Drugs for disorders of the bowel Flashcards
Define Nausea
Nausea is an unpleasant sensation, which may be a precursor to the forceful expulsion of gastric contents
(vomiting/emesis)
Name the parts of central nervous system that is involved in nausea and vomiting
Cortex
Thalamus
Hypothalamus
Meninges
Name the receptors of th vestibular system that are involves in Nausea and vomiting
H1 receptor
M1 receptor
Name the receptors for GIT and heart that are involved in nausea and vomiting
Mechanoreceptors
Chemoreceptors
5-HT3 receptors
Name the receptors in the vomiting center (nucleus of tractu solitarius) that are involved in nausea and vomiting
H1
M1
NK1
5-HT1
Name the receptors in the chemoreceptor trigger zone that are involved in nausea and vomiting
Chemoreceptor
D2
NK1
5-HT3
Explain the pathophysiology of emesis in vomiting center
Vomiting centre:
* The physical act of vomiting is co-ordinated centrally by the vomiting (or emetic) centre in the medulla
* Protected by blood-brain-barrier(BBB)- lipophilic drugs
* The vomiting centre is very rich in muscarinic (M1) receptors (ACH NT) and histamine (H1) receptors (histamine is the NT)
Explain the nertwork of neural pathways that intergrate signals arriving directly from other locations
network of neural pathways that integrate signals arriving directly from other
locations such as:
* Visceral impulses from the GIT, bile ducts, genito-urinary tract.
* Labyrinth in the inner ear through the vestibular nuclei (which explains the mechanism of motion and Meniere’s disease)
* It receives input from higher cortical centres, explaining why unpleasant or repulsive sights
or smells, or strong emotional stimuli, can sometimes induce nausea and vomiting. (emotional, visual, olfactory impulses)
Explain the pathophysiology of emesis in the chemoreceptor trigger zone
Chemoreceptor trigger zone (CTZ)
* The CTZ is found in the area postrema in the medulla,
* Not protected by BBB-hydrophilic drugs
* It has receptors that are stimulated by chemical substances, toxins and emetogenic drugs eg cytotoxic drugs, opioids
* It is rich in D2, 5HT and neurokinin receptors. The neurotransmitters at these receptors are dopamine, serotonin and subst P respectively.
* Opioid receptors are also found in the CTZ (why opioids cause N/V)
* Emetogenic drugs cause vomiting by stimulating the receptors
Explain the relavance for the presence of nausea and vomoting in the presence of abdominal pain
N&V as a symptom of appendicitis, cholecystitis (inflammation of gallbladder) & cholelithiasis
(presence of formation of gallstones) – abdominal pain would be the presenting symptom
Explain the timing of nausea and vomiting
Early morning vomiting = ?Pregnancy / excess alcohol intake
Immediately after food = ?gastritis
1 or more hours after food = ?peptic ulcers
List the signs of infection for nausea and vomiting
Acute gastroenteritis (AGE) with other symptoms = diarrhoea, fever, abdominal
discomfort
? Food contamination = ask if others also affected
List the conditions where nausea and vomiting to eliminate
- N&V associated with headaches (migraines / raised intracranial
pressure) - N&V in neonates (birth to 1 month) = ALWAYS referred
- N&V (differentiate from regurgitation) in infants (1 – 12 months) -
refer in 24 hours - N&V in children – rehydration!
- Medicine-induced
- Middle ear diseases
List the antiemetics drug classes available in SA
Neurokinin-1 receptor antagonists
Antihistamines & Antimuscarinics
(anticholinergics
Dopamine antagonists
Propulsives (D2 antagonists)
Serotonin (5HT3) antagonists
List the examples for neurokinin-1 receptor antagonist
Aprepitant/fosaprepitant (Emend®)
