Muscle Relaxants: Types, Uses, and Side Effects

What Are Muscle Relaxants?

Muscle relaxants are prescription medicines used to prevent and reduce muscle spasms and tightness, a condition known as spasticity. These medications work by causing muscles to become less tense or stiff, which in turn reduces pain and discomfort associated with muscle-related conditions. Muscle spasms occur when there is an uncontrolled involuntary contraction of a group of muscles, where the muscles suddenly shorten and contract, often causing significant pain.

Muscle spasms and tightness can result from various conditions, including long-term injuries to the head or back, or they may occur as part of short-term injuries or conditions such as low back pain or whiplash. The primary goal of muscle relaxants is to alleviate the physical discomfort and functional limitations caused by these involuntary muscle contractions.

What Muscle Relaxants Are Available?

Several muscle relaxants are available to prescribe, and they vary in their chemical composition and mechanisms of action. Healthcare providers can choose from a diverse pharmacological group of centrally acting skeletal muscle relaxants that include both antispasticity and antispasmodic medications.

Common Types of Muscle Relaxants

• Baclofen – acts on the central nervous system and is used for various spasticity conditions
• Diazepam – a benzodiazepine that works on the central nervous system
• Tizanidine – acts centrally to reduce muscle tightness
• Methocarbamol – works on the central nervous system to relieve muscle spasms
• Dantrolene – uniquely works directly on the muscle rather than the central nervous system
• Cyclobenzaprine – a skeletal muscle relaxant used for acute muscle pain from strains and sprains
• Carisoprodol – an antispasmodic medication for musculoskeletal conditions
• Chlorzoxazone – a centrally acting muscle relaxant
• Metaxalone – used for acute musculoskeletal conditions
• Orphenadrine – an antispasmodic skeletal muscle relaxant
• Cannabis extract (Sativex®) – containing dronabinol and cannabidiol, available only on the NHS for limited uses

Most muscle relaxant preparations are available as tablets, capsules, or liquids. Baclofen is also available as an intrathecal injection directly into the back for cases requiring more intensive treatment.

How Do Muscle Relaxants Work?

Muscle relaxants employ different mechanisms of action depending on their chemical class. Understanding how these medications work helps explain their varying effectiveness for different conditions and their potential side effects.

Central Nervous System Depressants

Most muscle relaxants act as central nervous system depressants, producing a sedative effect or preventing nerves from sending pain signals to the brain. Medications including baclofen, diazepam, methocarbamol, and tizanidine operate by affecting the central nervous system (brain and spinal cord). These agents work by decreasing muscle spasms through changes in the central nervous system, reducing signals that trigger involuntary muscle contractions.

Direct Muscle Action

Dantrolene differs from other muscle relaxants by working directly on the muscle tissue itself rather than on the central nervous system. This peripheral action mechanism makes dantrolene unique among skeletal muscle relaxants and gives it a distinct pharmacological profile.

Antispastic Mechanisms

Antispastic medications act on the spinal cord or skeletal muscle directly to improve muscle tightness (hypertonicity) and involuntary spasms. This direct action on spinal cord pathways helps restore normal muscle tone in patients with conditions like multiple sclerosis or cerebral palsy.

When Are Muscle Relaxants Prescribed?

Muscle relaxants serve various clinical purposes and are prescribed for both acute and chronic conditions. Healthcare providers prescribe these medications when appropriate, considering patient-specific factors and the underlying condition.

Acute Musculoskeletal Injuries

Muscle relaxants are indicated for acute musculoskeletal conditions including spasms and low back pain. They are commonly used to treat short-term injuries resulting from overstretching during sport or physical exercise, such as strains and sprains. Cyclobenzaprine, for example, is used specifically to relieve pain from muscle spasms caused by acute muscle injuries and is used alongside rest and physiotherapy.

Spasticity Conditions

Healthcare providers mainly prescribe antispastic muscle relaxers to treat spasticity, which is a disruption in muscle movement patterns causing certain muscles to contract all at once when you try to move or even at rest. Spasticity is usually caused by damage to nerve pathways within the brain or spinal cord that control movement and stretch reflexes.

Multiple Sclerosis

Muscle relaxants play a crucial role in managing multiple sclerosis symptoms. Those used in MS treatment include baclofen, tizanidine, gabapentin, diazepam, clonazepam, and dantrolene. Cannabis extract (Sativex®) is available on the NHS only for patients with multiple sclerosis who have tried other muscle relaxants without success.

Other Clinical Applications

Beyond primary indications, muscle relaxants are used off-label for numerous other pain and nonpain conditions. These include fibromyalgia, headaches, painful cramps, myofascial pain syndrome, and cervical or neck pain. Some healthcare providers prescribe muscle relaxants as adjuncts to management of musculoskeletal pain and related conditions. Additionally, diazepam and some other muscle relaxants are sometimes prescribed to treat anxiety and seizures, demonstrating their broader therapeutic applications.

Can I Buy Muscle Relaxants?

Muscle relaxants are prescription-only medications in most jurisdictions. There are no over-the-counter (OTC) muscle relaxants available in the United States or the United Kingdom. However, some over-the-counter medications can help with muscle-related issues, such as muscle soreness, including nonsteroidal anti-inflammatory drugs (NSAIDs) and acetaminophen.

How Should Muscle Relaxants Be Taken?

The appropriate administration of muscle relaxants depends on the specific medication prescribed and the patient’s condition. Different types and brands of skeletal muscle relaxers are available in various forms to accommodate different patient needs and preferences.

Available Forms

• Tablets – the most common oral form
• Capsules – including extended-release formulations for prolonged effect
• Solutions or liquids – for patients who have difficulty swallowing
• Injections – such as baclofen intrathecal injection for severe spasticity

Dosing and frequency should be determined by a healthcare provider based on the individual patient’s needs, the specific medication, and the condition being treated. It is essential to follow prescribed dosing instructions carefully and not adjust doses without medical guidance.

Muscle Relaxant Side Effects

Muscle relaxants have numerous possible side effects, though not everyone experiences them. Most side effects typically improve as the body adjusts to the new medication.

Common Side Effects

Muscle weakness is the most common side effect experienced by most muscle relaxant users. Other frequently reported side effects include:

• Drowsiness and sedation
• Dizziness
• Headache
• Nausea
• Fatigue
• Blurred vision
• Difficulty concentrating

These side effects often diminish over time as the body becomes accustomed to the medication.

Serious Considerations

Clinicians should be vigilant for adverse effects, particularly with long-term use. Some muscle relaxants, particularly certain types, carry addiction potential and are usually prescribed only for brief periods due to this risk. This is especially important for benzodiazepine-based muscle relaxants like diazepam.

Who Cannot Take Muscle Relaxants?

Certain individuals should not take muscle relaxants or should exercise caution when considering these medications. Contraindications and precautions depend on the specific medication and individual patient factors. Healthcare providers should screen patients for:

• Allergies or hypersensitivity to the specific medication or drug class
• Pregnancy and breastfeeding – some muscle relaxants may pose risks to developing fetuses or nursing infants
• Liver disease or hepatic impairment – many muscle relaxants are metabolized by the liver
• Kidney disease or renal impairment – affecting drug clearance
• History of substance abuse or addiction – particularly important for medications with abuse potential
• Certain cardiovascular conditions
• Concurrent use of other medications that may interact with muscle relaxants

Always inform healthcare providers about all medical conditions and current medications before starting a muscle relaxant.

Effectiveness of Long-Term Use

The evidence for long-term use of muscle relaxants varies significantly depending on the condition being treated. A systematic review examining 44 studies with 2,482 participants revealed important findings about long-term efficacy.

Conditions Where Evidence is Strongest

Evidence for effectiveness was strongest when muscle relaxants were used for muscle spasms, painful cramps, and neck pain. These conditions appear to benefit most consistently from long-term muscle relaxant therapy.

Conditions With Equivocal Evidence

For fibromyalgia, low back pain, headaches, and other syndromes, studies showed mixed results with some demonstrating small benefits and others showing no benefit. On balance, research has not definitively supported long-term muscle relaxant use for these conditions, suggesting that for many patients these medications may not provide sustained relief for these chronic pain syndromes.

Clinical Implications

These findings suggest that clinicians should consider deprescribing muscle relaxants if pain-related goals are not being met through their use. Healthcare providers should regularly reassess whether the benefits of continued muscle relaxant therapy justify the risks, particularly with extended treatment periods.

Things to Consider When Taking Muscle Relaxants

Several important considerations can help optimize the safe and effective use of muscle relaxants:

• Duration of Use – Most muscle relaxants are intended for short-term or acute use. Only use long-term if specifically directed by your healthcare provider and when benefits clearly outweigh risks.
• Adjunctive Therapy – Muscle relaxants are most effective when combined with rest, physical therapy, and other treatments rather than used alone.
• Individual Selection – Selection of a specific skeletal muscle relaxant should be individualized to each patient based on their condition, medical history, and medication profile.
• Alternative to NSAIDs – Muscle relaxants may be used as an alternative to nonsteroidal anti-inflammatory drugs in patients at risk of gastrointestinal or renal complications.
• Monitoring – Regular follow-up with healthcare providers is essential to assess effectiveness and monitor for side effects.
• Drug Interactions – Inform all healthcare providers about muscle relaxant use, as these medications can interact with other drugs.
• Operating Machinery – Due to sedative effects, avoid operating heavy machinery or driving until you understand how the medication affects you.
• Alcohol Avoidance – Do not consume alcohol while taking muscle relaxants, as it can increase sedative effects and risks.

Frequently Asked Questions

Q: Are muscle relaxants safe for long-term use?

A: Long-term use of muscle relaxants should only be considered if benefits are clearly demonstrated and risks are acceptable. Evidence for long-term effectiveness is strongest for muscle spasms, painful cramps, and neck pain. For other conditions, effectiveness is less certain, and clinicians may consider deprescribing if goals are not being met.

Q: Can I buy muscle relaxants over the counter?

A: No, there are no over-the-counter muscle relaxants in the United States or United Kingdom. All muscle relaxants are prescription-only medications. However, over-the-counter NSAIDs and acetaminophen can help with muscle-related pain.

Q: What is the difference between antispastic and antispasmodic muscle relaxants?

A: Antispastic medications work directly on the spinal cord or skeletal muscle to improve muscle tightness and involuntary spasms, typically for long-term spasticity conditions. Antispasmodics work through the central nervous system to decrease muscle spasms and are typically used for acute conditions like muscle strains.

Q: Can muscle relaxants be used for fibromyalgia and low back pain?

A: While muscle relaxants are sometimes prescribed off-label for these conditions, research evidence for their long-term effectiveness is mixed. They may provide limited benefit for some patients, but many studies do not demonstrate significant effectiveness for fibromyalgia and chronic low back pain.

Q: What should I do if I experience side effects from muscle relaxants?

A: Most side effects improve as your body adjusts to the medication. However, inform your healthcare provider if side effects persist or are bothersome. Do not stop taking the medication without medical guidance, as your doctor may adjust the dose or switch you to a different medication.

Q: Can muscle relaxants be used with other pain medications?

A: Muscle relaxants are often used as adjuncts to other treatments like rest and physiotherapy. However, inform your healthcare provider about all medications you are taking to avoid dangerous interactions.

Similar Articles

Alarming Rise in Self-Harm in Young People

Alarming Rise in Self-Harm in Young People

Skin Signs Of Non-Accidental Injury: Expert Guide For Clinicians

Lichen Simplex Of The Scrotum: Diagnosis And Treatment

Labial Adhesion In Prepubertal Girls: What Parents Need To Know

Thrush In Men: 5 Signs, Causes, And Treatment Options

Author

Sneha TeteBeauty & Lifestyle Writer

 

Sneha is a relationships and lifestyle writer with a strong foundation in applied linguistics and certified training in relationship coaching. She brings over five years of writing experience to renewcure,  crafting thoughtful, research-driven content that empowers readers to build healthier relationships, boost emotional well-being, and embrace holistic living.

Read full bio of Sneha Tete