Anti-Emetics Flashcards by Rachael Christie

What are some of the causes for nausea and vomiting?

Gastrointestinal irritation
Infections
Drugs
Radiotherapy / chemotherapy
Motion /travel sickness
Vertigo
Post operative
Psychological
Pregnancy
Intracranial pathology
Migraine

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What are the consequences of nausea and vomiting?

Dehydration
Malnutrition
Alkalosis / electrolyte imbalance
Aspiration of gastric contents
Wound dehiscence
Reduced drug absorption
Mood changes

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What treatments are used for severe and persistent vomiting?

Rectal suppositories
Buccal tablets

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What systems are affected by vomiting?

Oesophagus
Stomach
Upper small intestine
Respiratory system
Diaphragm

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What are the four basic steps of vomiting?

Relaxation
Contraction
Inspiration
Contraction

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What has to relax in order for you to vomit?

Oesophagus
Oesophageal & cardiac sphincters
Fundus of stomach

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What contracts during vomiting?

Duodenum
Pylorus of stomach
Diaphragm and abdominal muscles to compress the stomach
Push contents to exit via the mouth

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What is the function of vomiting?

It is a defensive response to eliminate toxic irritating material
To empty the upper small intestine and stomach

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How well understood is process vomiting?

Pathways are poorly defined
Multiple inputs and receptors involved
Key role for chemoreceptor trigger zone and vomiting centre in integration

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Where is the chemoreceptor trigger zone found?

Located within the area postrema of the 4th ventricle

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How can the chemoreceptor trigger zone detect emetic stimuli in the blood and CSF?

It lacks an effective blood brain barrier

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Where does the chemoreceptor trigger zone receive info from?

Vagal afferent input from GI tract
Vomiting centre
Higher centres involved in visual, olfactory and emotional processing

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What counts as emetic stimuli?

Bacterial toxins
Cytotoxic drugs
Mechanical distension

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What is released due to activation by emetic stimuli?

Serotonin from enterochromaffin cells in the gut

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What are enterochromaffin cells?

Neuroendocrine cells found in the gastric mucosa in the vicinity of parietal cells

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What do enterochromaffin cells do?

Aid in the production of gastric acid via histamine release

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What and where is the vomiting centre?

A collection of effector nuclei found in the medulla oblongata

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Where does the vomiting centre receive inputs from?

Gut
Chemoreceptor trigger zone
Cardiovascular system
Limbic nuclei

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What sort of information is passed on from the limbic nuclei?

Olfactory
Emotional
Hormonal
Stress
Pain
Anticipatory inputs

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What does the vomiting centre do?

Coordinates visceral and somatic components of the emetic reflex

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What are some of the treatments of nausea and vomiting?

Gastro-prokinetic agents
Sphincter modulators
5HT3 antagonists
Histamine antagonists
Muscarinic antagonists
Dopamine antagonists
Cannabinoids
Benzodiazepines

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What treatments targets the higher centres pathway of vomiting?

Benzodiazepines

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What pathway do 5HT3 antagonists target?

Stomach inputs to:
Chemoreceptor trigger zone
Vomiting centre

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What treatments target the pathway from the chemoreceptor trigger zone to the vomiting centre?

Histamine, muscarinic, dopamine antagonists
Cannabinoids

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What anti emetics are used for motion sickness and vertigo?

Muscarinic antagonists Antihistamines

Give an example of a muscarinic antagonist used for vomiting

Hyoscine

What are the side effects of muscarinic antagonists?

Variable sedative and anti muscarinic side effects: Dry mouth Blurred vision

Give two examples of anti histamines used as ant emetics

Meclozine Cinnarizine

What is the side effect associated with anti histamines?

Sedation / sedative effects

What is metocloperamide?

An anti emetic Antagonist of D2 and 5HT3 receptors Agonist of 5HT4 receptors

When is metocloperamide used?

Emesis related to hepatic/gastro-duodenal illness Migraine Chemo/ radio therapy Initial emesis due to opioid analgesia in palliative care

What does metacloperamide do?

Facilitates gastric emptying Some effects on the chemoreceptor trigger zone

What are the side effects associated with metocloperamide use?

Sedative Prolactin release (menstrual disorders) Extra pyramidal effects (D2)

Describe the extra pyramidal side effects of metocloperamide

Dystonia - dragging leg / pulling of neck / difficulty speaking Motor impairment Muscle spasms Rigidity

What receptors does promethazine target?

Antagonism of: M H D 5HT Adrenoceptors Chemoreceptor trigger zone

What is promethazine useful?

Motion sickness Pregnancy Chemotherapy induced Post operative vomiting

What are the side effects of promethazine?

Sedative Dystonic reactions

What is olanzapine?

An atypical antipsychotic Also useful as an anti emetic

What receptors does olanzapine target?

Antagonism of Dopamine 5HT Histamine Muscarinic Adrenoceptors Action on chemoreceptor trigger zone

What is olanzapine mainly used to treat?

Breakthrough chemotherapy induced nausea and vomiting (CINV)

What are side effects of using olanzapine?

Sedative Dystonic reactions Weight gain Metabolic disturbances

What receptors does doperidone interact with?

Chemoreceptor trigger zone D2/D3

When is domperidone used?

To limit emesis associated with dopamine agonists in Parkinson’s disease CINV?

Why is domperidone less efficient than metocloperamide and promethazine?

It does not cross the blood brain barrier as readily as

Is there a positive to taking domperidone?

Less sedative effects and less dystonia

What drugs block the 5HT3 receptors in the GI tract?

Ondansetron Granisetron Ramosetron Palonosetron

When are serotonin antagonists used?

Acute chemo / radio therapy induced Post operative emesis

How is the desensitisation to 5HT3 antagonists overcome?

Adding corticosteroid (dexamethasone) Mechanism unclear

What are the side effects of ondansetron, granisetron and ramosetron?

Mild headaches Constipation Increased risk of QT wave prolongation Cardiac dysrhythmias

What is palonosetron?

2nd generation 5HT3 antagonist Highly selective competitive antagonist with additional ‘allosteric’ antagonism

What does palonosetron do?

Promotes receptor internalisation Reduces receptor cross talk

What are the benefits to using palonosetron?

Increased benefit in delayed benefit following CINV & PONV Increased duration of action Does not prolong QT interval

What does dexamethasone do?

Anti inflammatory influence Reduces pain Reduces need for pro emetic opioids

What does dexamethasone act on?

Direct action on Solitary tract nucleus Interaction with Serotonin and tachykinin signalling pathways Regulation of hypothalamic pituitary adrenal axis

What are the two broad spectrum anti emetic drugs?

Aprepitant Fosaprepitant (prodrug if Aprepitant)

How do broad spectrum any emetics work?

Direct inhibition of substance P / neurokinin receptors in vomiting centre and terminal pathways

What are broad spectrum anti emetic useful for?

Vomiting caused by Peripheral / central emetic stimuli Delayed emesis of chemo Effective relief of nausea

What are the side effects of aprepitant and fosaprepitant?

Flatulence Hiccups Fatigue Drug interactions

What is an example of a combination therapy used for vomiting?

5HT3 antagonist NK1 antagonist Dexamethsone + metocloperamide for breakthrough symptoms

When are combination therapies used?

As prophylaxis in those at higher risk of CINV and PONV Effective in 70-80% of acute and delayed phases

What sort of sedatives and hypnotics are used for anticipatory anti emesis?

Barbiturates - phenobarbital Benzodiazepines - midazolam

What are risks associated with sedatives and hypnotics?

Increased risk of vomiting associated asphyxia due to a decreased level of consciousness

What is nabilone?

A synthetic derivative of Cannabinoid found in marihuana

When are Cannabinoids used?

An effective prophylaxis for CINV Possible anxiolytic properties aswell

What receptors do nabilone target?

CB1 in cerebral cortex Area postrema (chemo trigger zone) Solitary nucleus CB2 in brainstem

What are the side effects of using Cannabinoids?

Dysphoria Hallucinations Disorientation Dizziness Sedation Dry mouth

What are some of the non drug approaches that can be used in nausea and vomiting?

Ground ginger Hypnosis Fluid/ electrolyte replacement Improving nutrition Acupuncture

How does acupuncture help?

Stimulation of P6 acupoint on the wrist Useful in PONV reduced need for rescue and breakthrough therapies

Why is emesis discouraged in a patient who may have ingested a poison or corrosive?

There could be more damage done by the vomit and poison travelling back up the GI tract

Anti-Emetics Flashcards

(69 cards)