FDA Box Warning
Drug may be hepatotoxic and should be used only for recommended conditions. Daily doses of 400 mg are less likely to cause fatal and nonfatal hepatitis than daily doses above 800 mg. Overt hepatitis is most common during months 3 and 12, but may occur at any time; females, patients older than age 35, and those receiving concurrent therapy are at higher risk. Use only in conjunction with liver monitoring. Monitor liver function at baseline and regularly during therapy. Discontinue drug if values are abnormal.
Use lowest possible effective dose. If no benefit occurs after 45 days, discontinue.
Relaxes skeletal muscle by affecting excitation-contraction coupling response at site beyond myoneural junction, probably by interfering with calcium release from sarcoplasmic reticulum
Capsules: 25 mg, 50 mg, 100 mg
Powder for injection: 20 mg/vial
Indications and dosages
➣ Chronic spasticity resulting from upper motor neuron disorders, such as multiple sclerosis, cerebral palsy, or spinal cord injury
Adults: Initially, 25 mg P.O. daily, increased gradually in 25-mg increments, if needed, up to 100 mg two or three times daily, to a maximum dosage of 400 mg P.O. daily. Maintain dosage level for 4 to 7 days to gauge patient response.
Children: Initially, 0.5 mg/kg P.O. daily for 7 days, increased to 0.5 mg/kg P.O. t.i.d. for 7 days; then 1 mg/kg P.O. t.i.d. for 7 days; then 2 mg/kg t.i.d., as needed. Don't exceed 100 mg P.O. q.i.d.
➣ Malignant hyperthermic crisis
Adults and children: Initially, 1 mg/kg by I.V. push, repeated as needed up to a cumulative dosage of 10 mg/kg/day
➣ To prevent or minimize malignant hyperthermia in patients who require surgery
Adults and children: 4 to 8 mg/kg P.O. daily in three or four divided doses for 1 to 2 days before surgery; give last dose 3 to 4 hours before surgery. Or 2.5 mg/kg I.V. infused over 1 hour before anesthestics are given.
➣ To prevent recurrence of malignant hyperthermic crisis
Adults: 4 to 8 mg/kg daily P.O. in four divided doses for up to 3 days after initial hyperthermic crisis
• Heat stroke
• Neuroleptic malignant syndrome
• Active hepatic disease (oral form)
• Patients who use spasticity to maintain posture or balance (oral form)
Use cautiously in:
• cardiac, hepatic, or respiratory dysfunction or impairment
• women (especially pregnant women)
• adults older than age 35
• children younger than age 5.
• For I.V. use, add 60 ml of sterile water for injection to each vial; shake until solution is clear. Protect from direct light and use within 6 hours.
• Give therapeutic or emergency dose by rapid I.V. push. Administer followup dose over 2 to 3 minutes.
• Prevent extravasation when giving I.V. Drug has high pH and causes tissue irritation.
CNS: dizziness, drowsiness, fatigue, malaise, weakness, confusion, depression, insomnia, nervousness, headache, light-headedness, speech disturbances, seizures
CV: tachycardia, blood pressure fluctuations, phlebitis, heart failure
EENT: double vision, excessive tearing
GI: nausea, vomiting, diarrhea, constipation, abdominal cramps, GI reflux and irritation, hematemesis, difficulty swallowing, anorexia, GI bleeding
GU: urinary frequency, dysuria, nocturia, urinary incontinence, hematuria, crystalluria, prostatitis
Hematologic: aplastic anemia, leukopenia, thrombocytopenia, lymphocytic lymphoma
Musculoskeletal: myalgia, backache
Respiratory: suffocating sensation, respiratory depression, pleural effusion with pericarditis
Skin: rash, urticaria, pruritus, eczemalike eruptions, sweating, photosensitivity, abnormal hair growth
Other: altered taste, chills, fever, edema
Drug-drug. CNS depressants: increased CNS depression
Estrogen: increased risk of hepatotoxicity
Verapamil (I.V.): cardiovascular collapse (when given with I.V. dantrolene)
Drug-diagnostic tests. Alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, bilirubin, blood urea nitrogen: increased values
Drug-behaviors. Alcohol use: increased CNS depression
Sun exposure: phototoxicity
• Obtain baseline liver function test results; monitor periodically during therapy.
• Monitor ECG, serum electrolytes, and urine output regularly.
With long-term oral therapy, monitor patient for signs and symptoms of hepatotoxicity. Be prepared to discontinue drug if these occur.
• Assess for muscle weakness, poor coordination, and reduced reflexes before and during therapy. Drug may weaken muscles and impair ambulation.
Instruct patient receiving prolonged oral therapy to immediately report weakness, malaise, fatigue, nausea, rash, itching, severe diarrhea, bloody or black tarry stools, or yellowing of skin or eyes.
• Inform patient that drug may cause drowsiness, dizziness, or light-headedness.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and behaviors mentioned above.
ClassificationTherapeutic: skeletal muscle relaxants
- Spinal cord injury,
- cerebral palsy,
- multiple sclerosis.
Time/action profile (effects on spasticity)
|PO||1 wk||unknown||6–12 hr|
Adverse Reactions/Side Effects
Central nervous system
- drowsiness (most frequent)
- muscle weakness (most frequent)
Ear, Eye, Nose, Throat
- excessive lacrimation
- visual disturbances
- pleural effusions
- respiratory depression
- changes in BP
- heart failure
- hepatotoxicity (life-threatening)
- diarrhea (most frequent)
- GI bleeding
- erectile dysfunction
- aplastic anemia
- irritation at IV site
- anaphylaxis (life-threatening)
Drug-Drug interactionAdditive 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.Concomitant use of kava-kava, valerian, chamomile, or hops can ↑ CNS depression.
Availability (generic available)
- Assess bowel function periodically. Persistent diarrhea may warrant discontinuation of therapy.
- Muscle Spasticity: Assess neuromuscular status and muscle spasticity before initiating 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, GGTP) may require discontinuation of therapy.
- Evaluate renal function and CBC before and periodically during therapy in patients receiving prolonged therapy.
Potential Nursing DiagnosesImpaired physical mobility (Indications)
Acute pain (Indications)
Risk for injury (Side Effects)
- Oral: 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.
- Oral dose for spasticity should be divided into 4 doses/day.
- Oral dose is not indicated for neuroleptic malignant syndrome.
- pH: No Data.
- Diluent: Reconstitute each 20 mg with 60 mL of sterile water for injection (without a bacteriostatic agent). Shake until solution is clear. Solution must be used within 6 hr. Administer without further dilution. Protect diluted solution from direct light.Concentration: 0.333 mg/mL.
- Rate: Administer each single dose by rapid continuous IV push through Y-tubing or 3-way stopcock. Follow immediately with subsequent doses as indicated. Medication is very irritating to tissues; observe infusion site frequently to avoid extravasation.
- Intermittent Infusion: Prophylactic dose has been administered as an infusion.
- Rate: Administer over 1 hr before anesthesia.
- Y-Site Compatibility: acyclovir, paclitaxel, palonosetron
- Y-Site Incompatibility: alemtuzumab, alfentanil, amikacin, aminophylline, amphotericin B colloidal, amphotericin B lipid complex, ampicillin, ampicillin/sulbactam, anidulafungin, argatroban, arsenic trioxide, ascorbic acid, atracurium, atropine, azathioprine, aztreonam, benztropine, bivalirudin, bleomycin, bumetanide, buprenorphine, butorphanol, caclium chloride, calcium gluconate, carmustine, caspofungin, cefoperazone, cefotaxime, cefotetan, cefoxitin, ceftazidime, ceftriaxone, cefuroxime, chloramphenicol, chlorpromazine, cisplatin, clindamycin, cyanocobalamin, cyclosporine, dactinomycin, daptomycin, dexamethasone, diazepam, diazoxide, digoxin, diltiazem, diphenhydramine, dobutamine, docetaxel, dopamine, doxorubicin liposome, doxycycline, enalaprilat, ephedrine, epinephrine, epoetin alfa, ertapenem, erythromycin, esmolol, etoposide, etoposide phosphate, famotidine, fenoldopam, fentanyl, fluconazole, fludarabine, folic acid, foscarnet, furosemide, ganciclovir, gemcitabine, gentamicin, glycopyrrolate, granisetron, haloperidol, heparin, hetastarch, hydralazine, hydrocortisone, hydromorphone, hydroxyzine, idarubicin, imipenem/cilastatin, indomethacin, insulin, irinotecan, isoproterenol, ketorolac, labetalol, leucovorin, lidocaine, linezolid, lorazepam, magnesium sulfate, mannitol, mechlorethamine, meperidine, metaraminol, methyldopate, methylprednisolone, metoclopramide, metoprolol, metronidazole, midazolam, milrinone, mitoxantrone, morphine, multivitamins, mycophenolate, nafcillin, nalbuphine, naloxone, nesiritide, nitroglycerin, nitroprusside, norepinephrine, octreotide, ondansetron, oxacillin, oxaliplatin, oxytocin, pamidronate, pancuronium, pantoprazole, papaverine, pemetrexed, penicillin G, pentamidine, pentazocine, pentobarbital, phenobarbital, phentolamine, phenylephrine, phenytoin, phytonadione, piperacillin/tazobactam, potassium acetate, potassium chloride, procainamide, prochlorperazine, proimethazine, propranolol, protamine, pyridoxime, ranitidine, sodium acetate, sodium bicarbonate, streptokinase, succinylcholine, sufentanil, tacrolimus, teniposide, theophylline, thiamine, thiotepa, ticarcillin/clavulanate, tigecycline, tirofiban, tobramycin, tolazoline, trimethoprim/sulfamethoxazole, vancomycin, vasopressin, vecuronium, verapamil, vinblastine, vinorelbine, voriconazole, zoledronic acid
- 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.
- 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.
- Relief of muscle spasm in musculoskeletal conditions. One wk or more may be required to see improvement; if there is no observed improvement in 45 days, the medication is usually discontinued.
- Prevention of or decrease in temperature and skeletal rigidity in malignant hyperthermia.