tizanidine (Zanaflex)
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Introduction
Tradename: Zanaflex.
Indications
- muscle spasms
- skeletal muscle relaxant used for acute & intermittent management of increased muscle tone associated with spasticity
- treatment of spasticity in patients with multiple sclerosis
Contraindications
- concurrent use of alpha-2 adrenergic agonists
Caution:
- liver disease
- renal disease
- hypotension & patients receiving antihypertensive agents
- cardiac disease
Dosage
- adults: 4-12 mg TID
- maximum of 3 doses in any 24 hour period with maximum daily dose of 36 mg/day
- taper over 7 days when discontinued
Reduce dosage in renal failure & hepatic insufficiency
Tabs: 4 mg.
Monitor
- liver function tests at 1, 3, & 6 months, then periodically[5]
Adverse effects
- common (> 10%)
- hypotension, sedation, daytime drowsiness, somnolence, xerostomia
- less common (1-10%)
- bradycardia, syncope, fatigue, dizziness, anxiety, nervousness, insomnia, pruritus, rash, nausea/vomiting,dyspepsia, constipation, diarrhea, abnormal liver function tests, muscle weakness, tremor
- uncommon (< 1%)
- palpitations, ventricular extrasystoles, psychosis, visual hallucinations, delusions, hepatic failure
- tizanidine is associated with lower incidences of injury & delirium compared to baclofen when used for musculoskeletal pain[7]
- withdrawal symptoms may occur with abrupt discontinuation
- tachycardia, hypertonia[4]
- rebound hypertension (less common than with clonidine)
- NO rebound hypertension when tapered over 7 days
- risk of falls < baclofen, cyclobenzaprine
- drug adverse effects of adrenergic receptor agonists
- drug adverse effects of alpha-adrenergic receptor agonists
- drug adverse effects of sympathomimetic(s)
- drug adverse effects of antihypertensive agents
Drug interactions
- oral contraceptives decrease tizanidine clearance
- increased toxicity with concurrent use of:
- diuretics, other alpha adrenergic agonists, antihypertensives, baclofen, alcohol & other CNS depressants
- coadministration with CYP1A2 inhibitors (fluvoxamine or ciprofloxacin), increases serum concentration of tizanidine & potentiates its hypotensive & sedative effects
- drug interaction(s) of tizanidine with fluvoxamine
- drug interaction(s) of tizanidine with ciprofloxacin
- drug interaction(s) of NSAIDs & antihypertensives
Laboratory
Mechanism of action
- centrally-acting alpha-2 adrenergic agonist
- pharmacologically similar to clonidine
More general terms
- centrally-active alpha-adrenergic receptor agonist
- alpha-2 adrenergic receptor agonist
- skeletal muscle relaxant (tranquilizer)
- antispasmodic
References
- ↑ Kaiser Permanente Northern California Regional Drug Formulary, 1998
- ↑ Department of Veterans Affairs, VA National Formulary
restricted to spinal cord injury, neurology, & rehabilitation. should only be used in failed baclofen cases - ↑ FDA Medwatch http://www.fda.gov/medwatch/safety/2007/safety07.htm#Zanaflex
- ↑ 4.0 4.1 Prescriber's Letter 15(12): 2008 Common Oral Medications that May Need Tapering Detail-Document#: http://prescribersletter.com/(5bhgn1a4ni4cyp2tvybwfh55)/pl/ArticleDD.aspx?li=1&st=1&cs=&s=PRL&pt=3&fpt=25&dd=241208&pb=PRL (subscription needed) http://www.prescribersletter.com
- ↑ 5.0 5.1 Prescriber's Letter 17(7): 2010 Recommended Lab Monitoring for Common Medications Liver Function Test Scheduling Detail-Document#: http://prescribersletter.com/(5bhgn1a4ni4cyp2tvybwfh55)/pl/ArticleDD.aspx?li=1&st=1&cs=&s=PRL&pt=3&fpt=25&dd=260704&pb=PRL (subscription needed) http://www.prescribersletter.com
- ↑ Deprecated Reference
- ↑ 7.0 7.1 Su Zhang VR, Niu F, Lee EA et al Safety of baclofen versus tizanidine for older adults with musculoskeletal pain. J Am Geriatr Soc. 2023 Mar 29 PMID: https://www.ncbi.nlm.nih.gov/pubmed/36989193
- ↑ 8.0 8.1 Hwang YJ, Chang AR, Brotman DJ, Inker LA, Grams ME, Shin JI. Baclofen and the risk of fall and fracture in older adults: A real-world cohort study. J Am Geriatr Soc. 2023 Nov 7. PMID: https://www.ncbi.nlm.nih.gov/pubmed/37933734 https://agsjournals.onlinelibrary.wiley.com/doi/abs/10.1111/jgs.18665