Pharmacology, part 28: Musculoskeletal Medications - Neuromuscular Blocking Agents & Muscle Relaxants

by Cathy Parkes March 23, 2021

In this video

Neuromuscular blocking agents - Succinylcholine and pancuronium

  • Indications
  • Mode of action
  • Tip to remember
  • Side effects
    • Signs and symptoms of malignant hyperthermia
  • Black box warning
  • Administration
  • Interventions

Direct-acting skeletal muscle relaxants - Dantrolene

  • Indications
  • Mode of action
  • Side effects
  • Black box warning
  • Tip to remember
  • What to monitor

Centrally-acting muscle relaxant - Baclofen

  • Indications
  • Mode of action
  • Tip to remember
  • Side effects
  • Patient teaching

Full Transcript

Okay. In this video, we are going to start in on our musculoskeletal medications. If you are following along with cards, I am on card 90. And in this video, we are going to talk about neuromuscular blocking agents as well as muscle relaxants.

Alright. So let's first cover those neuromuscular blocking agents which include medications such as succinylcholine and pancuronium.

These medications are used as an adjunct to anesthesia during surgery or during intubation procedures.

They work by blocking acetylcholine at the neuromuscular junction which results in skeletal muscle paralysis.

So my weirdo way of remembering these medications, if you look at the names, we have succinylcholine and pancuronium. I think of, "Suck it. You can't get to these acetylcholine receptors. I put pans on all of them." And that just helps me remember that these medications really block that acetylcholine.

In terms of side effects, they are serious. They include respiratory arrest, apnea, as well as malignant hyperthermia.

I would definitely be familiar with the signs and symptoms of malignant hyperthermia which include muscle rigidity and fever. Also, following surgery, patients sometimes have muscle pain due to the use of these medications.

This class of medication also carries a black box warning due to the risk of cardiac arrest associated with hyperkalemic rhabdomyolysis.

In terms of key points that you definitely need to keep in mind when administering these medications, if your patient was to end up with malignant hyperthermia, which again, those symptoms are muscle rigidity and fever, then you would want to take the following interventions. You would want to administer oxygen, give the patient dantrolene, which is a key skeletal muscle relaxant, and then provide cooling measures as well.

Alright. Now let's talk about direct-acting skeletal muscle relaxants. The key medication to know within this class is dantrolene, which we actually just mentioned when we were covering neuromuscular blocking agents because dantrolene can be used to treat malignant hyperthermia, and can actually be used to prevent it as well.

And it is also used to reduce muscle spasticity in conditions such as spinal cord injuries, cerebral palsy, and MS.

So the mode of action of dantrolene is that it prevents the release of calcium in the muscles. So this inhibits muscle contractions and decreases muscle spasticity.

Side effects can include drowsiness, muscle weakness, GI upset as well as hepatotoxicity.

So this medication actually carries a black box warning as well due to that risk for hepatotoxicity.

The way I remember this medication, if you look at the word dantrolene, you have Dan and then Trol. So I think, "Dan got run over by a trolley and became a paraplegic, and now he needs dantrolene to treat his muscle spasms." So while your patient is on this medication, because of that risk of hepatotoxicity, definitely monitor their liver enzymes and monitor the patient for signs and symptoms of liver damage.

Okay. Finally, let's talk about a centrally-acting muscle relaxant. The key medication that falls within this class is baclofen.

Baclofen can be used to treat muscle spasticity related to a spinal cord injury to cerebral palsy as well as MS.

It works by enhancing the effect of GABA in the central nervous system which reduces muscle spasticity.

The way I remember this medication is that if you pull out your back, you might need baclofen.

So side effects can include drowsiness, nausea, as well as constipation.

Because it can cause constipation, you definitely want to advise your patient to increase their fluid and fiber intake to help counteract this side effect.

So that is it for this video. When I come back, we will talk about medications that are used for osteoporosis. Thank you so much for watching!


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