Neurology
Skeletal muscle relaxants
Baclofen, tizanidine and related drugs — Reduce muscle spasticity and spasm in conditions such as MS and spinal injury.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
What it is
These muscle relaxants reduce spasticity — the increased muscle tone, stiffness and spasm caused by conditions affecting the brain or spinal cord. They are used to improve comfort, function and care.
How it works
They act on the nervous system rather than the muscle directly: baclofen calms over-active spinal reflexes through GABA pathways, while tizanidine reduces the nerve signals that drive muscle tone. Dialling down these signals relaxes the over-tight muscles.
In practice
In practice these drugs ease the painful stiffness and spasms of spasticity in conditions like multiple sclerosis, cerebral palsy and spinal-cord injury, and they are titrated carefully to balance benefit against side-effects — chiefly drowsiness, weakness and low blood pressure. A genuinely important safety point is that baclofen must not be stopped abruptly: sudden withdrawal (including from a missed intrathecal pump) can cause a serious reaction with high fever, severe rebound spasticity, confusion and, rarely, life-threatening complications — so the dose is tapered. Tizanidine needs attention to the liver and interacts with certain drugs that raise its levels. Because some loss of useful muscle tone can unmask weakness, the dose is matched to function, and patients are warned about sedation and driving.
Examples
Practical use
How to take it & use it well
- Baclofen and tizanidine are used to ease muscle stiffness and spasms, for example in conditions affecting the nervous system; they are usually started low and built up gradually.
- Take them regularly as prescribed; do not suddenly stop baclofen, as abrupt withdrawal can cause serious effects.
- Expect drowsiness, especially at first, so avoid driving or operating machinery until you know how the medicine affects you.
- Tizanidine can affect the liver, so blood tests may be arranged to check liver function.
- Take with or after food if it upsets your stomach, and rise slowly from sitting or lying down as these medicines can lower blood pressure.
- Tell your team before stopping so a planned, gradual reduction can be arranged rather than stopping suddenly.
Common uses
- Spasticity in multiple sclerosis, spinal-cord injury and cerebral palsy
- Painful muscle spasm
- Severe spasticity via intrathecal baclofen (specialist)
Monitoring
- Spasticity benefit versus weakness and sedation
- Blood pressure; liver function with tizanidine
- Safe, gradual dose changes (never abrupt baclofen withdrawal)
Weighing it up
Advantages & disadvantages
Advantages
- Can reduce painful muscle spasms and stiffness, improving comfort and movement.
- May make physiotherapy, daily activities and sleep easier.
- Doses can be tailored and adjusted gradually to balance benefit against drowsiness.
- Useful for spasticity linked to long-term neurological conditions.
Disadvantages
- Drowsiness, dizziness and muscle weakness are common, particularly when starting or increasing the dose.
- Stopping baclofen abruptly can cause withdrawal effects including high temperature, confusion, rebound spasticity and, rarely, seizures.
- Tizanidine can affect the liver and lower blood pressure.
- Too much muscle relaxation can make weakness or unsteadiness worse for some people.
- Effects can build up with alcohol or other sedating medicines.
Key safety principles
What to watch for
- Do not stop baclofen abruptly — withdrawal can cause high fever, severe rebound spasticity and serious complications; taper the dose.
- Drowsiness, muscle weakness and low blood pressure — titrate to balance benefit and function.
- Tizanidine needs liver monitoring and has important drug interactions.
Key interactions
What to avoid or check alongside
- Alcohol and other sedatives such as opioids or benzodiazepines add to drowsiness and can affect breathing.
- Tizanidine combined with certain medicines that slow its breakdown, such as some antibiotics and the antidepressant fluvoxamine, can cause dangerously low blood pressure and excess sedation and should be avoided.
- Blood pressure lowering medicines may have an added effect, increasing the risk of dizziness or fainting.
- Other medicines that cause drowsiness, including some antihistamines, can increase sedation.
Patient & carer advice
- Never stop baclofen suddenly — always reduce it gradually with advice
- These can make you drowsy — take care driving or operating machinery
- Tell us if you feel too weak or unsteady, so the dose can be adjusted
Use with
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Answers
Skeletal muscle relaxants: frequently asked questions
Why must I never stop baclofen suddenly?
Stopping baclofen abruptly can cause a serious withdrawal reaction with high temperature, confusion, rebound muscle stiffness and rarely seizures. If you need to stop, your team will reduce it gradually.
Are these medicines safe to drive on?
They commonly cause drowsiness and dizziness, especially at first. Do not drive or operate machinery until you know how the medicine affects you, and it is an offence to drive when impaired.
Why might I need blood tests on tizanidine?
Tizanidine can affect the liver, so liver function blood tests may be arranged before and during treatment to make sure it is being tolerated safely.
Can I drink alcohol with muscle relaxants?
Alcohol adds to the drowsiness and dizziness these medicines cause and can make you very sedated. It is best avoided or kept to a minimum, and check with your pharmacist.
What if a dose makes me too weak or sleepy?
Tell your prescriber, as the dose may need adjusting. Do not stop baclofen on your own; a planned, gradual reduction is safer.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
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