Pharmacology, part 23: Nervous System Medications - Acetaminophen, NSAIDs & Aspirin
by Cathy Parkes March 04, 2021 Updated: January 26, 2022 9 min read
In this article, we cover non-opioid analgesics, which are common meds used for pain and fever like aspirin, ibuprofen, and acetaminophen (Tylenol). 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!
All of the medications in this article work by inhibiting prostaglandin synthesis in one way or another. So what is prostaglandin synthesis?
Prostaglandins are hormones created at the site of injury or infection, and they can promote inflammation, blood flow, and fever. Prostaglandin synthesis is kicked off by COX enzymes (COX-1 and COX-2).
Inhibiting either the COX enzymes or the prostaglandin synthesis itself will result in a reduction of pain, fever, and inflammation.
Antipyretic - acetaminophen (Tylenol)
The main antipyretic medication you will encounter is one you are probably already familiar with: acetaminophen (Tylenol). Antipyretics are anti-fever medications. Pyretic means fever, which you can remember if you think of the Greek root pyr, which means fire (e.g., pyromaniac or pyrotechnics).
Want to be able to easily identify more medical terms by their roots, suffixes and prefixes? We created our Medical Terminology flashcards to make breaking down words into their parts easy, so you never have to be confused by an unfamiliar word on an exam!
Acetaminophen is used to treat mild to moderate pain and reduce fever.
Mode of action
Acetaminophen works by inhibiting prostaglandin synthesis in the central nervous system.
Acetaminophen does not have many side effects, though it can cause hepatotoxicity (liver toxicity) if consumed in large doses.
Acetaminophen's risk of hepatotoxicity is serious enough that it carries a black box warning. Hepatotoxicity is serious because it can lead to liver failure or even death.
The important patient teaching to remember for acetaminophen is also related to its potential to cause hepatotoxicity. When a patient is taking acetaminophen, it is important that they not exceed 4 grams per day.
Limiting acetaminophen consumption to 4g per day may not always be as straightforward as it sounds. Patients might not just be taking Tylenol, they may also be taking something for a cold, and those products often contain acetaminophen as well. It's important for your patient to pay attention to all sources of acetaminophen to avoid exceeding 4g per day.
Very young/very old patients may have an even smaller daily max dose, like 2 or 3g. Four grams is the max dose in a healthy young adult!
The antidote for acetaminophen overdose is acetylcysteine, a medication otherwise used for pulmonary disorders that have thick mucus secretions.
Fun fact: acetylcysteine smells like rotten eggs! This is an expected finding and not an indication that it has expired.
NSAIDs - Ibuprofen (Advil, Motrin, Excedrin), naproxen (Aleve), ketorolac (Toradol), indomethacin (Indocin)
Non-steroidal anti-inflammatory drugs (NSAIDs, pronounced en-seds) include ibuprofen, naproxen, ketorolac, and indomethacin. NSAIDs are used for mild to moderate pain, fever, or inflammation.
Indomethacin specifically can also be used to help close a patent ductus arteriosus (PDA) in premature babies.
Mode of action
NSAIDS like ibuprofen, naproxen, ketorolac and indomethacin work by inhibiting prostaglandin synthesis, similar to acetaminophen.
What is the difference between acetaminophen and NSAIDs?
Acetaminophen and NSAIDs are similar, as both work to reduce mild to moderate pain and fever, and both work by inhibiting prostaglandin synthesis. The main difference you'll want to remember between acetaminophen and NSAIDS is that NSAIDs help reduce inflammation, while acetaminophen does not.
You might be wondering why acetaminophen does not reduce inflammation like NSAIDs. We don't yet know, but some scientists theorize that acetaminophen interacts with COX enzymes differently than NSAIDs do.
There are more side effects with NSAIDs than there are with acetaminophen. The side effects of NSAIDs can include GI upset, GI bleeding, renal toxicity, a rash, and possible headache. Though it may seem unfortunate that headaches can result from a medication sometimes used to treat headache, some of these "rebound" headaches may occur from medication overuse.
While acetaminophen is hard on the liver, NSAIDs are hard on the kidneys. These should be avoided by any patient with known renal impairment, diseases affecting the kidneys (such as Diabetes Mellitus), or in patients with elevated kidney function labs such as BUN and creatinine.
Important patient teaching to remember for NSAIDs is that if your patient has peptic ulcer disease, or any other bleeding disorder, then NSAIDs are contraindicated because of the risk of GI bleeding; they should not take them.
Peptic ulcer disease is erosion in the mucosa of the stomach, esophagus, or duodenum and is covered in our Med-Surg flashcards!
Unlike other medications, NSAIDs MAY be given with milk or antacids to reduce the risk of injury to the lining of the stomach.
Another patient teaching tip is that if a patient is taking NSAIDs, they should avoid alcohol, because alcohol increases that NSAID's risk of causing GI bleed.
NSAID COX-2 inhibitor - celecoxib (Celebrex)
Another NSAID you'll need to know about is the COX-2 inhibitor celecoxib. Celecoxib can be used for osteoarthritis as well as rheumatoid arthritis.
With celecoxib, you can celebrate without arthritis pain.
Celecoxib selectively inhibits COX-2, as opposed to the main class of NSAIDs in the prior section which are not selective and inhibit both COX-1 and COX-2.
The difference between COX-1 and COX-2 is that COX-1 is continuously produced in the body and plays a role in maintaining gastrointestinal mucosa lining, while COX-2 is not continuously produced, and is produced specifically during an inflammatory response. It's fair to say that Cox-2 inhibitors are more targeted.
Mode of action
Celecoxib works by inhibiting the COX-2 enzyme which decreases prostaglandin synthesis, which in turn causes a decrease in pain and inflammation.
Possible side effects of celecoxib include an increased risk for thrombosis (blood clot), which can lead to a heart attack or stroke. Celecoxib also carries a risk for GI bleeding and the development of a rash.
It's important to note that celecoxib is contraindicated if your patient has an allergy to aspirin, NSAIDs, or sulfonamides (e.g., sulfasalazine). Do not administer celecoxib to patients with these allergies.
Salicylate - Aspirin (Bayer)
Aspirin is a salicylate (salt or ester of salicylic acid) which is used to treat pain, inflammation, and fever. Aspirin can be used to prevent a heart attack in patients who are at risk. In your nursing career, you will encounter many patients who get a baby aspirin every day to help prevent a myocardial infarction.
Aspirin can also be used to treat Kawasaki disease, which is a systemic inflammation of blood vessels that can affect children. Kawasaki disease is covered in our Pediatric Nursing Flashcards.
Mode of action
The mode of action of aspirin is to inhibit prostaglandin synthesis and to decrease platelet aggregation.
Platelet aggregation is how blood clots form. During a heart attack, blood clots form in a narrowed artery and block the flow of blood to the heart. By keeping platelets from aggregating, aspirin can help prevent blood clots from forming, thus helping to prevent heart attacks.
It's important to remember the side effects of aspirin. Side effects of aspirin include GI upset, GI bleeding, as well as a rash. Similar to NSAIDs, if your patient has a peptic ulcer disease or some kind of bleeding disorder, then aspirin is contraindicated and should not be given to them.
Why shouldn't aspirin be given to children?
Do not administer aspirin to children with a fever due to the risk of Reye's syndrome, which is a pediatric illness characterized by non-inflammatory encephalopathy (brain disease) and fatty changes in the liver. Reye's syndrome can be fatal. This disorder is also covered in our Pediatric Nursing Flashcards.
When you have a patient taking aspirin, it's important to monitor them for signs of salicylism, which include tinnitus, nausea and vomiting, and respiratory alkalosis.
Check out our Arterial Blood Gas (ABG) Interpretation flashcards to learn how to identify respiratory alkalosis.
Aspirin side effects = ASPIRIN.
- Abdominal pain
- Peptic ulcer disease
- Intestinal blood loss
- Reye's syndrome
- Itchy rash
- Noise (tinnitus)
Okay. We are still working through our nervous system medications. We will now be talking about analgesics. If you are following along with our flashcards, we are on flashcard number 69. So in this video, we will talk about antipyretics, NSAIDs, and salicylates.
Alright. Let's first talk about an antipyretic medication, which is acetaminophen or Tylenol is the brand name.
Acetaminophen is used for mild to moderate pain and for a fever.
It works by inhibiting prostaglandin synthesis in the CNS.
It doesn't have many side effects, but the one important side effect that it does have is hepatotoxicity with large doses.
So it actually carries a black-box warning because of this risk for hepatotoxicity. So it's going to be really important that your patient not exceed 4 grams a day of acetaminophen.
And keep in mind that many over-the-counter products, like for colds, do contain acetaminophen as well. So if your patient is using acetaminophen for pain and also using a cold product with acetaminophen, they can get too much of that. They may exceed that 4 grams a day. So definitely keep an eye on that and provide that education to your patient.
And also keep in mind that acetylcysteine is the antidote for an acetaminophen overdose.
Alright. Now, let's talk about NSAIDs, which are non-steroidal anti-inflammatory drugs. Medications that fall within this class include ibuprofen, naproxen, ketorolac, as well as indomethacin.
You would use an NSAID for mild to moderate pain, fever, or inflammation. So you'll notice when we talked about acetaminophen, we didn't include inflammation because it really doesn't work that well for that purpose. But NSAIDs can help decrease inflammation.
In addition, indomethacin can help close a patent ductus arteriosus, or PDA, in premature babies.
In terms of the mode of action, NSAIDs work to inhibit prostaglandin synthesis.
Side effects are definitely more numerous than what we saw with acetaminophen. So side effects can include GI upset, GI bleeding, renal toxicity, a rash, and possible headache.
So some important teaching-- if your patient has peptic ulcer disease or any other kind of bleeding disorder, then NSAIDs would really be contraindicated because of that risk of GI bleeding. In addition, you should counsel your patient to avoid alcohol, as this can also increase the risk for a GI bleed when using NSAIDs.
Alright. Let's talk about another NSAID that is a COX-2 inhibitor. The medication that falls within this class is celecoxib or brand name Celebrex.
This medication can be used for osteoarthritis as well as rheumatoid arthritis. It works by inhibiting the COX-2 enzyme which decreases prostaglandin synthesis, and that in turn causes a decrease in pain and inflammation.
So my little tip for remembering this medication is that, "with celecoxib you can celebrate, since you don't have any more arthritis pain."
Possible side effects include an increased risk for thrombosis, which can lead to an MI or stroke. It also carries a risk for GI bleeding and the development of a rash.
So it's important to note that celecoxib would be contraindicated if your patient has an allergy to aspirin, NSAIDs, or sulfonamides.
Now let's talk about a salicylate, which is aspirin.
So aspirin is used to treat pain, inflammation, fever, it can also be used to treat Kawasaki disease and it could be used to prevent an MI in patients who are at risk.
So there's plenty of patients out there that get a little baby aspirin every day to help prevent a myocardial infarction.
The mode of action of aspirin is to inhibit prostaglandin synthesis. It also decreases platelet aggregation.
Side effects for aspirin are important to know. They include tinnitus which is ringing in the ear, GI upset, GI bleeding, as well as a rash. So if your patient has peptic ulcer disease or some kind of bleeding disorder, then you would not want to give aspirin to them. Also, you would not give aspirin to children with a fever due to the risk for Reye's syndrome.
And then, it's important to monitor your patient for signs of salicylism which include tinnitus, nausea and vomiting, and respiratory alkalosis.
So the Cool Chicken hint that's at the top of this card uses the word aspirin to help you remember some of the key side effects.
So in the word aspirin, A stands for abdominal pain or GI upset which we talked about.
S stands for salicylism which is a key thing we're going to be looking for in a patient who is taking aspirin.
P stands for peptic ulcer disease.
I stands for intestinal blood loss. So that's our GI bleed.
R stands for Reye's syndrome which is something we want to avoid, which is why we're not giving it to children.
And then, I stands for itchy rash.
And then, N stands for noise. In this case, tinnitus, which is that ringing in the ears.
So hopefully, that will help you remember some of the key side effects with aspirin.
So in my next video, we will go over some more important analgesics. Thanks so much for watching and hang in there with me!
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