Pharmacology, part 27: Nervous System Medications - Antiepileptics, Hypnotics/Sedatives & General Anesthetic
by Cathy Parkes March 18, 2021 Updated: December 07, 2022 5 min read
In this article, we cover the most important medications you need to know for seizures, insomnia, and sedatives/general anesthetic. 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!
Antiseizure medications - phenytoin (Dilantin), topiramate (Topamax), levetiracetam (Keppra), primidone (Mysoline)
There are many antiseizure medications available, but the ones we've chosen to cover in this video, article, and in our Pharmacology Flashcards are the most common ones we suspect you will encounter in your pharmacology studies and nursing practice: phenytoin (Dilantin), topiramate (Topamax), levetiracetam (Keppra), primidone (Mysoline). We'll cover common side effects and key administration tips with each.
Phenytoin is an anticonvulsant/antiepileptic medication used to treat and prevent seizures.
Side effects of phenytoin can include gingival hyperplasia, which is an overgrowth of gum tissue, resulting in enlarged gums. Other side effects of phenytoin include vision issues, dizziness, GI upset, and rash.
The therapeutic range for phenytoin is between 10 and 20 mcg/mL. If a patient's phenytoin level is too high, it can result in toxicity, usually of the nervous or cardiovascular system. If a patient's phenytoin level is too low, it will not be effective in preventing seizures, so it's important for the patient to stay in the therapeutic range.
This therapeutic range is somewhat narrow, so patients taking phenytoin will likely need to come in for frequent blood draws to ensure they stay within the therapeutic range. If they are outside of the therapeutic range, their dose may need to be adjusted.
This range is one of the medication ranges covered in our Lab Values Flashcards for Nursing Students!
Topiramate (Topamax) is another anticonvulsant/antiepileptic medication used to treat and prevent seizures.
Topiramate can cause side effects including vision issues, dizziness, and sedation, as well as metabolic acidosis.
Because of the side effect of metabolic acidosis, the patient's bicarbonate levels should be monitored during topiramate therapy. To learn more about expected bicarbonate levels, check out our Arterial Blood Gas Flashcards.
Levetiracetam (Keppra) is another anticonvulsant/antiepileptic medication used to treat and prevent seizures.
Levetiracetam can cause side effects including behavioral abnormalities including suicidal thoughts and confusion. It can also cause agranulocytosis, which is a decrease in white blood cell count, which increases the risk of infection. Other side effects include fatigue, orthostatic hypotension, seizures, sedation, and anticholinergic side effects of dry mouth, blurry vision, constipation and urinary retention.
If you have a patient taking levetiracetam, you will need to monitor their complete blood count (CBC) levels and monitor them for signs of infection.
Primidone is a barbiturate anticonvulsant/antiepileptic medication used to treat and prevent seizures.
Primidone can cause side effects including drowsiness, GI upset, and blood dyscrasias. Examples of blood dyscrasias include anemia, blood cancers such as leukemia, and blood clotting conditions.
The therapeutic range for Primidone is 5 - 12 mcg/mL. Similarly to phenytoin, this narrow range can be tricky for patients to stay within, so they may need to get frequent blood draws to make sure the medication remains effective.
Insomnia medications - Zolpidem (Ambien) and eszopiclone (Lunesta)
Zolpidem and eszopiclone are sedative-hypnotic medications for insomnia (inability to fall or stay asleep).
Mode of action
Both zolpidem and eszopiclone work by increasing GABA (inhibitory amino acid neurotransmitter) in the central nervous system, which helps to promote sedation and sleep.
Zolpidem and esZopiclone help you catch some Z’s...
Side effects with zolpidem and eszopiclone can include daytime sleepiness, which is very common, as well as dizziness, and abnormal thinking and behavior, including a "drugged feeling," unusual dreams, sleep-walking or other unplanned and potentially dangerous sleep activities.
Black box warning
Both zolpidem and eszopiclone carry a black box warning because of the possibility for abnormal thinking and behavior. For example, if a patient drives a car or uses the stove under the influence of this drug, this could have dangerous or injurious consequences.
If you have patients taking zolpidem or eszopiclone, instruct them to make sure that they allow for 8 hours of sleep each night. These medications are designed with an 8-hour period of sleep in mind, so not allowing the full time period may contribute to side effects, such as daytime sleepiness.
Melatonin is another supplement that can be used to help regulate the sleep-wake cycle and may be effective for a patient experiencing insomnia. Melatonin is available over-the-counter.
Barbiturates - pentobarbital (Nembutal), phenobarbital (Luminal)
Barbiturates are a class of medications known as sedative hypnotic agents, and the key medication to know within this class is pentobarbital. Phenobarbital is a similar drug in the same class, though it has different dosage requirements and slower brain penetration.
Pentobarbital can be used for preoperative sedation as well as in the treatment of seizures. It can also help induce a coma in a patient who has high intracranial pressure (ICP).
Intracranial Pressure (ICP)
Intracranial pressure is a measure of pressure inside the skull, including brain tissue and cerebrospinal fluid. The expected range for intracranial pressure is 10-15 mmHg, and this is one of the many lab values covered in our Lab Values flashcards for nursing students.
Increased levels of ICP can be caused by head injury, tumor, meningitis, hydrocephalus, intracranial hemorrhage, or hypertension. Symptoms of increased ICP can include irritability (an early sign), restlessness, headache, decreased levels of consciousness, pupil abnormalities, abnormal breathing and/or posturing.
Mode of action
Pentobarbital and other barbiturates work by increasing GABA, which results in central nervous system depression.
Side effects of barbiturates like pentobarbital include lethargy, hypotension, respiratory depression, as well as constipation. Although they work in similar ways by increasing GABA, barbiturates are known to be more dangerous than benzodiazepines because they cause respiratory depression.
I climbed over barbed wire to get to the pentagon, and the secret service knocked me out with some pentobarbital and took me to jail.
If you have a patient taking pentobarbital, closely monitor their vital signs. Respiratory depression is a side effect of this medication, you will need to make sure there is resuscitation equipment available at the bedside.
General anesthetic agent - propofol (Diprivan)
The key general anesthetic agent you'll need to know for your pharmacology studies and nursing practice is propofol. Propofol is used in the induction and maintenance of general anesthesia.
In 2009, propofol was in the news because Michael Jackson used it in conjunction with benzodiazepines, which resulted in his death.
If you are given propofol, someone will have to prop you up (because you will be knocked out!)
Mode of action
Propofol potentiates the effect of GABA, which results in central nervous system depression.
Propofol can result in side effects like amnesia, bradycardia, hypotension, and respiratory depression. It can be helpful to remember that it slows everything down.
When administering propofol to your patient, ensure that you continuously monitor their vital signs. This is especially important because this medication results in respiratory depression, which can be dangerous.
It's important to remember that propofol does not treat pain -- it has no analgesic effect.
Remember to use or discard unused portions of propofol within 6 hours because of the risk of bacterial contamination with this medication.
Okay. In this video, we are going to recover the remaining nervous system medications. If you are following along with cards, I am on card 86 in our Pharmacology Flashcards, edition 2.
In this video, we will be covering antiseizure medications, medications for insomnia, as well as sedative hypnotic medications, and then general anesthetic agents as well.
Alright. Let's talk about antiseizure medications. There are many antiseizure medications out there. I've chosen 4 of what I feel like are the most common and more important ones to know, to include here on card 86.
So those are phenytoin as well as topiramate, levetiracetam, and primidone. So let's go through some of the common side effects as well as key points regarding administration of these medications.
For phenytoin, a key side effect that you definitely have to know is gingival hyperplasia. So that is basically an overgrowth of gum tissue. The gums become enlarged. Other side effects include vision issues, dizziness, GI upset, as well as a possible rash.
So when a patient is on phenytoin, we are going to need them to come in for frequent blood draws because the therapeutic range for phenytoin is pretty narrow and it's hard to hit it just right with the dose. We don't want to be too high because we'll have toxicity, and we don't want to be too low because it won't be effective. So we're going to need those blood draws pretty frequently to get the dose just right. We want the level to be between 10 and 20 μ/mL.
Then, with topiramate, topiramate can cause side effects such as vision issues, dizziness, and sedation, as well as metabolic acidosis.
Because of that side effect of metabolic acidosis, we're going to want to monitor the patient's bicarbonate levels during therapy.
Then with levetiracetam, this can cause behavioral abnormalities, as well as fatigue and agranulocytosis. So agranulocytosis means it basically causes white blood cell counts to drop, which in turn places the patient at high risk for infection.
So we're definitely going to want to monitor the patient's CBC levels and monitor them for signs of infection.
And then lastly, with primidone. Primidone has side effects such as drowsiness, GI upset, as well as blood dyscrasias.
So with Primidone, this actually has a very narrow therapeutic range as well, just like we had with phenytoin. So again, our patient is going to have to go get frequent blood draws to make sure our dose is just right and within the proper range, which is between 5 and 12 μ/mL.
Alright. Now let's talk about medications that are used for insomnia. Medications that fall within this class include zolpidem, which is Ambien, and eszopiclone, which is Lunesta.
These medications both work by increasing GABA in the central nervous system, which helps to promote sedation and sleep.
So the way I remember these medications is that they both contain Zs. So zolpidem and eszopiclone can help you catch some Zs.
Side effects with both of these medications include daytime sleepiness, which is very common, as well as dizziness, and then possible abnormal thinking and behavior.
So these medications actually carry a black box warning because of the possibility for abnormal thinking and behavior.
So some patient teaching you will want to do, you really want your patient to allow for at least 8 hours for sleep each night.
Also melatonin is another supplement that can be used to help regulate the sleep-wake cycle and may be effective for the patient as well who is dealing with insomnia.
Alright. Now let's talk about barbiturates. Barbiturates are sedative hypnotic agents. And the key medication to know within this class is pentobarbital.
Pentobarbital can be used for preoperative sedation as well as in the treatment of seizures. It can also help to induce a coma in a patient who has high intracranial pressure.
It works by increasing GABA, which results in central nervous system depression.
Side effects include lethargy, hypotension, respiratory depression, as well as constipation.
The way I remember this medication is that, "I climbed over some barbed wire to get into the Pentagon, and the Secret Service came and knocked me out with some pentobarbital and took me to jail." So obviously it didn't happen, but that's my little story on how I remember pentobarbital.
So if your patient is on pentobarbital, you definitely want to closely monitor their vital signs, and you want to make sure that there is resuscitation equipment available at the beside.
Alright. The last nervous system medication that I'm going to go over is a general anesthetic agent which is propofol. Some of you may remember propofol because Michael Jackson used that in conjunction with some benzodiazepines, and that resulted in his death.
Propofol is used in the induction and maintenance of general anesthesia. It also provides sedation for intubated patients.
The mode of action of propofol is to potentiate the effect of GABA, and it results in side effects such as amnesia, bradycardia, hypotension, and respiratory depression. So it brings everything down.
When you are administering propofol to your patient, you're going to want to continuously monitor their vital signs. Also keep in mind that propofol does not treat pain, right? It has no analgesic effect. And then the other thing you need to keep in mind is that you need to use unused portions of propofol within 6 hours because of the risk of bacterial contamination with this medicine.
My way of remembering propofol, it starts with that P-R-O-P like prop. So if you are given propofol, someone will have to prop you up because you will be knocked out. So hopefully that's helpful for you.
That wraps up our nervous system medications. And in my next video, we will start in on musculoskeletal medications. Thanks so much for watching!
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