Antiemetics: Nursing pharmacology

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Introduction0:00–0:21

Antiemetics are a group of medications that are used to treat nausea and vomiting. These include ondansetron, metoclopramide, aprepitant, prochlorperazine, and promethazine, as well as antihistamines like diphenhydramine, and cannabinoids, such as dronabinol.Let’s start with ondansetron, which can be administered orally, intravenously, and intramuscularly.

Mechanism of action0:21–3:03

Once administered, ondansetron acts as a 5-HT3 receptor antagonist peripherally by decreasing vagal nerve stimulation, but it is also a very powerful central acting antiemetic blocking an area in the brain called chemoreceptor trigger zone, or CTZ for short.
Ondansetron is primarily used to control nausea and vomiting after surgical anesthesia, as well in individuals undergoing chemotherapy or radiotherapy.
Next, metoclopramide can be administered orally, intranasally, intravenously, and intramuscularly, and subcutaneously. Once administered, it acts by blocking dopamine receptors in the CTZ.
As a result, the levels of dopamine decrease, preventing nausea and vomiting after surgical anesthesia as well as chemotherapy-induced nausea and vomiting.
Okay, another antiemetic is aprepitant, which can be given orally, as well as intravenously in the form of fosaprepitant.
Once administered, it acts as a neurokinin receptor antagonist that blocks neurokinin-1, or NK-1, receptors in the CTZ, and thus, it can be used to prevent chemotherapy-induced nausea and vomiting.
Alright, moving onto prochlorperazine, which is a phenothiazine, and can be given orally, rectally, intravenously, and intramuscularly.
Phenothiazines block dopamine receptors in the CNS and they’re mostly used as antipsychotics. However, most phenothiazines also have antiemetic effects, and in fact, prochlorperazine is used solely as an antiemetic.
The mechanism of the antiemetic effects is complex. They’re primarily due to the blockage of D2 receptors in the CTZ, as well as due to anticholinergic and antihistamine effects.
Prochlorperazine is mainly used to treat nausea and vomiting associated with motion sickness. Okay, now antihistamines, or H1 antagonists, like diphenhydramine can be given orally, intravenously, and intramuscularly.
These medications are primarily used to treat allergic reactions, but diphenhydramine is unique in that it can also be used to treat motion sickness.
Finally, there’s dronabinol, which is the pharmaceutical form of cannabinoid that can be administered orally. Dronabinol activates cannabinoid receptors in the brain, which seems to cause appetite stimulation and antiemetic effects, and can be used to treat clients who experience chemotherapy-induced nausea and vomiting.Alright, now moving onto side effects.

Side effects3:03–5:52

Ondansetron can cause headaches, gastrointestinal disturbances like constipation, and can prolong the QT interval, leading to arrhythmias.
A life-threatening side effect of ondansetron is serotonin syndrome, which is caused by serotonin accumulation that results in overstimulation of the nervous system.
This syndrome is characterized by skin flushing, muscle rigidity, hyperthermia, agitation, seizure, and coma. It can occur in clients treated with a combination of ondansetron and other medications that increase serotonin level, such as antidepressants.
Okay, now metoclopramide can cause CNS toxicity. In females, it can lead to hyperprolactinemia, which can present with galactorrhea, which is the increase in milk production, and anovulatory amenorrhea, which is the absence of ovulation and menses.
On the other hand, in males, metoclopramide can cause gynecomastia and erectile dysfunction. Decreasing the effects of dopamine can also lead to the development of extrapyramidal symptoms within the first few days of treatment, such as acute dystonia and pseudoparkinsonism.
Now, metoclopramide can also cause restlessness, fatigue, drowsiness, and depression. Finally, metoclopramide can cause gastrointestinal disturbances, such as abdominal cramps and diarrhea.Similarly, prochlorperazine can decrease dopamine effects, leading to hyperprolactinemia and parkinsonism.
In addition, it can result in anticholinergic side effects, such as dry mouth, blurred vision, tachycardia, urinary retention, and constipation.
Finally, prochlorperazine can also cause extrapyramidal symptoms, and may have antihistamine effects, which can lead to sedation.
On the other hand, aprepitant may cause side effects like headaches, dizziness, fatigue, and hiccups! Other common side effects may include anorexia, nausea, vomiting, heartburn, and constipation.
Finally, less common but still important side effects of aprepitant include hair loss and a skin rash, as well as blood disorders like neutropenia.Moving onto antihistamines, their side effects can be subdivided into antihistaminic effects, such as sedation, increased appetite, and weight gain; anticholinergic side effects, such as dry mouth, blurred vision, tachycardia, urinary retention, and constipation; and anti-α-adrenergic effects, like orthostatic hypotension and dizziness.
Finally, dronabinol can cause side effects from cannabinoids. These include drowsiness, dizziness, confusion, delusions, anxiety, and euphoria.
In addition, dronabinol can also increase appetite and cause gastrointestinal disturbances, such as abdominal pain.As far as contraindications go, ondansetron should be avoided in clients with risk factors for QT prolongation or in combination with other medications that increase serotonin levels, and should be used with caution in clients with electrolyte abnormalities.

Contraindications & cautions5:52–6:43

On the other hand, metoclopramide is contraindicated in clients with Parkinson’s disease, as well as in those with mechanical bowel obstruction or perforation.
Additionally, as a boxed warning, metoclopramide should not be used for more than 12 weeks, as it may cause tardive dyskinesia, which can be irreversible.
Aprepitant should be used with caution in clients with severe hepatic disease, as well as those who also take warfarin. Finally, prochlorperazine has a boxed warning, contraindicating it for elderly clients with dementia-related psychosis.
Alright, if your client is prescribed an antiemetic, first review your client’s history for conditions that can cause vomiting, such as recent travel, contact with sick individuals, as well as gastrointestinal disorders or food allergies.

Nursing considerations & Client education6:43–11:44

Be sure to check your client’s current medications, noting those that can cause vomiting, such as antibiotics, opioids or NSAIDs; and confirm they are not currently taking a medication that increases serotonin levels, which could increase the risk for serotonin syndrome when combined with an antiemetic.
Then, check their medical history for conditions like QT prolongation; and note recent laboratory results, including CBC, electrolytes and liver and renal function tests.Next, assess your client’s vital signs, noting signs of dehydration, such as hypotension and tachycardia, and perform an abdominal assessment to check for any localized tenderness, distention, or altered bowel sounds.
Ask them about the onset, duration and frequency of their vomiting, as well as the amount of fluid they are able to consume, and how much urine they produce.
Then, ask about the characteristics of their vomit, and determine if it is bloody, bilious, or projectile. Also, be sure to ask about any associated symptoms, such as diarrhea, abdominal pain, lightheadedness or fever.
Be sure to teach them how to cleanse their face with a cool washcloth and perform mouth care between episodes of vomiting to increase comfort.
Encourage them to drink clear liquids as tolerated, and explain that sipping small amounts of fluid every 15 to 20 minutes is usually better tolerated than drinking large amounts of liquids less often.
As their symptoms begin to decrease, let them know that they could try eating foods that contain a lot of liquid in them, such as gelatin or popsicles.
Later, instruct them to try eating foods that can help settle their stomach, such as crackers or dry toast. Be sure to explain how the prescribed medication works to alleviate their vomiting and prevent complications, such as dehydration, electrolyte imbalances and nutritional deficits.Then, describe common side effects they may experience while taking an antiemetic, such as drowsiness, and caution your client against consuming alcohol and other medications that depress the CNS while taking an antiemetic; also advise them to avoid activities that require alertness, such as driving, until they know how the medication affects them.
If they experience dizziness, explain how changing positions slowly can help avoid injury from falls. And if they experience anticholinergic side effects like dry mouth, suggest they use sugar-free chewing gum or lozenges or take frequent sips of water.
Additional side effects like constipation and urinary retention can be managed by increasing fluids as tolerated and encouraging them to empty their bladder regularly.
Finally, teach your client to contact their healthcare provider if their symptoms become worse or they experience symptoms like palpitations; symptoms of parkinsonism like restlessness; or symptoms of tardive dyskinesia, such as abnormal movements of their facial muscles, mouth, tongue or limbs.Now, if your client is prescribed ondansetron, let your client know they can take the medication with or without food.
When a disintegrating tablet or oral soluble film is prescribed, instruct them to allow the medication to dissolve on their tongue without chewing or swallowing whole.
Also remind them to keep unused medication from dissolving by protecting them from moisture. When caring for a client receiving chemotherapy or radiation therapy, administer oral ondansetron 30 minutes before chemotherapy or 1 to 2 hours before radiation.
If you are administering oral ondansetron to prevent postoperative nausea and vomiting, be sure to administer the medication 30 to 60 minutes before induction of anesthesia.
Explain how the medication will increase their comfort after surgery and prevent complications, such as wound dehiscence and dehydration.
Also be sure to demonstrate how the client can splint their incision site should vomiting occur. When promethazine is prescribed, remember to ensure proper intravenous catheter placement into a large vein to decrease the risk of extravasation and tissue injury.
Instruct the client to let you know immediately if they feel any pain or burning sensation during administration. If extravasation is suspected, stop the infusion immediately and institute extravasation management measures, such as gentle aspiration of extravasated fluid, limb elevation and application of either warm or cold compresses, as ordered.Finally, after administering an antiemetic, monitor your client for side effects of the medication and evaluate for desired outcomes such as reduced nausea and vomiting, balanced hydration and electrolytes, adequate nutritional intake as well as increased comfort.Alright, as a quick recap….
Antiemetic medications are used to treat nausea and vomiting by blocking receptors in the chemoreceptor trigger zone. They can cause a variety of adverse effects, such as drowsiness, dry mouth, constipation, hypotension and headache, as well as cardiac arrhythmias and extrapyramidal symptoms like pseudoparkinsonism and tardive dyskinesia.

Review11:44–12:44

Nursing considerations are focused assessment of symptoms, as well as the presence of conditions or medications that can cause vomiting or increase the risk of serious side effects like serotonin syndrome.
Additional considerations include monitoring for potential side effects such as anticholinergic and extrapyramidal effects; and monitoring for the desired therapeutic outcomes of medication administration.
Finally, client teaching is focused on safe self-administration and client self-care for maintaining an adequate intake of fluids and nutrients.
for potential side effects such as anticholinergic, an extra pyramidal effects and monitoring for the desired therapeutic outcomes of medication administration.
Finally client teaching is focused on safe. Selfie, ministration and client.
Self care for maintaining an adequate intake
Antiemetics: Video, Causes, and Symptoms | Osmosis