PHARM - Drugs Used in Gastrointenstinal Disorders - Week 6 Flashcards
What two nerves form the parasympathetic innervation to the GI tract? Is it inhibitory, stimulatory, or both?
Craniosacral:
-Vagus nerve
-Pelvic nerve
Stimulatory
What nerve form the sympathetic innervation to the GI tract? Is it inhibitory, stimulatory, or both?
Thoracolumbar:
Prevertebral ganglia
Inhibitory
Name 8 general causes of vomiting.
Unpleasant smells Unpleasant sights Strong emotions Pain Headache/migraine Abnormal motion Toxins GIT irritation
What 4 signalling molecules are involed in vomiting?
Acetylcholine, dopamine, serotonin, and histamine
What kinds of drugs can be used to reduce the urge to vomit based on the signalling molecules involved (4)?
Antihistamines
Dopamine antagonists
Serotonin antagonists
Muscarinic receptor antagonists
Name 4 side effects of using a sopamine receptor antagonist.
Increased gastric emptying, restlessness, anxiety, drowsiness
Define 5HT3 what kind of nausea 5HT3 receptor antagonists are used for (2).
5HT3 is serotonin
5HT3 receptor antagonists are used to vomiting associated with chemotherapy and post-operative management
Do 5HT3 receptor antagonists have few or many antagonists?
Few
What form of nausea do antihistamines treat?
Motion sickness induced nausea
Name two side effects of antihistamines.
Sedation and drowsiness
What form of nausea do muscarinic receptor antagonists treat?
Motion sickness induced nausea
Name three side effects of muscarinic receptor antagonists.
Constipation, dry mouth, and tachycardia
What two substances do mucous neck cells in the stomach produce?
Mucus and bicarbonate
What two substances do parietal cells in the stomach produce?
Gastric acid and intrinsic factor for Ca2+ absorption
What substance does enterochromaffin-like cells in the stomach produce and what does it do?
Histamine which stimulates acid
What two substances do chief cells in the stomach produce?
Pepsinogen and gastric lipase
What substance do D cells in the stomach produce and what does it do?
Somatostatin which inhibits acid
What substance do G cells in the stomach produce and what does it do?
Gastrin which stimulates acid
Consider the following receptors in the stomach, and whether or not they stimulate or inhibit HCl production: Histamine receptor Muscarinic receptor Gastrin receptor Somatostatin receptor Prostaglandin receptor
Histamine receptor - stimulatory Muscarinic receptor - stimulatory Gastrin receptor - stimulatory Somatostatin receptor - inhibitory Prostaglandin receptor - inhibitory
Describe briefly how parietal cells produce HCl.
Is a proton pump that uses ATP to exchange K+ from the lumen for a H+ ion. Once in the lumen, the H+ forms HCl.
What can cause oesophagitis.
Acid reflux
What causes an oesophageal stricture?
Narrowed tube
What three effects do antacids have?
Neutralises HCl, binds bile acid, and decreases pepsin activity.
Name 4 general ingredients of antacids.
Aluminium hydroxide
Calcium carbonate
Magnesium salts
Sodium bicarbonate
What effect do magnesium and aluminium have on the bowels? Should they be taken apart or together?
Magnesium - increased bowel motility
Aluminium - decreased bowel activity
They should be taken together
What do -tidine drugs (affix) do?
Are histamine receptor antagonists that reduce acid secretion by parietal cells.
What do -prazole drugs (affix) do? What kind of environment is required for them to activate? Do they bind reversibly or irreversibly?
Are prodrugs that require activation in an acidic environment.
They bind irreversibly to the proton pump of parietal cells.
What is an advantage of -prazole drugs?
It will reduce acid secretion independently of how secretions stimulated
Are cytoprotective drugs common? What are they and what are they used for?
Prostaglandin analogues that are rarely used. Used to treat ulcers.
Name 4 drugs that can directly irritate the oesophagus, cause strictures, and affect acid production.
NSAIDs
Bisphosphonates
Antibiotics (tetracyclines and doxycycline)
Iron supplements
What bacteria is a main cause of ulcers? What is it a risk factor for?
Helicobacter pylori
Risk factor in the development of gastric carcinoma
If an ulcer is caused by H. pylori, what is the first line treatment? What does success depend on?
Eradicating H. pylori
Combination therapy of proton pump inhibitors and antibiotics is neccessary
Success depends on adherence to the treatment
What happens with too little and too much bowel motility?
Too little - constipation
Too much - diarrhoea
Define constipation and give three possible causes.
Difficult faecal evacuation as a result of hardness or infrequent movements
- lifestyle/diet related
- medically related
- adverse effect from a drug
Name 4 agents that can be used to alleviate constipation.
Softeners (coats faeces) Bulk forming agents (psyllium) Stimulants (increased peristalsis) Osmotics (increases lumen fluid volume)
What are prokinetics? What kinds of drugs are they?
They are motility stimulating drugs. They are dopamine receptor antagonists.
Are opioids motility increasing or decreasing drugs?
Increasing
What do anti-spasmodics do?
Smooth muscle relaxant, reducing GI motility and spasm
Do antispasmodics cross the blood-brain barrier?
No
Are opioids for GI motility used short term or long term? Can they be administered to children?
Short term only
Not to be used in children
Name three classes of drugs that can be used to treat inflammatory bowel disease.
Corticosteroids
5-aminosalicylates
TNF-alpha antagonists
They are all anti-inflammatory
