Muscle Relaxant — Alpha-2 Agonist Pregnancy: The safety of tizanidine in pregnancy has not been established — it should not be used in pregnant women unless the benefit clearly outweighs the risk. The safety in breast-fed infants is not known and tizanidine and/or its metabolites have been found in rodent milk, so it should not be used in nursing mothers unless the benefit clearly outweighs the risk (§4.6).

Tizanidine

Brand names: Zanaflex

Tizanidine is a centrally acting muscle relaxant used to relieve spasticity associated with multiple sclerosis or spinal cord injury and disease.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Spasms of the skeletal muscles: 2–4 mg three times daily (in severe cases an extra dose of 2–4 mg may be given, preferably late in the evening to reduce the sedative effect). Spasticity due to neurological disorders: the initial daily dose should not exceed 6 mg in 3 divided doses, increased in steps of 2–4 mg at intervals of half or a full week; the optimum therapeutic response is usually achieved with a daily dose of between 12 and 24 mg, divided into 3–4 equal doses throughout the day

Route: Oral

Frequency: Three times daily (skeletal muscle spasm); 3–4 divided doses throughout the day (spasticity due to neurological disorders)

Max: 36 mg daily — the total daily dose should not exceed 36 mg

Tizanidine has a narrow therapeutic index and high inter-patient variability in plasma concentrations, so the dose must be adjusted individually. A low starting dose of 2 mg three times daily can reduce the risk of side effects; increase gradually and with caution according to individual need and therapeutic response. Paediatric population: safety and efficacy in children and adolescents under 18 years have not been established, only limited data are available, and tizanidine cannot be recommended in this age group. Elderly: experience is limited — the starting dose should be as low as possible and increased in small increments according to tolerability and efficacy. Hepatic impairment: contraindicated in severe hepatic impairment; use with caution in mild and moderate impairment with the lowest possible starting dose and small increments. Liver function tests should be monitored monthly for the first four months in patients receiving doses of 12 mg and higher, and in patients who develop symptoms suggestive of hepatic dysfunction; discontinue if SGPT and/or SGOT are persistently above three times the upper limit of normal, or if hepatitis or jaundice occurs. Discontinuation: decrease the dose slowly (2 to 4 mg per day), particularly in patients who have received high doses (20 to 28 mg daily) for long periods (9 weeks or more) or who are on concomitant narcotics, to prevent or reduce rebound hypertension, tachycardia and hypertonia.

Dose adjustments

Renal

In patients with renal impairment (CLcr < 25 mL/min) treatment should be started with 2 mg once daily with slow titration to achieve the effective dose; dosage increases should be in increments of no more than 2 mg according to tolerability and effectiveness. If efficacy has to be improved, slowly increase the once-daily dose before increasing the frequency of administration. Renal function should be monitored as appropriate, and patients monitored closely for dry mouth, somnolence, asthenia and dizziness as indicators of potential overdose (§4.2/§4.4).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients
Severe hepatic impairment
Concomitant use with potent CYP1A2 inhibitors such as fluvoxamine or ciprofloxacin

Side effects

Somnolence and drowsiness (very common/common)
Dizziness and fatigue (common)
Dry mouth (very common) and gastrointestinal disturbances, nausea (common)
Hypotension and decreased blood pressure (common); bradycardia (uncommon)
Increased hepatic enzymes (common); hepatitis and hepatic failure reported post-marketing
Muscular weakness (common)

Interactions

Potent CYP1A2 inhibitors (e.g. fluvoxamine, ciprofloxacin) — contraindicated (§4.3/§4.4)
Other (moderate or weak) CYP1A2 inhibitors — hypotension, bradycardia or excessive drowsiness can occur; concomitant use should be avoided unless the necessity for tizanidine is clinically evident, in which case use with caution (§4.4). US labelling lists zileuton, amiodarone, mexiletine, propafenone, verapamil, cimetidine, famotidine, oral contraceptives, aciclovir and ticlopidine as examples (US label §7.2)
Antihypertensive therapy and other alpha-2-adrenergic agonists — increased risk of hypotension; monitor blood pressure (§4.4; US label §5.1/§7.5)
Alcohol and other CNS depressants — additive sedative effects (US label §5.3/§7.4)
Potentially hallucinogenic substances, e.g. antidepressants — hallucinations reported with tizanidine have invariably occurred in patients concurrently taking such substances (§4.8)
Concomitant narcotics — increased risk of withdrawal reactions when tizanidine is stopped; taper the dose slowly (§4.4)

Clinical monograph

How it works

It is an alpha-2 adrenergic agonist that reduces excitatory interneurone activity in the spinal cord, decreasing the release of excitatory amino acids and thereby lowering muscle tone.

Prescribing in practice

It is contraindicated with potent CYP1A2 inhibitors such as fluvoxamine and ciprofloxacin, which can dramatically raise its levels and cause profound hypotension and sedation.
Hypotension, drowsiness and dry mouth are common, and it should be withdrawn gradually to avoid rebound hypertension and tachycardia.
Hepatotoxicity can occur, so liver function should be checked where clinically indicated.

Monitoring

Monitor blood pressure, sedation and liver function, particularly during dose titration.

Counselling the patient

Rise slowly from sitting or lying, as the medicine can lower blood pressure and cause dizziness.
Do not stop it suddenly and avoid alcohol, which adds to drowsiness.

Evidence & guidelines

Its efficacy in reducing spasticity is supported by randomised controlled trials in multiple sclerosis and spinal cord disorders.

Reference: NICE NG109 (Spasticity); MHRA Tizanidine Drug Interaction Warning; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Pathways