Skeletal muscle relaxants: Nursing pharmacology

Definitions & Key takeaways

Skeletal muscle relaxants are a class of medications that are used to reduce muscle spasticity or muscle tension. They are classified into two categories: centrally-acting skeletal muscle relaxants, which work by depressing neuron activity in the CNS; and direct-acting skeletal muscle relaxants, which prevent the release of calcium ions from muscle cells. Centrally-acting muscle relaxants include cyclobenzaprine, methocarbamol, metaxalone, and chlorzoxazone; whereas among direct-acting skeletal muscle relaxants, we have dantrolene.

When caring for a client taking a skeletal muscle relaxant, the nursing considerations should focus on the client's assessment, monitoring for side effects, and pain and discomfort from spasticity. Nursing education to clients includes how to safely self-administer their medication and ways to minimize side effects like sedation, anticholinergic effects, constipation, urinary frequency, or hesitancy.

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Introduction0:00–0:53

Skeletal muscle relaxants are medications that reduce muscle contraction, so they are primarily used to relieve both acute or chronic muscle spasms and spasticity.
Muscle spasms are sudden and involuntary muscle tightness or contractions, and are most often caused by muscle fatigue or injury.
On the other hand, muscle spasticity is a sustained muscle spasm associated with decreased dexterity that originates from the central nervous system, which can occur due to damage to the nerves that coordinate muscle activity, and can also be seen with chronic neurological disorders, such as multiple sclerosis and stroke; as well as in cerebral palsy and spinal cord damage.Now, skeletal muscle relaxants can further be divided into centrally-acting and direct-acting muscle relaxants.

Skeletal muscle relaxants0:53–1:57

Centrally-acting muscle relaxants include cyclobenzaprine, methocarbamol, metaxalone, chlorzoxazone, tizanidine, baclofen, carisoprodol, and orphenadrine.
Other medications can also act as centrally-acting muscle relaxants, such as benzodiazepines, but they’re most commonly used as anxiolytics, sedatives, or anticonvulsants.
On the other hand, direct-acting muscle relaxants include dantrolene.All of these medications can be taken orally. Additionally, methocarbamol can also be administered intravenously or intramuscularly, while dantrolene can be given intravenously, and baclofen can be given intrathecally.Once administered, centrally-acting muscle relaxants act on the neurons of the central nervous system or CNS to interfere with muscle reflexes and decrease the skeletal muscle tone.

Mechanism of action1:57–4:07

Although the exact mechanism by which they act is poorly understood, the site of action of some of these medications is known.
Cyclobenzaprine and methocarbamol primarily act on the brainstem and the spinal cord neurons. Carisoprodol and chlorzoxazone block the nerve conduction in the descending reticular formation in the brain, which is responsible for maintaining muscle tone and posture.
Tizanidine acts by stimulating alpha-2 adrenergic receptors on the presynaptic neurons in the CNS, which decreases the release of norepinephrine in the sympathetic neurons.
Baclofen activates GABAB, receptors in the spinal cord to reinforce the action of GABA, which is an inhibitory neurotransmitter, and decreases the release of the excitatory neurotransmitter, glutamic acid.
Finally, orphenadrine acts by blocking the muscarinic receptors as well as NMDA receptors in the CNS, which interferes with the transmission of nerve impulses from the spinal cord to the muscles.On the other hand, the direct-acting muscle relaxant, dantrolene, enters skeletal muscle cells and prevents the release of calcium ions from the sarcoplasmic reticulum.
Due to its action, dantrolene has a special use in the treatment of malignant hyperthermia, which is caused by certain inhaled anesthetics and succinylcholine in genetically susceptible individuals.
That leads to a massive release of calcium from the sarcoplasmic reticulum, causing excessive muscle rigidity and hyperthermia.
The general side effects of skeletal muscle relaxants are caused by CNS depression, and include drowsiness, dizziness, headaches, and weakness.

Side effects4:07–5:49

There may also be gastrointestinal effects, including anorexia, nausea, vomiting, and constipation. Additionally, depression of other reflex pathways can lead to hypotension and arrhythmias.
In the renal system, there may be urinary frequency and urgency.Regarding specific side effects, orphenadrine and cyclobenzaprine cause anticholinergic side effects, such as dry mouth, blurred vision, tachycardia, urinary retention, and constipation.
Additionally, cyclobenzaprine can cause visual hallucinations. On the other hand, baclofen can cause hyporeflexia, hypothermia, and bradycardia.
In addition, long-term use of baclofen and carisoprodol can lead to tolerance, and therefore require an increased dose to achieve the original response.
Moreover, these result in dependence, causing withdrawal symptoms when discontinued abruptly. Next, chlorzoxazone produces a metabolite that is excreted in the urine, giving it an orange or purplish-red color.
Finally, high doses of dantrolene have a boxed warning for severe hepatotoxicity.As far as contraindications and cautions, dantrolene is contraindicated in clients with hepatic disease.

Contraindications and cautions5:49–7:03

On the other hand, skeletal muscle relaxants, especially metaxalone, tizanidine and cyclobenzaprine, should be used with caution in clients with severe hepatic or renal disease.
Now, the effects of skeletal muscle relaxants on pregnancy and breastfeeding are not clear, but they should generally be avoided as they can cross the placenta and are also secreted into breast milk.
Moreover, they should also be used with caution for clients with a seizure disorder, which can get triggered by the depression and imbalance of the neuronal activity in the brain caused by these medications; and heart disease because they can depress heart muscle activity.
Finally, skeletal muscle relaxants should be avoided in clients taking CNS depressants such as barbiturates, opioids, tricyclic antidepressants, and alcohol, as their depressant effect can add up, resulting in respiratory depression, coma, or even death.Okay, if your client is prescribed a skeletal muscle relaxant, be sure to perform a baseline assessment, focused on pain and mobility of the affected muscles.

Nursing considerations & client education7:03–10:56

Review any diagnostic test results such as X-ray, CT or MRI, as well as laboratory tests like baseline CBC, liver and renal function tests.
Then, explain how the medication will help relieve muscle spasms and pain, and advise them to contact their healthcare provider if their symptoms don’t improve.Now, if your client has experienced a musculoskeletal injury, they could be prescribed a central-acting muscle relaxant like cyclobenzaprine.
Explain that the medication works best when combined with other interventions, such as rest, heat, massage and physical therapy.
Instruct them to take the medication as directed with a glass of water, but if this upsets their stomach they can take it with food or milk.
Next, talk to them about possible side effects they could experience and how to manage them. If they experience drowsiness, caution them to avoid activities that require alertness, such as driving, until they know how the medication affects them; and remind them to avoid alcohol and medicines like cough or cold treatment during treatment, since these can increase drowsiness.
If they experience dizziness, advise them to change positions slowly to avoid injury from falls. And if a dry mouth becomes bothersome, suggest they use sugar-free chewing gum or lozenges, or take frequent sips of water.
Additional side effects, such as constipation and urinary retention can be managed by increasing their consumption of fiber and fluids, as well as emptying their bladder regularly.
Finally, teach your client to contact their healthcare provider if they experience symptoms of liver damage, such as nausea, fatigue, or anorexia; or symptoms of cardiac arrhythmias, such as palpitations or a feeling of a fast heartbeat.
Alright, if your client has chronic muscle spasticity from conditions like multiple sclerosis or spinal cord injury, they can receive baclofen directly into the intrathecal space inside the spinal canal through an implanted pump.
This is a small metal canister that contains a reservoir for the medication, and is surgically implanted under the skin in the lower abdomen.
Attached to the pump is a catheter that delivers the medication into the intrathecal space. When caring for a client with an intrathecal baclofen pump, be sure to monitor them closely for infection at the insertion site.
Ensure they understand the warning signs of getting too much medication, such as increased drowsiness and low muscle tone; or too little medication, such as a sudden return of spasticity, as well as auditory or visual hallucinations, or other psychotic symptoms.
Stress the need to visit their healthcare provider regularly to ensure their equipment is in good working order, as well as to receive medication refills so they won’t run out of it.
Finally, while caring for a client taking a skeletal muscle relaxant, continue to monitor for side effects and for the therapeutic effect of decreased pain and discomfort from spasticity.Alright, as a quick recap ….

Review10:56–12:19

Skeletal muscle relaxants are used to help relieve muscle spasms or spasticity. Centrally-acting skeletal muscle relaxants work by depressing neuron activity in the CNS, whereas direct-acting skeletal muscle relaxants prevent the release of calcium ions from muscle cells.
General side effects include CNS depression, headaches, hypotension and weakness. When caring for a client taking a skeletal muscle relaxant, nursing considerations center around client assessment, as well as continued monitoring for side effects and decreased pain and discomfort from spasticity.
Client education includes how to safely self-administer their medication, and ways to minimize side effects like sedation, anticholinergic effects, constipation, urinary frequency or hesitancy.
For clients receiving intrathecal baclofen, priority nursing considerations include monitoring the insertion site for infection, and providing education about ensuring their equipment is in good working order, and understanding symptoms caused by receiving either too much or