30.1 Antiemetics
3 min read•june 18, 2024
Nausea and vomiting can be debilitating symptoms with various causes. Antiemetic drugs offer relief by targeting different pathways in the body that trigger these sensations. Understanding how these medications work is crucial for effective patient care.
There are several types of antiemetics, each with unique mechanisms of action. From serotonin receptor antagonists to , these drugs address nausea and vomiting in different ways. Knowing their indications, side effects, and potential interactions helps healthcare providers choose the best option for each patient.
Antiemetic Drugs
Main types and mechanisms of action
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- Serotonin (5-HT3) receptor antagonists block serotonin receptors in the gut and brain, reducing stimulation of the (, , dolasetron, )
- Dopamine receptor antagonists block dopamine receptors in the , reducing stimulation of the vomiting center (, , , droperidol)
- Antihistamines (H1 receptor antagonists) block histamine receptors in the vestibular system and vomiting center, reducing and vertigo-induced nausea and vomiting (, , diphenhydramine)
- Anticholinergics block acetylcholine receptors in the vestibular system and vomiting center, reducing motion sickness and vertigo-induced nausea and vomiting ()
- Neurokinin-1 (NK1) receptor antagonists block receptors in the gut and brain, reducing stimulation of the vomiting center ()
- Cannabinoids activate cannabinoid receptors in the brain, reducing stimulation of the vomiting center (, )
Indications, side effects, and drug interactions
- Serotonin (5-HT3) receptor antagonists
- Indications: (CINV), (PONV), radiation-induced nausea and vomiting (RINV)
- Side effects: headache, constipation, dizziness, fatigue,
- Drug interactions: increased risk of serotonin syndrome with apomorphine, tramadol, and serotonergic drugs
- Dopamine receptor antagonists
- Indications: , PONV, migraine-associated nausea and vomiting
- Side effects: (EPS), hyperprolactinemia, sedation, QT prolongation
- Drug interactions: decreased effectiveness with dopaminergic drugs, increased risk of side effects with anticholinergic drugs
- Antihistamines (H1 receptor antagonists)
- Indications: motion sickness, vertigo,
- Side effects: sedation, dry mouth, blurred vision, urinary retention
- Drug interactions: increased sedation with CNS depressants, increased risk of side effects with anticholinergic drugs
- Anticholinergics
- Indications: motion sickness, vertigo, PONV
- Side effects: dry mouth, blurred vision, urinary retention, confusion (especially in the elderly)
- Drug interactions: increased risk of side effects with other anticholinergic drugs
- Neurokinin-1 (NK1) receptor antagonists
- Indications: CINV (used in combination with 5-HT3 antagonists and corticosteroids)
- Side effects: fatigue, diarrhea, hiccups, constipation
- Drug interactions: increased aprepitant levels with CYP3A4 inhibitors, decreased aprepitant levels with CYP3A4 inducers
- Cannabinoids
- Indications: CINV, appetite stimulation in AIDS and cancer patients
- Side effects: dizziness, euphoria, dysphoria, sedation, dry mouth, tachycardia
- Drug interactions: increased sedation with CNS depressants, altered metabolism of CYP2C9 and CYP3A4 substrates
Nursing considerations
- Assess severity and cause of nausea and vomiting to guide medication selection
- Monitor vital signs, especially in patients with cardiovascular disease or electrolyte imbalances
- Assess for dehydration and provide fluid and electrolyte replacement as needed
- Administer medications as prescribed, considering route, dose, and frequency
- Monitor for side effects and adverse reactions, particularly EPS, sedation, and anticholinergic effects
- Adjust dosages or switch to alternative antiemetics if current therapy is ineffective or causing significant side effects
- Implement non-pharmacological interventions (acupressure, relaxation techniques, dietary modifications) to complement antiemetic therapy
- Collaborate with healthcare team to optimize patient's antiemetic regimen and overall care plan
Patient education
- Inform patients about purpose, expected benefits, and potential side effects of prescribed antiemetic medication(s)
- Instruct patients on how to take medication(s) correctly (dose, frequency, specific administration instructions)
- Advise patients to report severe or persistent side effects to healthcare provider
- Encourage patients to maintain adequate hydration and nutrition, even with reduced appetite
- Educate patients on non-pharmacological strategies to manage nausea and vomiting (small, frequent meals; avoiding strong odors; relaxation techniques)
- Advise patients to avoid alcohol and inform healthcare provider about other medications, supplements, or herbal products to minimize risk of drug interactions
- Instruct patients on when to seek immediate medical attention (signs of severe dehydration, uncontrolled vomiting, allergic reactions)
- Provide patients with written information or resources to reinforce verbal education and ensure comprehension
Key Terms to Review (55)
5-HT3 Receptor Antagonists: 5-HT3 receptor antagonists are a class of medications that block the action of serotonin (5-hydroxytryptamine, 5-HT) at the 5-HT3 receptor. This mechanism of action is particularly useful in the context of antiemetic therapies, as the 5-HT3 receptor is involved in the vomiting reflex.
Antiemetic Combinations: Antiemetic combinations refer to the use of two or more antiemetic medications together to manage nausea and vomiting. Antiemetics are drugs that help prevent or treat these symptoms, and combining different types can provide more effective relief for patients.
Antiemetic Prophylaxis: Antiemetic prophylaxis refers to the proactive administration of anti-nausea and anti-vomiting medications to prevent the occurrence of these symptoms, particularly in the context of medical treatments that are known to induce nausea and vomiting as side effects.
Antivert: Antivert is a brand name for meclizine, an antihistamine used to treat nausea, vomiting, and dizziness caused by motion sickness. It is also used for managing vertigo associated with vestibular system disorders.
Aprepitant: Aprepitant is an antiemetic medication used to prevent nausea and vomiting caused by chemotherapy. It works by blocking the neurokinin 1 (NK1) receptor in the brain.
Cannabinoids: Cannabinoids are chemical compounds found in cannabis that interact with the body's endocannabinoid system to produce various physiological effects. They can be used therapeutically, including as antiemetics to reduce nausea and vomiting.
Chemoreceptor Trigger Zone: The chemoreceptor trigger zone (CTZ) is a specialized area located in the medulla oblongata of the brainstem that plays a crucial role in the regulation of vomiting and nausea. It acts as a central hub, integrating various chemical and neural signals to initiate the vomiting reflex.
Chemoreceptor trigger zone (CTZ): The chemoreceptor trigger zone (CTZ) is an area in the brain that detects toxic substances in the blood and induces vomiting to expel them. It plays a significant role in the pharmacology of antiemetics.
Chemotherapy-Induced Nausea and Vomiting: Chemotherapy-induced nausea and vomiting (CINV) refers to the common side effect experienced by patients undergoing chemotherapy treatment, characterized by feelings of sickness and the involuntary expulsion of stomach contents. This term is closely linked to the topic of antiemetics, which are medications used to prevent and manage CINV.
Chlorpromazine: Chlorpromazine is an antipsychotic medication primarily used to manage schizophrenia and bipolar disorder. It is also effective as an antiemetic, particularly in preventing nausea and vomiting.
Cinvanti: Cinvanti is an antiemetic medication used to prevent nausea and vomiting caused by chemotherapy. It works by blocking neurokinin-1 (NK1) receptors in the brain.
Compazine: Compazine is a brand name for prochlorperazine, an antiemetic and antipsychotic medication used to treat nausea, vomiting, and vertigo. It belongs to the phenothiazine class of drugs.
Compro: Compro is a brand name for prochlorperazine, an antiemetic medication commonly used to treat nausea and vomiting. It works by blocking dopamine receptors in the brain.
D2 Receptors: D2 receptors are a type of dopamine receptor that are widely distributed in the brain and play a crucial role in various physiological processes, including motor control, cognition, and reward processing. These receptors are particularly relevant in the context of antiemetic medications, which target them to alleviate nausea and vomiting.
Dimenhydrinate: Dimenhydrinate is an antiemetic medication primarily used to prevent and treat nausea and vomiting. It is a derivative of diphenhydramine, an antihistamine, and is commonly used to manage motion sickness, vertigo, and other conditions that can cause these symptoms.
Dopamine Antagonism: Dopamine antagonism refers to the mechanism of action of certain medications that block or inhibit the effects of the neurotransmitter dopamine in the body. This is a key concept in the context of antiemetic medications, as dopamine antagonism is a primary way these drugs exert their anti-nausea and anti-vomiting effects.
Dronabinol: Dronabinol is a synthetic form of THC used to treat nausea and vomiting caused by chemotherapy, as well as appetite loss in AIDS patients. It works by interacting with the brain's cannabinoid receptors.
Emend: Emend is a brand name for aprepitant, a medication used to prevent nausea and vomiting caused by chemotherapy and surgery. It works by blocking neurokinin-1 (NK1) receptors in the brain.
Extrapyramidal symptoms: Extrapyramidal symptoms (EPS) are drug-induced movement disorders that include various involuntary muscle movements, typically caused by antipsychotic and antiemetic medications. Symptoms can range from mild tremors to severe motor dysfunction.
Extrapyramidal Symptoms: Extrapyramidal symptoms (EPS) are a set of movement disorders that can occur as side effects of certain medications, particularly antipsychotics and antiemetics. These symptoms involve the disruption of the normal functioning of the extrapyramidal system, which is responsible for controlling involuntary muscle movements and coordination.
Fosaprepitant: Fosaprepitant is a prodrug of aprepitant, a highly selective neurokinin-1 (NK1) receptor antagonist used as an antiemetic medication to prevent and treat nausea and vomiting associated with chemotherapy and other medical treatments.
Gastroparesis: Gastroparesis is a condition in which the stomach takes too long to empty its contents, resulting in symptoms such as nausea, vomiting, bloating, and abdominal pain. It is a disorder of gastric motility, where the stomach muscles fail to function normally, leading to delayed gastric emptying.
Granisetron: Granisetron is a 5-HT3 receptor antagonist used to prevent nausea and vomiting caused by chemotherapy, radiation therapy, or surgery. It works by blocking the action of serotonin in the brain and gut.
H1 Receptors: H1 receptors are a type of histamine receptor found in various tissues throughout the body. They are the primary targets of antihistamine drugs and play a crucial role in mediating the physiological effects of histamine, particularly in the context of allergic reactions and inflammation.
Hydroxyzine: Hydroxyzine is an antihistamine used to treat anxiety and nausea, including nausea related to gastrointestinal disorders. It works by blocking histamine receptors in the brain and other parts of the body.
Hyoscine: Hyoscine, also known as scopolamine, is a tropane alkaloid that acts as an anticholinergic agent. It is primarily used as an antiemetic, a medication that prevents or treats nausea and vomiting, in the context of 30.1 Antiemetics.
Kytril: Kytril is the brand name for granisetron, an antiemetic used to prevent nausea and vomiting caused by chemotherapy, radiation therapy, and surgery. It works by blocking serotonin receptors in the brain and gastrointestinal tract.
Marinol: Marinol is a brand name for dronabinol, a synthetic form of THC used as an antiemetic. It is primarily prescribed to treat nausea and vomiting caused by chemotherapy and to stimulate appetite in patients with AIDS.
Meclizine: Meclizine is an antihistamine used to prevent and treat nausea, vomiting, and dizziness caused by motion sickness. It also helps manage symptoms of vertigo from inner ear conditions.
Medical cannabis: Medical cannabis is the use of Cannabis sativa or derivatives thereof, as a physician-recommended form of medicine or herbal therapy. It is often used to alleviate symptoms such as nausea and vomiting, particularly for patients undergoing chemotherapy.
Metoclopramide: Metoclopramide is a medication primarily used as an antiemetic, which means it helps prevent and treat nausea and vomiting. It works by blocking certain receptors in the brain and gastrointestinal tract, which helps regulate the movement and function of the digestive system.
Morning Sickness: Morning sickness is a common condition experienced by many pregnant women, characterized by nausea and vomiting that typically occurs in the morning but can persist throughout the day. It is one of the most common symptoms associated with early pregnancy and is often considered a positive sign of a healthy pregnancy.
Motion Sickness: Motion sickness is a physiological condition that occurs when there is a disconnect between the visual and vestibular systems, leading to symptoms like nausea, vomiting, and dizziness. This term is particularly relevant in the context of antihistamines, decongestants, and antiemetics, as these drug classes can be used to prevent or treat the symptoms of motion sickness.
Nabilone: Nabilone is a synthetic cannabinoid medication used as an antiemetic to treat nausea and vomiting, particularly in patients undergoing chemotherapy. It works by mimicking the effects of the naturally occurring cannabinoid compounds found in the cannabis plant.
NK1 Receptor Antagonists: NK1 receptor antagonists are a class of drugs that block the binding and activation of neurokinin-1 (NK1) receptors, which are involved in the transmission of pain signals and the regulation of nausea and vomiting. These antagonists are primarily used as antiemetic agents to prevent and treat chemotherapy-induced nausea and vomiting.
Ondansetron: Ondansetron is an antiemetic medication used to prevent nausea and vomiting caused by chemotherapy, radiation therapy, or surgery. It works by blocking serotonin receptors in the brain and gastrointestinal tract.
Palonosetron: Palonosetron is a selective 5-hydroxytryptamine3 (5-HT3) receptor antagonist used as an antiemetic medication. It is primarily employed to prevent nausea and vomiting associated with cancer chemotherapy treatments.
Pediatric clients: Pediatric clients are children and adolescents who require medical care, including pharmacological treatments. Special considerations must be made for their unique physiological and developmental needs.
Phenergan: Phenergan, also known as promethazine, is an antihistamine used to treat nausea and vomiting. It also has sedative properties which can be beneficial in the management of motion sickness and allergic reactions.
Phenothiazines: Phenothiazines are a class of antipsychotic and antiemetic drugs that block dopamine receptors in the brain and chemoreceptor trigger zone, reducing nausea and vomiting. They are commonly used to manage symptoms associated with gastrointestinal disorders and chemotherapy.
Postoperative Nausea and Vomiting: Postoperative nausea and vomiting (PONV) refers to the unpleasant sensation of feeling the need to vomit or the actual act of vomiting that can occur after a surgical procedure. It is a common side effect that can significantly impact a patient's recovery and well-being.
Prochlorperazine: Prochlorperazine is an antiemetic medication used to treat nausea and vomiting. It belongs to the phenothiazine class of drugs and works by blocking dopamine receptors in the brain.
Promethazine: Promethazine is an antihistamine and antiemetic used to prevent nausea and vomiting. It works by blocking histamine receptors in the brain, which helps control symptoms of motion sickness, allergies, and gastrointestinal disorders.
QT Prolongation: QT prolongation is an electrocardiographic (ECG) finding characterized by an abnormally long time interval between the start of the Q wave and the end of the T wave, which represents the duration of ventricular depolarization and repolarization. This condition can increase the risk of potentially life-threatening cardiac arrhythmias, such as torsades de pointes, and is an important consideration in the context of various drug therapies.
Rescue Medication: Rescue medication refers to a type of medication that is used to quickly relieve or stop an acute or sudden symptom or episode, typically in the context of a chronic or ongoing condition. It is designed to provide rapid, temporary relief when a patient's regular maintenance medication is not sufficient to control the immediate symptoms.
Rolapitant: Rolapitant is a neurokinin-1 (NK1) receptor antagonist used to prevent delayed nausea and vomiting associated with chemotherapy. It works by blocking the action of substance P/neurokinin 1 on its receptors in the brain.
Scopolamine: Scopolamine is a tropane alkaloid compound derived from plants of the nightshade family. It is known for its potent anticholinergic effects, making it a valuable medication for treating nervous system disorders and managing nausea and vomiting.
Scopolamine transdermal patch: A Scopolamine transdermal patch is a medicated adhesive patch placed on the skin to deliver scopolamine, used primarily to prevent nausea and vomiting associated with motion sickness or postoperative recovery. The drug works by blocking certain neurotransmitters in the brain that trigger these symptoms.
Serotonin Antagonism: Serotonin antagonism refers to the inhibition or blockade of serotonin (5-HT) receptors, preventing the binding and subsequent activation of these receptors by serotonin. This mechanism of action is particularly relevant in the context of antiemetic medications used to manage nausea and vomiting.
Substance P: Substance P is a neuropeptide that acts as a neurotransmitter and neuromodulator in the central and peripheral nervous systems. It is involved in the transmission of pain signals and plays a crucial role in the pathophysiology of migraine headaches and the regulation of nausea and vomiting.
Transderm-Scop: Transderm-Scop is a transdermal patch containing scopolamine, used to prevent nausea and vomiting. It is commonly applied behind the ear for motion sickness and postoperative recovery.
Varubi: Varubi (rolapitant) is a neurokinin-1 (NK1) receptor antagonist used to prevent delayed nausea and vomiting associated with chemotherapy. It works by blocking the action of substance P/neurokinin 1 in the brain.
Vistaril: Vistaril is a brand name for hydroxyzine, an antihistamine used to treat anxiety and nausea. It works by blocking histamine receptors in the brain to reduce symptoms.
Vomiting Center: The vomiting center is a group of neurons located in the medulla oblongata of the brainstem that coordinates the complex process of vomiting. It is responsible for integrating various sensory inputs and initiating the motor responses necessary for the act of vomiting.
Zofran: Zofran (ondansetron) is a serotonin 5-HT3 receptor antagonist used to prevent nausea and vomiting caused by chemotherapy, radiation therapy, and surgery. It works by blocking the action of serotonin, a natural substance that may cause nausea and vomiting.