Tizanidine

What is Tizanidine?

Tizanidine is a prescription muscle relaxant that belongs to a class of medications called centrally-acting alpha-2 adrenergic agonists. It is primarily used to treat muscle spasticity associated with conditions such as multiple sclerosis, spinal cord injuries, and other neurological disorders. Unlike some other muscle relaxants, tizanidine works specifically in the central nervous system to reduce muscle tone and spasms.

Uses

Tizanidine is FDA-approved and commonly prescribed for several conditions involving muscle spasticity:

• Multiple sclerosis spasticity: Helps reduce muscle stiffness and spasms that commonly occur with this autoimmune neurological condition
• Spinal cord injury: Manages muscle spasticity resulting from traumatic or non-traumatic spinal cord damage
• Stroke recovery: Assists in managing post-stroke spasticity that can interfere with rehabilitation and daily activities
• Cerebral palsy: Reduces muscle rigidity and spasms in adults with this neurological disorder
• Other neurological conditions: May be prescribed for spasticity associated with brain injuries, amyotrophic lateral sclerosis (ALS), or other central nervous system disorders

How it works

Tizanidine works by activating alpha-2 adrenergic receptors in the spinal cord and brain stem, which reduces the release of excitatory neurotransmitters that cause muscle spasms. This action decreases nerve signals sent to muscles, resulting in reduced muscle tone and spasticity without significantly affecting muscle strength. The medication primarily targets the central nervous system rather than acting directly on muscle tissue.

Side effects

Common side effects include:

Submit Your Paper

• Drowsiness and sedation
• Dizziness
• Dry mouth
• Weakness or fatigue
• Constipation
• Low blood pressure
• Nausea
• Urinary tract infections

Serious side effects to watch for:

• Liver toxicity or hepatitis
• Severe hypotension (dangerously low blood pressure)
• Hallucinations or psychosis
• Severe allergic reactions
• Withdrawal symptoms if stopped abruptly

Warnings and precautions

• Liver function monitoring: Regular liver function tests are required as tizanidine can cause potentially serious liver damage, particularly in women and patients taking higher doses
• Pregnancy and breastfeeding: Classified as pregnancy category C; should only be used if potential benefits justify risks to the fetus, and breastfeeding mothers should consult their healthcare provider
• Kidney impairment: Patients with kidney disease may need dose adjustments as the medication is partially eliminated through the kidneys
• Elderly patients: Older adults may be more sensitive to side effects, particularly sedation and low blood pressure, requiring careful dose titration
• Driving and machinery: Can cause significant drowsiness and dizziness, so patients should avoid driving or operating machinery until they know how the medication affects them

Interactions

Tizanidine has several important drug interactions that can affect its safety and effectiveness:

• Fluvoxamine and ciprofloxacin: These medications significantly increase tizanidine levels and are contraindicated due to risk of severe hypotension and sedation
• Other central nervous system depressants: Alcohol, benzodiazepines, and opioids can enhance sedative effects, increasing risk of excessive drowsiness
• Antihypertensive medications: May cause additive blood pressure lowering effects, potentially leading to dangerous hypotension
• Birth control pills: Oral contraceptives can increase tizanidine levels, requiring potential dose adjustments
• Acetaminophen: May increase acetaminophen levels, though this interaction is generally not clinically significant
• CYP1A2 inhibitors: Medications like fluvoxamine that inhibit this enzyme can dramatically increase tizanidine concentrations
• Alpha-2 agonists: Other medications in this class may have additive effects
• Baclofen: Combining with other muscle relaxants may increase sedation and muscle weakness

Check interactions with the GMJ Interaction Checker

Dosage

Typical adult dosing for tizanidine starts at 2-4 mg every 6-8 hours as needed, with a maximum of three doses in 24 hours initially. The dose may be gradually increased by 2-4 mg per dose every 1-4 days as tolerated, up to a maximum of 36 mg per day divided into three or four doses. Some patients may require doses up to 16 mg per individual dose for optimal effect. Dosage should always be individualized and determined by a healthcare provider based on the patient’s specific condition, response to treatment, and tolerance of side effects. The medication can be taken with or without food, though taking it with food may reduce the peak concentration and some side effects.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

This work is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0). You are free to share and adapt this content with attribution to GMJ News (news.gmj.ge).