GIT Disorders and Motility Dysfunction

Question 1

Vestibular system receptor

Answer 1

H1R

M1R

Question 2

CTZ receptor

Answer 2

D2R

NK1R

5HT3R

Question 3

Vomiting center receptors

Answer 3

H1R

M1R

Nk1R

5HT3R

Question 4

H₁ Receptor Antagonists

Answer 4

1. Cylicine: motion sickness, vertigo, vestibular disorders
2. Cinnarizine: motion sickness, vertigo, vestibular disorders
3. Promethazine: severe motion sickness of pregnancy

Question 5

H₁ Receptor antagonist pharmacokinetics

Answer 5

• Peak at about 4 hrs post ingestion
• Adverse effects:
  
  • drowsiness
  • dry mouth
  • blurred vision

Question 6

Muscarinic receptor antagonists

Answer 6

1. Hyoscine
2. Scopolamine

• ​general use
• may be used for prophylaxis
• Adverse effects:​
  
  • ​Dry mouth
  • Blurred vision
  • LESS SEDATION THAN ANTIHISTAMINES

Question 7

5HT₃ receptor antagonists

Answer 7

Ondansetron

• directly blocks the receptor in the CTZ
• Uses:
  
  • _​_Postoperative nausea in conjunction with cytotoxiuc (anticancer) drugs
• Adverse effects: relatively uncommon
  
  • ​Headaches
  • GI upset

Question 8

D₂ Receptor Antagonist

Answer 8

1. Metoclopramide
   
   • ​​acts centrally in CTZ
   • acts on gi as well
   • Side effect:
     
     • _​_due to blocking dopamine receptors in cns
2. Domperidone
   
   • ​​does not penetrate cns
     
     • less central side effects

Question 9

Cannabinoids

Answer 9

Nabilone

• synthetic cannabinoid
• chemotherapy asssoicacted NV
• helps increase apetite

Question 10

NK1R antagonist

Answer 10

NK1R:

• Substance P and its receptor are in the vomiting center
• Activation leads to vomiting

Aprepitant:

• antagonist
• used in chemotherapy induced NV

Question 11

Purgatives

Answer 11

• accelerate passage of food
• make sure no obstruction

Question 12

Bulk Laxative

Answer 12

Methylcellulose and Bran

• increases volume of non absrobable solid residue
• Pollysacc polymer not digested
• forms a bulky hydrated mass in lumen that promotes peristalsis and improves decal consistency
• takes several days to work
• NO serious side effects

Question 13

Osmotic laxative

Answer 13

lactulose, Mgsulfate

• retaining fluid in bowel by osmosis
• accelerates transfer of gut contents thru small intestine
  
  • large amount enters colon
  • distended colon causes purgation

Question 14

Stimulant Purgatives

Answer 14

Senna, Bisacodyl

• stimulates colonic activity
• increases peristalsis
  
  • stimulates enteric nerves
• 1 dose of senna produces action within 8 hours
• Bisacodyl can be given orally or as a suppository
  
  • stimulates rectal mucosa causing peristaltic action that causes defecation in 15-30 minutes

Question 15

Overuse of laxatives

Answer 15

dependency due to atonic colon

Question 16

Diarrhea

Answer 16

• liquid stool
• Increase in gi motility and increased secretion (decreased absorption) of fluid
• loss of H20 and electrolytes

Question 17

Treating diarrhea

Answer 17

1. Maintain fluid and electrolyte balance
   
   • ORT
2. ANti-infectice agents
   
   • only sevre cases may require antibacterial therapy
   • mostly self limiting and viral
3. Anti-diarrheal drugs
   
   • modifies fluid and electrolyte transport

Question 18

MAintaining fluid electrolyte balance

Answer 18

ORT

• Not reduce diarrhea
• corrects the imbalance
• body eliminates pathogens
• NaCl, KCl, NaCitrate, Cl, Glucose

Question 19

Anti-DIarrhea

Answer 19

Opiates: Loperamide, Diphenoxylate, Codeine

• loperamide poorly penetrates CNS
• decreased diarrhea with less cns se
• acts on µ opioid receptor in GIT
  
  • relatively selective
  • decreases motility and increases transit time which allows reabsorption of water
  • causes constipation and drowsiness

Question 20

Adsorbents

Answer 20

Kaolin, pectin, Mg Al Silicate

• adsorbing microorg or toxins by coating and protecting intestinal mucosa
• Kaolin
  
  • bulking actionn ie improved stool consistency