Relaxamed (tizanidine): Uses, Dosage & Side Effects

What it's for (Indications)

Tizanidine is primarily indicated for the management of spasticity, a condition characterized by increased muscle tone, exaggerated reflexes, and spasms, which can significantly impair motor function and quality of life.
It is specifically approved for the treatment of spasticity associated with multiple sclerosis (MS) and spinal cord injury.
The therapeutic goal is to alleviate symptoms such as clonus, muscle spasms, and increased muscle tone to improve functional abilities, facilitate activities of daily living (ADLs), and reduce discomfort.
Tizanidine is not indicated for the management of general muscle pain or spasms of rheumatic origin.
Its efficacy in chronic spasticity requires careful titration to balance symptomatic relief with potential dose-dependent side effects.
The clinical benefits include a reduction in frequency and severity of muscle spasms and improved ease of movement, contributing to enhanced patient mobility and care, and thereby improving overall quality of life for individuals severely affected by spasticity.
The treatment aims to provide symptomatic relief to enable greater independence in daily activities.

Dosage Information

Type	Guideline
Standard	Tizanidine is administered orally, with the dosage requiring careful individual titration to achieve optimal therapeutic effect while minimizing adverse reactions. The typical starting dose is 2 mg, taken orally, which can be gradually increased by 2 mg to 4 mg increments at intervals of 1 to 7 days, depending on patient response and tolerability. The usual therapeutic dose range typically falls between 8 mg to 24 mg per day, administered in three to four divided doses. The maximum recommended daily dose is 36 mg. It is important to note that bioavailability can be significantly affected by food; administering tizanidine consistently with or without food is crucial to maintain stable plasma concentrations and avoid fluctuations in drug levels. For patients with renal impairment (creatinine clearance less than 25 mL/min), dosage adjustment is necessary, often requiring a lower starting dose and slower titration due to reduced drug clearance. Similarly, patients with hepatic impairment may also require dosage modifications and careful monitoring of liver function. Abrupt discontinuation of tizanidine should be avoided due to the risk of withdrawal symptoms, necessitating a gradual reduction in dosage over several days to minimize adverse events such as rebound hypertension or tachycardia.

Type

Guideline

Standard

Tizanidine is administered orally, with the dosage requiring careful individual titration to achieve optimal therapeutic effect while minimizing adverse reactions. The typical starting dose is 2 mg, taken orally, which can be gradually increased by 2 mg to 4 mg increments at intervals of 1 to 7 days, depending on patient response and tolerability. The usual therapeutic dose range typically falls between 8 mg to 24 mg per day, administered in three to four divided doses. The maximum recommended daily dose is 36 mg. It is important to note that bioavailability can be significantly affected by food; administering tizanidine consistently with or without food is crucial to maintain stable plasma concentrations and avoid fluctuations in drug levels. For patients with renal impairment (creatinine clearance less than 25 mL/min), dosage adjustment is necessary, often requiring a lower starting dose and slower titration due to reduced drug clearance. Similarly, patients with hepatic impairment may also require dosage modifications and careful monitoring of liver function. Abrupt discontinuation of tizanidine should be avoided due to the risk of withdrawal symptoms, necessitating a gradual reduction in dosage over several days to minimize adverse events such as rebound hypertension or tachycardia.

Safety & Warnings

Common Side Effects

Tizanidine can cause a range of side effects, many of which are dose-dependent.
Common adverse reactions include profound drowsiness, dry mouth (xerostomia), asthenia (weakness), dizziness, fatigue, constipation, and blurred vision.
Other frequently reported effects include flu syndrome, rhinitis, pharyngitis, urinary frequency, speech disorder, insomnia, and nervousness.
More serious, though less common, side effects include significant hypotension, which can manifest as orthostatic hypotension or syncope, especially upon initiation or dose escalation, or when used concomitantly with other hypotensive agents.
Hepatotoxicity, evidenced by elevated liver transaminases, has been reported, necessitating liver function monitoring.
Other concerning adverse events include bradycardia, hallucinations, and other psychiatric symptoms such as anxiety or agitation.
In rare instances, QT prolongation has been observed on electrocardiograms, which could potentially lead to serious arrhythmias.
Abrupt discontinuation, particularly after prolonged use or high doses, can precipitate severe withdrawal symptoms such as rebound hypertension, tachycardia, and hypertonia.
Patients should be thoroughly counseled on these potential side effects and advised to report any concerning symptoms to their healthcare provider promptly to allow for appropriate management or dose adjustment.

Serious Warnings

Black Box Warning: Tizanidine does not carry a formal FDA Black Box Warning. However, several serious warnings are associated with its use, necessitating careful clinical management. **Severe Hypotension** is a significant concern, including orthostatic hypotension and syncope, which can occur at any dose, but are particularly prevalent during initiation, dose escalation, or with concomitant use of other alpha-2 adrenergic agonists or antihypertensive agents. Patients should be thoroughly cautioned about the potential for dizziness, lightheadedness, and falls. **Hepatotoxicity** has been reported with tizanidine use, evidenced by elevations in liver transaminases. Baseline and periodic monitoring of liver function tests are recommended, especially during the initial 6 months of therapy and if symptoms suggestive of liver injury (e.g., nausea, vomiting, dark urine, jaundice) appear. Discontinuation of tizanidine is advised if persistent elevations greater than three times the upper limit of normal occur. **Abrupt Discontinuation** of tizanidine, particularly after chronic use or high doses, must be avoided due to the risk of severe withdrawal symptoms, which can include rebound hypertension, tachycardia, and hypertonia. The dosage should be gradually tapered over several days to minimize these risks. **Drug Interactions** with potent cytochrome P450 1A2 (CYP1A2) inhibitors (e.g., fluvoxamine, ciprofloxacin) are contraindicated, as they markedly increase tizanidine plasma concentrations, leading to severe hypotension and profound sedation. Patients should be advised against driving or operating hazardous machinery due to the common and dose-dependent occurrence of **sedation**.
Tizanidine carries several important warnings that necessitate careful clinical consideration.
**Hypotension** is a significant concern; as an alpha-2 adrenergic agonist, tizanidine can cause dose-dependent reductions in blood pressure, including orthostatic hypotension and syncope.
Patients should be counseled on the risks of dizziness and falls and advised to rise slowly from a sitting or lying position.
Concomitant use with other alpha-2 agonists or antihypertensive medications increases this risk substantially.
**Hepatotoxicity** has been reported, with elevations in liver function tests (LFTs) occurring in some patients.
Baseline LFTs and periodic monitoring (e.
g.
, at 1, 3, and 6 months) are recommended, especially during the initial treatment phase or if symptoms of hepatic injury develop.
Tizanidine should be discontinued if LFTs persist at levels greater than three times the upper limit of normal, or if clinical signs of liver dysfunction appear.
**Sedation** is a prominent side effect that can impair the ability to perform hazardous tasks, such as driving or operating machinery.
This effect is potentiated by alcohol and other central nervous system depressants.
**Abrupt Discontinuation** should be avoided as it can lead to rebound hypertension, tachycardia, and hypertonia; the dosage must be gradually tapered over several days to minimize these severe withdrawal reactions.
**Drug Interactions** are critical, particularly with potent CYP1A2 inhibitors (e.
g.
, fluvoxamine, ciprofloxacin), which can lead to dangerously elevated tizanidine levels and severe hypotension and sedation; concomitant use is contraindicated.
Other CYP1A2 inhibitors (e.
g.
, oral contraceptives, acyclovir) require caution and potential dose adjustment.
Patients with **renal or hepatic impairment** require careful dose adjustments and close monitoring due to altered drug metabolism and excretion.
Rare cases of **QT prolongation** have been reported, warranting caution in patients with existing cardiac conditions (e.
g.
, congenital long QT syndrome) or those on other QT-prolonging drugs.
Close monitoring is crucial throughout therapy.

How it Works (Mechanism of Action)

Tizanidine is classified as a centrally acting alpha-2 adrenergic agonist. Its therapeutic effects in reducing spasticity are primarily mediated through its action at presynaptic alpha-2 adrenergic receptors located within the spinal cord. By binding to and activating these receptors, tizanidine inhibits the release of excitatory amino acids, such as glutamate and aspartate, from presynaptic terminals. This reduction in the release of excitatory neurotransmitters subsequently decreases the excitability of alpha motor neurons, which are responsible for muscle contraction. The net result is a decrease in muscle tone, clonus, and the frequency of muscle spasms, without significantly compromising voluntary muscle strength in many patients, a crucial advantage over some other antispasticity agents. While its primary site of action is at the spinal level, some supraspinal effects may also contribute to its overall antispasticity profile. Tizanidine is thought to enhance presynaptic inhibition of motor neurons by activating inhibitory interneurons, thereby reducing the exaggerated reflexes characteristic of spasticity. Its preferential action on polysynaptic reflex pathways over monosynaptic reflexes helps explain its ability to reduce spasticity without causing widespread paralysis.