Pharmacology, part 24: Nervous System Medications - Analgesics: Anticonvulsant, Opioid, Topical & Vascular Headache
by Cathy Parkes March 09, 2021 Updated: December 29, 2021 9 min read
In this article, we cover the most important analgesics and adjuncts you need to know, including anticonvulsants used for neuropathy and fibromyalgia, opioids like oxycodone and morphine, topical analgesics used for numbing, and migraine medications. The Nursing Pharmacology video series follows along with our Pharmacology Flashcards, which are intended to help RN and PN nursing students study for nursing school exams, including the ATI, HESI, and NCLEX.
When you see this Cool Chicken, that indicates one of Cathy's silly mnemonics to help you remember. The Cool Chicken hints in these articles are just a taste of what's available across our Level Up RN Flashcards for nursing students!
Anticonvulsant - pregabalin (Lyrica)
Pregabalin is an anticonvulsant that is used as an adjunct to treat certain types of pain, like neuropathy, fibromyalgia, restless-leg syndrome. As an anticonvulsant, pregabalin is also sometimes used in the treatment of seizures.
Pregabalin prevents Gabby’s neuropathy pain.
Mode of action
Pregabalin works by binding to calcium channels in the central nervous system which decreases the release of excitatory neurotransmitters. Basically, these excitatory neurotransmitters cause the action potential that communicates things like pain or an involuntary movement. To decrease the release of these excitatory neurotransmitters means to decrease those effects.
Pregabalin does not bind to opioid receptors, so it's not classified as an opioid.
Side effects of pregabalin can include drowsiness, dry mouth, dizziness, and possible edema.
If you have a patient on pregabalin, advise them not to consume alcohol. Alcohol is also a central nervous system depressant, so it will exacerbate the side effects of pregabalin. If your patient is planning to discontinue pregabalin, they should do so gradually, because of the risk of withdrawal symptoms like dizziness.
Opioid agonists - Fentanyl, morphine, Dilaudid, oxycodone (Oxycontin)
Opioid agonists are an important class of medication that you need to know for your NCLEX, other nursing exams, and in your nursing practice. Opioids are sometimes referred to as narcotics, and can include fentanyl, morphine, Dilaudid and oxycodone. There are other medications that fall into this category, but those four are the most common and most important ones to be familiar with.
Opioid analgesics like oxycodone are used for moderate to severe pain.
Mode of action
Fentanyl and other opioid analgesics work by binding to opioid receptors in the central nervous system.
There are some very serious side effects associated with opioid agonists like morphine, including respiratory depression (the most important one to know!), sedation, constipation, GI upset, hypotension, and urinary retention.
Black box warning
Oxycodone, fentanyl, morphine and Dilaudid carry a black box warning because of the life-threatening risks associated with respiratory depression, as well as the real risk for abuse and addiction to these medications.
As you probably already know, the United States is facing an opioid overdose epidemic (external link) with the number of opioid overdose deaths increasing each year.
Opioid addiction is a mental health disorder that we cover in our Psychiatric Mental Health Nursing flashcards, including intoxication and withdrawal signs and symptoms, treatment, and key points. We covered one of the treatment options for opioid addiction in this series already, and that is maintenance treatment with methadone or buprenorphine which help reduce withdrawal symptoms and cravings.
When you have a patient taking one of these opioid agonists, it's important to carefully monitor their pain level, their vital signs, and respiratory status.
Patients may be prescribed an opioid for cancer pain, in which case it is often administered around the clock to "get ahead of" that pain.
Opioids delivered via IV should be administered slowly. Patients may ask you to "slam it in," but follow the best practice and do not do that.
The antidote for an opioid overdose (including the opioids covered here as well as a heroin overdose) is naloxone (Narcan). Although there are other opioid antagonists, such as those used in long-term maintenance therapy for opioid addiction, naloxone is the only antidote for acute opioid toxicity! In your nursing career, it is fairly likely that you will need to administer Narcan to a patient someday. Keep in mind that this antidote almost immediately reverses analgesia, which means the pain comes back, and it can also cause hypertension, tachycardia, and agitation.
You may need to RUSH to give naloxone to your patient in response to: Respiratory depression, Urinary retention, Sedation, Hypotension.
Topical analgesic - lidocaine (Xylocaine)
Lidocaine is a topical analgesic, typically used for conditions or procedures involving the skin or mucus membranes, like a wound vac dressing. Lidocaine helps numb the area for patients to make their procedure a little less painful
Mode of action
Lidocaine works by blocking the conduction of pain impulses in a specific area. It blocks sodium channels so that local neurons can't signal the brain regarding sensations.
Side effects of lidocaine are rare. It can cause some stinging or redness at the site of application.
EMLA cream is a lidocaine cream that is often used on pediatric patients. For example, to decrease the pain of an IV insertion on a pediatric pain, you would apply EMLA cream, apply an occlusive dressing, wait one hour, then remove the dressing, clean the area and insert the IV.
For more pediatric best practices, check out our Pediatric Nursing Flashcards.
Vascular headache suppressants - Ergotamine (Ergomar) and sumatriptan (Imitrex)
Ergotamine and sumatriptan are vascular headache suppressants used to treat migraines and cluster headaches.
Migraines and cluster headaches are neurovascular disorders. Migraines cause throbbing head pain that persists for 4-72 hours, and cluster headaches are severe, sudden head pain that lasts 30 minutes - 2 hours, usually at the same time each day. Both of these disorders are covered in our Medical-Surgical Flashcards for nursing students.
Mode of action
The mode of action of ergotamine and sumatriptan is to cause vasoconstriction of the intracranial blood vessels.
A sumo wrestler tripped and sat on my head, ergo it caused vasoconstriction (just like the mode of action of sumatriptan and ergotamine).
Ergotamine carries common side effects like GI upset and hypertension, and sumatriptan can cause dizziness, vertigo, or a warm, tingling sensation.
Black box warning
Both ergotamine and sumatriptan carry black box warnings. They are contraindicated for patients with ischemic coronary artery disease or peripheral vascular disease. If your patient already has trouble getting blood flow to their heart or extremities, further vasoconstriction could be dangerous.
Sumatriptan is also contraindicated for anyone with severe hypertension for the same reason, the last thing we need is further vasoconstriction increasing this patient's blood pressure!
For patients who may take ergotamine or sumatriptan for migraines, you can provide some patient teaching to help with migraines. Advise your patient to lay down in a dark, quiet place to help with their symptoms. These patients should also avoid alcohol, and foods that are rich in tyramine, which can sometimes trigger migraines. If you recall from our lesson on MAOIs, foods that are rich in tyramines are the "finer things," e.g.: aged cheeses, smoked meats, avocado, red wine, chocolate.
In this video, we will continue talking about analgesics. Specifically, we'll be talking about an anticonvulsant that is used as an analgesic. We'll talk about opioid analgesics as well as topical analgesics. And then, finally, we'll discuss vascular headache suppressants.
So let's first talk about an anticonvulsant that is used to treat certain types of pain. Pregabalin or brand name Lyrica is a medication that is used to treat neuropathy as well as fibromyalgia, restless-leg syndrome, and it is also sometimes used in the treatment of seizures.
So the way I remember this medication, if you look at the word pregabalin, it helps to prevent Gabby's neuropathic pain. That's just how I remember what it's for.
So the mode of action of pregabalin is that it binds to calcium channels in the central nervous system which decreases the release of excitatory neurotransmitters. It does not bind to opioid receptors.
Side effects can include drowsiness, dry mouth, dizziness, and possible edema.
If your patient is on pregabalin, you want to advise them to not consume alcohol because that is also a CNS depressant, so it will really exacerbate the side effects of pregabalin. Also, if they are planning to discontinue pregabalin, they should do so gradually.
Now, let's talk about opioid agonists. So this is a very important class of medication that you need to know as a nurse for your NCLEX and for your nursing exams. If you're following along with cards, I'm on card 74, and you definitely need to know the information that is on the back of this card. So let's talk about which medications fall within this class. It includes fentanyl, morphine, Dilaudid as well as oxycodone, and there are others as well, but those are four really important ones that I would be familiar with.
These medications are used for moderate to severe pain and they work by binding to opioid receptors in the CNS.
There are some very serious side effects associated with opioid agonists. This includes respiratory depression, which is probably the most important one to know as well as sedation, constipation, GI upset, hypotension, and urinary retention.
Opioid analgesics do carry a black box warning because of the life-threatening risk for respiratory depression as well as the risk for abuse and addiction to these medications.
So when your patient is on an opioid analgesic, you're going to want to very carefully monitor their pain level, their vital signs as well as their respiratory status.
If your patient is getting this for cancer pain, you really want to administer it around the clock to kind of get ahead of that pain. You're going to administer these medications slowly through the IVs. You're not going to just slam it in there. Even though some of your patients may ask you to do that, you're not going to do that. You're going to administer slowly.
Keep in mind that the antidote for opioid analgesics is naloxone or Narcan. When you give a patient naloxone, which you will, in all likelihood, have to do at some point as a nurse, keep in mind that this will reverse analgesia and it also can cause hypertension, tachycardia as wall as agitation.
So my one tip on remembering some of the key side effects with this medication is that you may need to RUSH to give naloxone to your patient who is taking an opioid analgesic in response to Respiratory depression, Urinary retention, Sedation, and Hypotension. So you need to RUSH. And then, the R is respiratory depression, U is urinary retention, S is sedation, H is hypotension, and that will help you remember at least those four key side effects.
Now, let's talk about a topical analgesic which is lidocaine. Lidocaine can be used for conditions or procedures involving the skin or mucus membranes. I actually use it pretty often at work when I do painful wound vac dressing changes at the hospital. So the lidocaine kind of helps numb the area for the patients to make that procedure a little less painful.
Lidocaine works by blocking the conduction of pain impulses in a specific area.
Side effects are usually pretty rare. It can include a little bit of stinging or erythema at the site of application.
One medication that contains lidocaine is EMLA cream. So this is used a lot in the pediatric population. So if you want to try to decrease the pain with an IV insertion, you can apply EMLA cream and then apply an occlusive dressing over top of that, wait one hour, and then when you're getting ready to do the procedure, you would remove that dressing and then thoroughly clean the area before doing the IV insertion.
Okay. So the last type of analgesics that I want to go over are vascular headache suppressants. Medications that fall within this class include ergotamine and sumatriptan.
These medications are used to treat migraine headaches as well as cluster headaches.
And the mode of action which is important to know, is that they cause vasoconstriction of the intracranial blood vessels.
So the way I remember this mode of action is I think of a sumo wrestler that trips and sits on my head, which causes vasoconstriction of the blood vessels in my head—probably cause a lot more damage, too, but we're going to stick with the vasoconstriction. So that just helps me to remember that sumatriptan causes that vasoconstriction.
In terms of side effects, ergotamine carries common side effects such as GI upset and hypertension, and then, sumatriptan causes dizziness and vertigo as well as a warm, tingling sensation.
Both of these medications do have black box warnings and they would be contraindicated for patients who have ischemic coronary artery disease or peripheral vascular disease, which means, basically, if your patient is having trouble getting blood flow to their heart or to their extremities, we don't really want to do vasoconstriction because that will just decrease blood flow to those areas.
For your patients with migraines, you want to also provide some important teaching, so you should advise them to lay down in a dark, quiet place to help with symptoms.
They should also avoid alcohol and foods that are rich in tyramines as that can sometimes trigger migraines. So if you recall, foods that are rick in tyramines are all those yummy foods, like, aged cheeses, smoked meats, avocado, red wine, chocolate, that type of thing. So they really should avoid those because they can sometimes be triggers for migraines.
In my next video, we will go over medications that are used to treat glaucoma. So definitely hang in there with me and we'll get through these meds together!
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