Muscle Relaxants: List of Common Muscle Relaxers

Muscle relaxers are prescription medications that help regulate muscle contraction (tightening) to reduce pain and discomfort caused by muscle spasms and muscle spasticity (stiffness).

Short-term use of muscle relaxers relieves pain caused by tense or spasming muscles and improves daily functioning.

Muscle relaxers are the third most prescribed medication for low back pain.

When Muscle Relaxers are Prescribed

Muscle relaxers are prescribed when there is severe pain, discomfort, and/or functional disability due to muscle spasms or stiffness. The decision to prescribe a muscle relaxer is based on the following factors: 

• When over-the-counter (OTC) and non-drug therapies (eg, physical therapy, stretching, or heat therapy) are ineffective
• To prevent muscle spasms/stiffness and potential injury following spine surgery or during a physical therapy session
• In addition to OTC pain medication, rest, physical therapy, and other non-drug therapies to relieve discomfort and improve function

The duration of treatment is generally short (2-3 weeks).

Factors that Affect the Type of Muscle Relaxer Prescribed

Choosing a muscle relaxer depends on the cause of the pain (muscle spasms or stiffness, or both). 

Potential side effects and medication interactions, concomitant medical conditions, and personal preferences are also considered.

Types of Prescription Muscle Relaxers

Muscle relaxers are categorized based on their ability to treat stiffness, spasms, or both.

• Antispastic drugs. These medications reduce tightness in the muscle through various mechanisms in the brain and directly within the muscle tissue.
• Antispasmodic drugs. These medications stop the spontaneous or involuntary contraction of muscles (such as jerks, twitches, or cramps) that cause spasms.

Two medications, tizanidine and diazepam, have both antispastic and antispasmodic activity.

How Muscle Relaxers May Be Given

Muscle relaxers are given orally (by mouth) or via an injection, and in rare cases, the drug is delivered directly into the spinal cord through an implanted device.

An oral muscle relaxer is more commonly prescribed because it is convenient to take and does not require needles.

Underlying medical conditions and the severity and expected duration of pain and/or disability may be reasons to consider an injectable form.

Oral administration of muscle relaxers

Oral muscle relaxers are taken by mouth in the form of a tablet or capsule. As the drug moves through the gastrointestinal tract, it is slowly absorbed into the bloodstream and delivered to the brain and other areas of the body.

Intramuscular (IM) administration of muscle relaxers

IM injection involves delivering medication into a large muscle with a lot of blood vessels, such as the thigh or buttock muscle. The medication is slowly absorbed into the bloodstream and then delivered throughout the body.

IM muscle relaxers are typically used in emergency or urgent care settings when a quick onset of action is preferred. They are also used when a person has difficulty swallowing.

Intravenous (IV) administration of muscle relaxers

IV injection delivers the drug through a vein and directly into the bloodstream. This method allows the medication to travel quickly to the brain and other areas of the body and provides quick relief.

Intravenous muscle relaxers are reserved for use in a hospital or other clinical setting.

Intrathecal (IT) administration of muscle relaxers

The intrathecal route involves delivering medication directly into the fluid surrounding the spinal cord, typically through an implanted pain pump. The intrathecal route uses a smaller dose of medication, causing fewer or less intense side effects.

Intrathecal muscle relaxers are generally only used in cases of severe spasticity from an underlying chronic condition such as cerebral palsy.

Common Muscle Relaxers and Their Effects

The following table lists the commonly prescribed muscle relaxers, the types of muscle issues they treat, and the mode of delivery.

Antispasmodic muscle relaxers are more frequently prescribed for back and neck pain compared to antispastics.

When Muscle Relaxers May Be Prescribed for Back and Neck Pain

Muscle relaxers are prescribed when muscle spasms or spasticity are suspected as the cause of the pain, such as in cases of :

• Injury or trauma
• Muscle strain
• Poor posture
• Spinal conditions (eg, scoliosis)
• Neurological conditions (eg, multiple sclerosis and cerebral palsy)
• Nerve inflammation or compression (sciatica)

The effectiveness of muscle relaxers differs for each person. Factors such as the underlying cause of pain and the use of other OTC or non-drug therapies play a role in the overall effectiveness of the treatment.

See 6 Things to Know About Muscle Relaxants

Safety Profile of Muscle Relaxers

Muscle relaxers are generally safe and well-tolerated when used short-term at recommended doses.

Sedation and drowsiness are the most commonly reported side effects, but factors such as underlying conditions and the use of other medications may increase the risk.^-

It is advisable to discuss the potential side effects and risks with a doctor.