Drugs for disorders of the bowel 2

Question 1

D2 receptor antagonists is not indicated for what?

Answer 1

Vomiting because of motion sickness/labyrinth disturbances

Question 2

Which drugs that are prefered because they will not cross what?

Answer 2

Hydrophilic drugs prefered because will not cross BBB

Question 3

D2 receptor antagonists will block what?

Answer 3

Will not block extrapyramidal D2 receptors: dyskinesia and restlessness

Question 4

Dopamine inhibits what?

Answer 4

Dopamine inhibits prolactin, its blockage may cause breast tenderness, galactorrhoea, amenorrhea

Question 5

List 2 drugs that are D2 receptor antagonists that cross BBB

Answer 5

1. Metoclopramide
2. Prochlorperazine

Question 6

Explain the usage of Metoclopramide

Answer 6

Metoclopramide (EML): radiation therapy, postoperative vomiting, drug related N/V. Empties the stomach, relaxes the pylorus

Question 7

Adverse effects of Metoclopramide

Answer 7

AE: extrapyramidal symptoms,
slight sedation, constipation

Question 8

Explain the usage of prochloperazine

Answer 8

Prochlorperazine : radiation therapy, oncotherapy, avail as suppositories.

Question 9

Adverse effects for Prochloperazine

Answer 9

AE: jaundice

Question 10

List the drug that does not cross the BBB under D2 receptor antagonists

Answer 10

Do not cross BBB
* Domperidone: Similar to metoclopramide without crossing BBB

Question 11

The histamine and muscurinic receptor antagonist is used for what?

Answer 11

Used for all types of vomiting esp motion sickness, nausea from labyrinth disturbances

Question 12

The histamine and muscuranic receptor antagonists crosses BBB and go to which centeres

Answer 12

Cross BBB = vomiting centre & chemoreceptor trigger zone (CTZ)
Anticholinergic side-effects

Question 13

Promethazine is used for what?

Answer 13

Promethazine – sedative anithistamine – treat motion sickness & vertigo AE: Strong anticholinergic effect ,Strong sedative effect

Question 14

Cyclizine is used fr what?

Answer 14

Cyclizine – also paediatric suppositories for over 6 years – treat motion sickness

Question 15

Cinnarizine is used for what?

Answer 15

Cinnarizine - treat motion sickness, vertigo, vestibular disorders

Question 16

List 4 examples for 5-HT3 antagonists

Answer 16

Examples:
* Dolasetron
* Granisetron
* Ondansetron
* Palonosetron

Question 17

The 5-HT3 antagonists
1. Work on which zone
2. treat what?
3. Caution?

Answer 17

• Selective antagonists of 5HT receptors in chemoreceptor trigger zone (CTZ) & GIT
• N/V caused by chemotherapeutic drugs, radiation therapy
• Caution in cardiac disease- ECG abnormalities

Question 18

what is hyperemesis gravidarum

Answer 18

Severe type of vomiting during pregnancy

Question 19

When the preganant patient is hyperemesis gravidarum what to do?

Answer 19

Hyperemesis gravidarum (severe type of vomiting during pregnancy)
* Admission to hospital
* IV hydration with electrolytes and thiamine
* Parenteral antiemetics:
* IM prochlorperazine
* IV metoclopramide
* Ondansetron for pregnancies over 12 weeks if vomiting does not resolve
* Exclude organic causes: thyrotoxicosis, UTI, gestational trophoblastic disease

Question 20

LIST THE SPECIAL SITUATIONS

Answer 20

Post-operative N&V -5HT₃ antagonists (ondansetron)
Pre-operatively N&V -antimuscarinics are used to inhibit salivation and excessive respiratory
secretions during anaesthesia), 5HT₃ antagonists combined with dexamethasone
Chemotherapy-induced N&V – phenothiazides (prochlorperazine) , metoclopramide use limited by
SE.
Highly emetogenic agents (cisplatin), disrupt gastric mucosa and initiate release of 5HT from
entrochromaffin cells, which stimulate 5HT₃ receptors in afferent vagal endings and trigger the
emetic reflex – use 5HT₃ antagonists (with other drugs); cannabinoids (nabilone) used when
conventional antiemetics are not effective – recommended for hospital setting
Radiotherapy-induced N&V – 5HT₃ antagonists (e.g ondansetron).
Migraine- metoclopramide , domperidone (prokinetics)
Drug-associated N&V – phenothiazides (prochlorperazine)
Palliative care-associated N&V – use domperidome
Special situations
22

Question 21

Explain the neurokinin 1 receptor antagonists usage

Answer 21

Aprepitant
Adjunct to other antiemetics for prevention of acute or delayed N&V
due to highly emetogenic chemotherapy