Dantrolene - oral


Concise Prescribing Info
Indications/Uses
Listed in Dosage.
Dosage/Direction for Use
Adult : PO Severe chronic spasticity Initial: 25 mg once daily, then gradually increase at 7-day interval over approx 7 wk. Max: 400 mg/day. Prophylaxis of malignant hyperthermia 4-8 mg/kg/day in 3-4 divided doses 1-2 days prior to surgery, w/ the last dose given approx 3-4 hr prior to surgery. IV Malignant hyperthermia Initial: 1 mg/kg, may repeat dose if necessary to a total dose of 10 mg/kg. Prophylaxis of malignant hyperthermia 2.5 mg/kg starting approx 75 min prior to surgery.
Dosage Details
Intravenous
Malignant hyperthermia
Adult: Initially, 1 mg/kg via rapid inj, repeat dose if necessary to a total dose of 10 mg/kg.
Child: Same as adult dose.

Intravenous
Prophylaxis of malignant hyperthermia
Adult: 2.5 mg/kg over at least 1 min or 1 hr (depending on product used), starting approx 75 min prior to surgery. Individualised doses may be given intraoperatively if signs of malignant hyperthermia develop.
Child: Same as adult dose.

Oral
Severe chronic spasticity
Adult: Initially, 25 mg once daily, then increase gradually at 7-day interval over approx 7 wk. Max: 400 mg daily. Suggested increment regimen: 25 mg once daily, 25 mg tid for 7 days, then 50mg tid for 7 days, and then 100 mg 3 or 4 times daily. If no further benefit observed w/ the higher dose level, dose should be decreased to the previous level; discontinue if no evident benefit w/in 45 days.
Child: >5 yr Initially, 0.5 mg/kg once daily for 7 days, followed by 0.5 mg/kg tid for 7 days, then 1 mg/kg tid for 7 days, and then 2 mg/kg 3 or 4 times daily. Max: 400 mg daily. If no further benefit observed w/ the higher dose level, dose should be decreased to the previous level; discontinue if no evident benefit w/in 45 days.

Oral
Prophylaxis of malignant hyperthermia
Adult: 4-8 mg/kg daily in 3-4 divided doses 1-2 days prior to surgery, w/ the last dose given approx 3-4 hr prior to surgery.
Hepatic Impairment
Oral:
Contraindicated.
Administration
May be taken with or without food.
Reconstitution
Reconstitute by adding 60 mL of sterile water for inj in a vial labelled as containing 20 mg to provide a soln containing 0.33 mg/mL.
Incompatibility
Incompatible w/ bacteriostatic water for inj, dextrose 5% and NaCl 0.9% inj, and other acidic soln.
Contraindications
Acute muscle spasm, patients who use their spasticity to maintain posture or function, hepatic impairment (oral). Lactation.
Special Precautions
Patient w/ history of liver disease; severe CV impairment due to myocardial disease; obstructive pulmonary disease. Female, patients >35 yr old. Childn. Pregnancy.
Adverse Reactions
Significant: Muscle weakness (e.g. weakness in the legs, loss of grip strength, dyspnoea, resp muscle weakness, dysphagia), photosensitivity (oral).
Nervous: Drowsiness, dizziness, headache, mental depression, confusion, nervousness, insomnia, seizure.
CV: Tachycardia, exacerbation of cardiac insufficiency.
GI: Diarrhoea, anorexia, nausea, vomiting, abdominal pain, GI bleeding, constipation.
Resp: Pleural effusion.
Genitourinary: Haematuria, crystalluria, urinary incontinence or retention.
Musculoskeletal: Myalgia.
Ophthalmologic: Visual disturbance.
Dermatologic: Rash, sweating, pruritus.
Others: Weakness, malaise, fatigue, chills, fever.
Potentially Fatal: Rarely, hepatotoxicity (e.g. hepatitis, hepatic failure).
IV/Parenteral/PO: C
Patient Counseling Information
This drug may cause lightheadedness, dizziness, somnolence, and vertigo, if affected, do not drive or operate machinery.
MonitoringParameters
Monitor motor performance and LFT (baseline and periodically thereafter). Monitor vital signs, electrolytes, arterial blood gas, creatine kinase, end tidal CO2/capnography, urine output, urine myoglobin. Monitor cardiac and resp function, and BP (IV).
Overdosage
Symptoms: Muscular weakness, alteration of consciousness (e.g. lethargy, coma), vomiting, diarrhoea, crystalluria. Management: Supportive treatment. Employ gastric lavage immediately. Maintain adequate airway and monitor ECG. Administer large volume of IV fluids in case crystalluria occurs.
Drug Interactions
May cause hyperkalemia and myocardial depression when concomitantly used w/ Ca channel blockers (e.g. verapamil). May potentiate vecuronium induced neuromuscular blockade. Enhanced CNS effects w/ CNS depressants. Increased risk of liver damage if concomitantly used w/ hepatotoxic drugs (e.g. estrogen).
Food Interaction
Enhanced CNS effects w/ alcohol.
Action
Description: Dantrolene, a direct-acting skeletal muscle relaxant, inhibits the release of Ca ion from the sarcoplasmic reticulum leading to decreased response to action potential and decreased muscle contraction.
Pharmacokinetics:
Absorption: Slowly and almost completely absorbed from the GI tract. Time to peak plasma concentration: Approx 5 hr (oral); 1 min (IV).
Distribution: Crosses the placenta and enters breast milk. Volume of distribution: 36.4±11.7 L.
Metabolism: Metabolised hepatically mainly to 5-hydroxydantrolene and via nitro-reduction to amino-dantrolene which is then acetylated to compound F-490. Additionally, may undergo hydrolysis and subsequent oxidation forming nitrophenylfuroic acid.
Excretion: Via urine (79% as 5-hydroxydantrolene, 17% as compound F-490, 4% as unchanged drug) and some in faeces. Elimination half-life: 4-11 hr.
Chemical Structure

Chemical Structure Image

Source: National Center for Biotechnology Information. PubChem Database. Dantrolene, CID=6914273, https://pubchem.ncbi.nlm.nih.gov/compound/Dantrolene (accessed on Jan. 20, 2020)

Storage
Store between 20-25°C. Do not refrigerate or freeze. Protect from light.
MIMS Class
References
Anon. Dantrolene. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 15/11/2016.

Buckingham R (ed). Dantrolene Sodium. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 15/11/2016.

Dantrolene Sodium Capsule (Par Pharmaceutical Inc). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 15/11/2016.

Joint Formulary Committee. Dantrolene Sodium. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. ttps://www.medicinescomplete.com. Accessed 15/11/2016.

McEvoy GK, Snow EK, Miller J et al (eds). Dantrolene Sodium. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com . Accessed 15/11/2016.

Ryanodex Injection, Suspension (Eagle Pharmaceuticals, Inc). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 15/11/2016.

Disclaimer: This information is independently developed by MIMS based on Dantrolene from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to MIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, MIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2020 MIMS. All rights reserved. Powered by MIMS.com
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