevention of malignant hyperthermia in patients at high risk.

Unlabeled Use:

Management of moderate to severe neuroleptic malignant syndrome.

Action ⬆ ⬇

Acts directly on skeletal muscle, causing relaxation by decreasing calcium release from sarcoplasmic reticulum in muscle cells.
Prevents intense catabolic process associated with malignant hyperthermia.

Therapeutic effects:

Reduction of muscle spasticity.
Treatment and prevention of malignant hyperthermia.

Pharmacokinetics ⬆ ⬇

Absorption: 35% absorbed after oral administration. IV administration results in complete bioavailability.

Distribution: Widely distributed to tissues.

Metabolism/Excretion: Almost entirely metabolized by the liver.

Half-Life: 8.7–11.4 hr.

Time/Action Profile ⬆ ⬇

(effects on spasticity)

ROUTE	ONSET	PEAK	DURATION
PO	1 wk	unknown	6–12 hr
IV	rapid	rapid	unknown

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Situations in which spasticity is used to maintain posture or balance (PO only);
Lactation: Lactation.

Use Cautiously in:

Cardiac, pulmonary, or previous liver disease;
Women and patients >35 yr (↑ risk of hepatotoxicity);
OB: Use during pregnancy only if potential maternal benefit justifies potential fetal risk;
Geri: Use lowest possible dose in older adults (may have risk of hepatotoxicity).

Adv. Reactions/Side Effects ⬆ ⬇

CV: changes in BP, HF, tachycardia

Derm: flushing, pruritus, sweating, urticaria

EENT: excessive lacrimation, visual disturbances

GI: diarrhea, anorexia, cramps, dysphagia, GI bleeding, HEPATOTOXICITY, nausea, vomiting

GU: crystalluria, dysuria, erectile dysfunction, frequency, incontinence, nocturia

Hemat: anemia, aplastic anemia, eosinophilia, leukopenia, thrombocytopenia

Local: irritation at IV site, phlebitis

MS: myalgia

Neuro: drowsiness, muscle weakness, confusion, dizziness, headache, insomnia, malaise, nervousness

Resp: dyspnea, pleural effusion, respiratory depression

Misc: ANAPHYLAXIS, chills, drooling, fever

Interactions ⬆ ⬇

Drug-drug:

Calcium channel blockers may ↑ risk of cardiovascular collapse; avoid concomitant use
Additive CNS depression with CNS depressants, including alcohol, antihistamines, opioid analgesics, sedative/hypnotics, and parenteral magnesium sulfate.
↑risk of hepatotoxicity with other hepatotoxic agents or estrogens.
↑risk of arrhythmias with verapamil.
↑neuromuscular blocking effects of vecuronium.

Drug-Natural Products:

Concomitant use of kava-kava, valerian, chamomile, or hops can ↑ CNS depression.

Route/Dosage ⬆ ⬇

Spasticity

PO (Adults ): 25 mg once daily for 7 days, then 25 mg 2 times daily for 7 days, then 50 mg 3 times daily for 7 days, then 100 mg 3 times daily; may ↑ to 100 mg 4 times daily, if needed.
PO (Children ≥5 yr): 0.5 mg/kg once daily for 7 days, then 0.5 mg/kg 3 times daily for 7 days, then 1 mg/kg 3 times daily for 7 days, then 2 mg/kg 3 times daily (not to exceed 400 mg/day).

Prevention of Malignant Hyperthermia

PO (Adults and Children ≥5 yr): 4–8 mg/kg/day in 3–4 divided doses for 1–2 days before procedure, with last dose 3–4 hr preoperatively.
IV (Adults and Children ): 2.5 mg/kg given 75 min before surgery.

Treatment of Malignant Hyperthermia

IV (Adults and Children ): At least 1 mg/kg, continued until symptoms ↓ or a cumulative dose of 10 mg/kg has been given. If symptoms reappear, dose may be repeated.

Neuroleptic Malignant Syndrome (unlabeled)

IV (Adults ): 1–2.5 mg/kg initially; if rapid resolution of hyperthermia and rigidity is observed, may follow with 1 mg/kg every 6 hours (max dose = 10 mg/kg/day). After the patient is stabilized and symptoms have resolved, consider taper over days to weeks (do not abruptly discontinue).

Availability ⬆ ⬇

(Generic available)

Capsules: 25 mg; 50 mg; 100 mg
Powder for injection: 20 mg/vial; 250 mg/vial

Assessment ⬆ ⬇

Assess bowel function periodically. Persistent diarrhea may warrant discontinuation of therapy.
Muscle Spasticity: Assess neuromuscular status and muscle spasticity prior to and periodically during therapy to determine response.
Malignant Hyperthermia: Assess previous anesthesia history of all surgical patients. Also assess for family history of reactions to anesthesia (malignant hyperthermia or perioperative death).
- Monitor ECG, vital signs, electrolytes, and urine output continuously when administering IV for malignant hyperthermia.
- Monitor patient for difficulty swallowing and choking during meals on the day of administration.

Lab Test Considerations:

Monitor liver function frequently during therapy. Liver function abnormalities (↑ AST, ALT, alkaline phosphatase, bilirubin, GGT) may require discontinuation of therapy.
- Evaluate renal function and CBC before and periodically during therapy in patients receiving prolonged therapy.

Implementation ⬆ ⬇

PO: If gastric irritation becomes a problem, may be administered with food. Oral suspensions may be made by opening capsules and adding them to fruit juices or other liquids. Drink immediately after mixing.

IV Administration:

Reconstitution: Reconstitute each 20 mg of Dantrium with 60 mL of sterile water for injection (without a bacteriostatic agent). Shake until solution is clear. Solution must be used within 6 hr. Protect diluted solution from direct light.
- Reconstitution: Reconstitute Ryanodex by adding 5 mL of sterile water for injection; do not reconstitute with other solutions. Shake vial to ensure uniform orange suspension. Do not administer solutions that are discolored or contain particulate matter. Solution is stable for 6 hr at room temperature.

Treatment of Malignant Hyperthermia

Administer reconstituted solution without further dilution.
Rate: Administer each single dose by rapid continuous IV push through Y-site. Follow immediately with subsequent doses as indicated. Medication is very irritating to tissues; observe infusion site frequently to avoid extravasation.

Prevention of Malignant Hyperthermia

Rates of products for prevention differ.
Rate: Inject Ryanodex over at least 1 min starting 75 min before surgery into catheter with free-flowing 0.9% NaCl or D5W or into a patent indwelling catheter; flush before and after injection.
Intermittent Infusion: Reconstitute required number of Dantrium vials as above and transfer to a larger volume sterile plastic bag (do not use glass bottles).
Rate: Administer over 1 hr beginning 75 min before anesthesia.

Patient/Family Teaching ⬆ ⬇

Advise patient not to take more medication than the amount prescribed, to minimize risk of hepatotoxicity and other side effects. If a dose is missed, do not take unless remembered within 1 hr. Do not double doses.
- May cause dizziness, drowsiness, visual disturbances, and muscle weakness. Advise patient to avoid driving and other activities requiring alertness until response to drug is known. After IV dose for surgery, patients may experience decreased grip strength, leg weakness, light-headedness, and difficulty swallowing for up to 48 hr. Caution patients to avoid activities requiring alertness and to use caution when walking down stairs and eating during this period.
- Advise patient to avoid taking alcohol or other CNS depressants concurrently with this medication.
- Instruct patient to notify health care professional if rash; itching; yellow eyes or skin; dark urine; or clay-colored, bloody, or black, tarry stools occur or if nausea, weakness, malaise, fatigue, or diarrhea persists. May require discontinuation of therapy.
- Advise patient to wear sunscreen and protective clothing to prevent photosensitivity reactions.
- Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected and to avoid breastfeeding during and for 3 days after last dose. Monitor infants breastfed during therapy for respiratory depression and muscle weakness.
- Emphasize the importance of follow-up exams to check progress in long-term therapy and blood tests to monitor for side effects.
Malignant Hyperthermia: Patients with malignant hyperthemia should carry identification describing disease process at all times.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇