Muscle Relaxants

Hi, and welcome to this video about Muscle Relaxants!

Muscle relaxants are a group of medications that can decrease muscle tone and spasticity, relieving pain and discomfort.

This can be done locally by a group of drugs called neuromuscular blockers, or “centrally” by a group of drugs called spasmolytics (or antispasmodic).

Let’s talk about neuromuscular-blocking agents first.

Neuromuscular blockers affect skeletal muscles by blocking the nerve transmission to the muscle at the neuromuscular junction.

This can be done two different ways; by blocking the nerve transmission to the muscle or nerve reception of the muscle.

Neuromuscular-blocking agents are potent muscle relaxants usually used only during surgery to prevent muscle movement.

Their structure is related to acetylcholine (the main neurotransmitter in the body) and they cause muscle relaxation by binding to acetylcholine receptors.

This blocks neuromuscular transmission and causes the muscle to be paralyzed.

Neuromuscular blocking agents should only be used with anesthesia when artificial ventilation is available.

Examples of neuromuscular blocking agents are: succinylcholine, cisatracurium, mivacurium, doxacurium, and rocuronium

Adverse effects of these drugs may include: prolonged muscle paralysis, muscle weakness, and respiratory insufficiency.

Centrally-acting muscle relaxants are used to suppress muscle spasms, usually from an injury.

The most common treatments are for back pain or neck pain.

These relaxants can also treat muscle spasticity, which is continuous muscle spasms that cause rigidity, tightness, or stiffness.

Conditions that can cause muscle spasticity include multiple sclerosis (MS), cerebral palsy (CP), and amyotrophic lateral sclerosis (ALS).

Centrally-acting muscle relaxants work on the central nervous system to decrease muscle spasms and pain in a variety of ways.

Some inhibit the brain transmission to the muscle that interprets pain, while some cause overall CNS depression to pain sensation.

Some enhance the gamma-Aminobutyric acid effects in the spinal cord.

Gamma-Aminobutyric acid is also responsible for the regulation of muscle tone.

Some of the most commonly used muscle relaxants to treat muscle spasms are: cyclobenzaprine, methocarbamol, chlorzoxazone, and carisoprodol.

Drugs to treat muscle spasticity are baclofen, dantrolene, and diazepam.

The more common side effects of centrally acting skeletal muscle relaxants (SMRs) include: drowsiness, dizziness, headache, nervousness, reddish-purple or orange urine, and lowered blood pressure upon standing.

You should not take muscle relaxants with alcohol, CNS depressant drugs, such as opioids or psychotropics; sleeping medications, or herbal supplements such as St. John’s Wort.

Talk to your doctor about how you can safely use muscle relaxants if you are older than 65 years, have a mental health problem or brain disorder, or have liver problems.
So let’s review. Muscle relaxants have two main categories.

Locally-acting neuromuscular blockers, and centrally-acting skeletal muscle relaxers.

They have two main categories of therapeutic uses:

Neuromuscular-blocking agents are typically used during surgical procedures.

Skeletal muscle relaxers help with two different disorders of muscle – Muscle spasms and muscle spasticity.

Muscle spasms may occur after a back or neck injury.

Muscle spasticity is a condition where muscles spasm continuously, which causes stiffness, rigidity, and pain but is often associated with MS, CP, ALS and similar conditions.

Thanks for watching and happy studying!