Drugs and the Gut Flashcards
Define “antagonist”
A drug or chemical which blocks the physiological response of another by binding and blocking its receptor
Define “agonist”
A drug or chemical which produces a physiological reaction by binding to its receptor
Define “irreversible binding”
An irreversible antagonist binding to a receptor which cannot be displaced
Define “side effect”
An effect which occurs additionally to the desired effect
What two places can peptic ulcers arise?
Stomach ulcer
Duodenal ulcer
State some symptoms of having ulcers
Pain in abdomen, neck, back; Bleeding; Indigestion; Heartburn; Loss of apetite; Vomiting
State two broad mechanisms of how peptic ulcers are caused
Bacterial Infection
NSAIDs
What are the names given to the three cells involved in gastric secretions?
Neck cells
Chief cells
Parietal / Oxyntic cells
What three regions of the stomach are the Neck cells found in?
Cardiac, Pylorus, Fundus
Where are Chief cells found in the stomach?
Fundus
Where are Parietal / Oxyntic cells found in the stomach?
Fundus
What kind of gastric secretion do Neck cells secrete?
Mucus
What kind of gastric secretion do Chief cells secrete?
Proteolytic enzymes
What kind of gastric secretion do Parietal / Oxyntic cells secrete?
HCl
What do the gastric glands secrete?
Gastric juice (HCl, enzymes, mucus)
To heal the peptic ulcer, we need a pH of…?
Greater than 3
Which bacteria causes Stomach ulcers?
Gram negative Heliobacter pylori
How does H. pylori cause ulcers?
H. pylori secretes urease to produce ammonia and H2C03.
What are the four types of histamine receptor, and which one is the most important for targeting treatment for ulcers?
H1, H2, H3, H4
H2 Receptor
Give three examples of H2 antagonists
Cimetidine
Ranitidine
Famotidine
State three examples of PPIs
Omeprazole
Lansoprazole
Pantoprazole
Why are PPIs very long lasting?
- Accumulation of the drug in the parietal cell canaliculi
2. Irreversible nature of proton pump inhibition
How are PPIs prodrugs?
They have a bicarbonate / enteric coat which prevents rapid exposure to stomach HCl
How can you treat H. pylori? What are the combinations?
Amoxicillin + Clarithromycin
Amoxillicin + Metronidazole
Combined therapy with PPI
Give examples of NSAID drugs which can cause Ulcers
Aspirin
Ibuprofen
Naproxen
How does NSAIDs cause ulcers?
It is a systemic drug, targeting COX-1 and COX-2 enzymes
What is often given with NSAIDs to inhibit the adverse affects of ulcer formation?
Misoprostol, which is a Prostaglandin mimetic
Where is the vomiting centre located? What NT is it associated with?
In the brain (past the Blood Brain barrier), and acetylcholine
Where is the Chemoreceptor trigger zone, and why is its location important?
It is located outside the blood brain barrier, and therefore is susceptible to drugs
The CTZ is linked to what, to regulate balance? Via which NTs?
The vestibular apparatus, and via Ach and Histamine
The vomiting centre cannot be induced by drugs but can be induced by…?
Pain
Sight
Smell
Give example of a Acetylcholine muscarinic receptor antagonist used to treat travel sickness
Hyoscine
State three examples of drugs used as a H1 receptor antagonist (Clue: -ine) to counteract sickness (anti-emetic)
Cyclizine
Cinnarizine
Promethazine
What class of drugs are typically used to treat chemotherapy related nausea?
5-HT3 receptor antagonists
