N+V and antiemetics

Question 1

When does vomiting occur

Answer 1

when vomiting centre in brain activated by input from the chemoreceptor trigger zone

Question 2

When are antiemetics given

Answer 2

generally only when cause of vomiting known because otherwise they can delay diagnosis, esp in children

Question 3

how do anti emetics work

Answer 3

by blocking receptors in CTZ, chosen according to the aetiology of the vomiting

Question 4

metoclopramide - MOA

Answer 4

dopamine receptor antagonist
activity closely resembles phenothiazines
acts directly on gastric smooth muscle, simulating gastric emptying
thus may be superior to phenothiazines for emesis associated with GI and biliary disease

Question 5

which one for emesis associated with GI and biliary disease and why?

Answer 5

metoclopramide because it acts directly on gastric smooth muscle and stimulates gastric emptying

Question 6

what is the antiemetic of choice in PD and why

Answer 6

domperidone because it does not cross BBB so is less likely to cause central effects e.g. sedation and dystonic reactions
use low dose in PD to treat nausea caused by dopaminergic drugs

Question 7

MOA domperidone

Answer 7

acts at CRZ and is a dopamine antagonist that does NOT cross BBB

Question 8

phenothiazine antipsychotics how do they work

Answer 8

centrally at CTZ and are dopamine antagonists
severe dystonic reactions can sometimes occur, esp in children

Question 9

antihistamines MOA

Answer 9

e.g. cinnarizine, cyclizine, promethazine
they are dopamine antagonists
duration of action and antimuscarinic effects will differ between which one is used

Question 10

which antihistamine is the most effective in motion sickness

Answer 10

hyoscine hydrobromide

Question 11

hyoscine hydrobromide or butylbormide - which is most effective in motion sickness

Answer 11

hydrobromide

Question 12

this antiemetic closely resembles the action of phenothiazines

Answer 12

metoclopramide

Question 13

name the 3 5-HT3 receptor antagonists for chemotherapy or post op n+v

Answer 13

granisetron, ondansetron, palonosetron

Question 14

this CC has antiemetic effects and is used in the management of cancer chemo, post op, and can be used alone or in combination with other antiemetics

Answer 14

dexamethasone

Question 15

nabilone is a synthetic cannabinoid. discuss its use as an antiemetic

Answer 15

used in chemo n+v that is unresponsive to other anti emetics
consider as add on treatment for chemo induced n+v that is unresponsive to optimised conventional antiemetics

Question 16

NK1R antagonists e.g. aprepitant, fosprepitant and rolapritant are used to prevent chemo therapy associated n+v. they are usually given in combination with ….

Answer 16

dexamethasone + 5HT3 antagonist e.g. ondansetron, polonoserton, granisetron

Question 17

does metoclopramide have a pro kinetic effect (promotes movement)

Answer 17

yes. acts directly on gut to promote gastric emptying.
thus useful in gasproduodenal, hepatic and biliary disease

Question 18

restrictions to use - metoclopramide MHRA due to risk of neurological adverse effects

Answer 18

• in adults 18 and above only use for prevention of PONV, radio-therapy induced NV, delayed (but not acute) chemo induced NV, symptomatic treatment of NV, including that associated with acute migraine (where it may also be used to improve absorption of oral analgesics)
• max 5 days
• does not apply to unlicensed uses e.g. palliative care

Question 19

metoclopramide dose

Answer 19

10mg TDS
max daily dose 500mcg/kg

Question 20

CI metoclopramide

Answer 20

3–4 days after gastrointestinal surgery; epilepsy; gastro-intestinal haemorrhage; gastro-intestinal obstruction; gastro-intestinal perforation; phaeochromocytoma

Question 21

true or false - acute dystonic reactions from metoclopramide are more common in young, esp girls and young females, and the elderly

Answer 21

true

Question 22

this anti Parkinsonism drug is used to abort dystonic reactions e.g. caused by metoclopramide

Answer 22

procyclidine

Question 23

does metoclopramide interact with antipsychotics

Answer 23

yes increased extrapyramidal SE

Question 24

is domperidone pro kinetic

Answer 24

yes because it acts directly on gut to promote gastric emptying - prokinetic effect

Question 25

MHRA advice on domperidone - lack of efficacy in children and reminder of CI in adults and teens

Answer 25

• ineffective in people under 12 or under 35kg
• max duration of treatment should not usually exceed 1 week
• risk of cardiac effects e.g. arrhythmia, it prolongs QT interval

Question 26

CI for domperidone

Answer 26

Cardiac disease; conditions where cardiac conduction is, or could be, impaired; gastro-intestinal haemorrhage; gastro-intestinal mechanical obstruction; gastro-intestinal mechanical perforation; if increased gastro-intestinal motility harmful; prolactinoma

Question 27

interactions with domperidone

Answer 27

Potent CYP3A4 inhibitor e.g. amiodarone, ketoconazole, erythromycin
Drugs causing QT prolong e.g. amiodarone, SSRIs, quinolone

Question 28

Important interactions of 5HT2R antagonists (e.g. ondansetron) are to do with the following (3)

Answer 28

increased risk of serotonin syndrome
increased risk of TDP with HYPOkalaemia
increased risk of QT interval prolongations

Question 29

what are dystonic reactions/dystonia

Answer 29

Dystonia is a neurological movement disorder. People with dystonia experience involuntary muscle spasms and contractions. Movements are often repetitive and cause unusual, awkward and sometimes painful postures