Antiemetics Flashcards
What class of drug is Metoclopramide?
Dopamine 2 receptor antagonist
metoclopramide is also involved with serotonin
5HT4 (increases peristalsis, increase smooth muscle contraction, increase gut secretion) AGONIST
5HT3 (causes N+V) ANTAGONIST
What are the common indications for Metoclopramide?
Post operative nausea, vomiting and certain digestive disorders.
What is the mechanism of action of Metoclopramide?
Central dopamine antagonist
Blocks messages from the CTZ (chemoreceptor trigger zone) and the vomiting centre
Peripheral cholinergic agonist. Increases tone and motility of the stomach and intestines, speeding up digestion (5HT4) - why it is good for GORD
why is metocloperamide known as a pro kinetic drug
- increases the tone of the LOS and causes gastric emptying and increases the gut motility
What are the adverse effects of Metoclopramide?
Depression, diarrhoea, drowsiness, hypotension and galactorrhoea
What are the drug-drug interactions of Metoclopramide?
Anti-psychotic drugs, dopamine agonists
- can give parkinsonian effects as it can cross the BBB
if a patient is on metocloperamide and is suffering from parkinsonian effects what other medication could you switch them too?
Domperidone
It does not cross the BBB and is metabolised peripherally
How can you remember Metoclopramide?
What class of drug is Ondansetron?
Serotonin antagonist
5Ht3 receptor antagonist
What are the common indications of Ondansetron?
To prevent nausea and vomiting in chemotherapy
What is the mechanism of action of Ondansetron?
Blocks (vagal) afferent signals from the gut to the CTZ
Peripherally reduces GI motility and reduces GI secretions
What are the adverse effects of Ondansetron?
Constipation, headache, elevated liver enzymes
Extra-pyramidal effects- dystonia, parkinsonism
What are the warnings with Ondansetron?
Subacute abdominal obstruction, susceptible to long QT
What are the drug-drug interactions of Ondansetron?
Serotonin agonists, drugs that prolong the QT interval (Tramadol)
How can you remember Ondansetron?
what class is hyoscine hydrobromide
muscarinic receptor blocker at the vestibular nuclei
blocks acetylcholine
how does hyoscine hydrobromide work
competitive blockade of the myscarinic acetylcholine receptors in the CTZ
what are some side effects of hyoscine hydrobromide
glaucoma and dry mouth as it blocks the muscarinic receptors
what is a condition in which you shouldn’t prescribe hyoscine hydrobromide
myasthenia graves as it blocks the muscarinic receptors
what class of drug is ranitidine
Anti histamine (H2)
how does Ranitidine work
It is a competitive reversible inhibitor of histamine in the gastric parietal cells
= stops the gastric acid secretion and reduces H conc
when would you prescribe ranitidine
when someone has high stomach acid
what class of drug is cyclizine
H1 receptor blocker
how does cyclizine work
acts at the vestibular nuclei and inhibits histaminergic signals from vestibular system to CTZ
What are some uses of cyclizine
motion sickness
what is promethazine used for
morning sickness
what is the first line medication for bowel obstruction
cyclizine then give dexamethasone
what are two anti-emetic drugs that can be given to pregnant women who are feeling morning sickness
promethazine and prochlorperazine
what class of drug is haloperidol
D2 receptor antagonist
how does haloperidol work
acts on the CTZ
causes the LOS to close
increases gastric contraction
and reduces the pylorus tone so it opens
haloperidol is an anti-emetic but it can also be classed into what other drug type
anti-psychotic
can be used to treat schizophrenia
what is an ADR of haloperidol
it is a D2 antagonist so can cause prolonged QT
DO NOT give to someone who has Parkinson’s
what are some side effects of haloperidol
sedation
hypotension
Chlorpromazine and levomepromazine are both from which drug class
D2 receptor antagonist
Dexamethasone is what class of drug
corticosteroid
when is dexamethasone used
in chemo when people feel Sick and nauseous
GIVE ondansetron too of not strong enough
what is a side effect of dexamethasone
HIGH SUGAR
all steroids increase sugar levels
increased weight
Aprepitant and fosaprepitant are class of what drug
neurokinin-1 receptor antagonist
how does Aprepitant work
prevents the action of substance P at CTZ and peripheral nerves
boosts the effect of the 5HT3 receptor antagonist
what other drug class can aprepitant be in
- anti anxiety
anti-psychotic
