Nausea and vomiting Flashcards
(42 cards)
Why are antiemetics generally only prescribed when the cause of vomiting is known?
Antiemetics may delay diagnosis, especially in children, when the cause of vomiting is unknown.
What are common antihistamines used as antiemetics?
Cinnarizine, cyclizine, promethazine hydrochloride, and promethazine teoclate.
What is a key side effect of antihistamines used as antiemetics?
Drowsiness and antimuscarinic effects - dry mouth, constipation, blurred vision, urinary retention, and in some cases, confusion or agitation.
What is the action of phenothiazines as antiemetics?
They are dopamine antagonists and act by blocking the chemoreceptor trigger zone in the brain.
What are some potential side effects of phenothiazines?
Severe dystonic reactions, especially in children.
What is metoclopramide’s action as an antiemetic?
It acts on the gastric smooth muscle, stimulating gastric emptying, and is effective for emesis associated with gastrointestinal and biliary disease.
Why is domperidone less likely to cause central side effects?
It does not readily cross the blood-brain barrier.
Which antiemetic drugs are used for chemotherapy-induced nausea and vomiting?
5HT3-receptor antagonists (e.g., granisetron, ondansetron, palonosetron), dexamethasone, and neurokinin 1-receptor antagonists (e.g., aprepitant, fosaprepitant).
What is the first-line antiemetic treatment for nausea and vomiting during pregnancy?
Cyclizine or promethazine (antihistamines), prochlorperazine or chlorpromazine (phenothiazines), or doxylamine/pyridoxine combination.
What should be done if first-line antiemetic treatment for pregnancy-induced nausea is ineffective?
Switch to a second-line antiemetic such as oral metoclopramide, domperidone, or ondansetron.
When is oral prednisolone used as an antiemetic in pregnancy?
As third-line treatment when second-line antiemetics are ineffective.
What condition may require regular antiemetic therapy, intravenous fluid, and nutritional support during pregnancy?
Hyperemesis gravidarum.
What is the main treatment for postoperative nausea and vomiting?
A combination of antiemetic drugs from different therapeutic classes, such as 5HT3-receptor antagonists, dexamethasone, droperidol, and haloperidol.
Which drug is licensed to prevent motion sickness?
Hyoscine hydrobromide.
What is the main treatment for acute attacks of Ménière’s disease?
Short courses of antihistamines (e.g., cinnarizine, cyclizine, promethazine teoclate) and phenothiazines (e.g., prochlorperazine).
What is the role of betahistine dihydrochloride in Ménière’s disease?
It can reduce the frequency and severity of hearing loss, tinnitus, and vertigo in recurrent attacks.
What are the common clinical indications for D2 antagonist antiemetics?
Prophylaxis and treatment of nausea and vomiting, especially due to reduced gut motility (e.g. opioids, gastroparesis).
Name two commonly used D2 receptor antagonist antiemetics.
Metoclopramide and domperidone.
Where is the chemoreceptor trigger zone (CTZ) located, and why is it important?
In the medulla, outside the blood-brain barrier; it detects emetogenic substances and is rich in D2 receptors.
What is the mechanism of action of D2 receptor antagonists in antiemesis?
Block D2 receptors in the CTZ and GI tract, reducing nausea and promoting gastric emptying (stomach contents move to the small intestine).
Which D2 antagonist is less likely to cause extrapyramidal side effects and why?
Domperidone, because it does not cross the blood–brain barrier.
What is a serious extrapyramidal side effect associated with metoclopramide?
Acute dystonic reactions, such as oculogyric crisis - a rare, acute dystonic reaction where the eyes involuntarily deviate upwards, often with other dystonic symptoms like neck or tongue movements.
What is the typical adult dose for both metoclopramide and domperidone?
10 mg up to three times daily.
When is the use of D2 antagonist antiemetics contraindicated?
In gastrointestinal obstruction or perforation due to their prokinetic action.
