38- drugs used to treat GI disorders Flashcards
what are gastric antacids? (Antacids)
Gastric antacids are weak bases that react with gastric hydrochloric acid to form a salt and water. The net result is increased gastric pH.
Name the active ingredients of antacids? (Antacids)
Calcium carbonate (tums) Aluminum hydroxide Magnesium hydroxide (milk og Magnesia)
List of major side effects of each. (Antacids)
Calcium carbonate´s side effects include nephrolithiasis and fecal compaction.
Aluminium hydroxide reacts with hydrochloric acid to form aluminium chloride, with is insoluble and causes constipation.
Magnesium hydroxide produces magnesium salt, which, because they are poorly absorbed, cause the diarrhea commonly associated with this compound .
What facts increase gastric acids secretion?
Three principal agonists control gastric acid secretion: histamine, acetylcholine and gastrin.
What biochemical mechanism do these three factors share? (H2-receptor blockers)
the final common pathway of these compounds is through activation of the H+/K+ - ATPase proton pump.
How effective are H2-receptor blockers in reducing gastric acid? (H2-receptor blockers)
H2-receptor blockers are capable of reducing more than 90% of basal secretions of gastric acid after a single dose.
Do these agents have additional therapeutic value? (H2-receptor blockers)
They have been shown to be effective in promoting the healing of duodenal and gastric ulcers as well as relieving esophageal reflux disease.
Name four H2.receptor blockers (H2-receptor blockers)
- Cime tidine (Tagamet)-prototype
- Ranitidine (Zantac)
- Famotidine (pepcid)
Nizatidine(Axid)
How can H2-blockers be given? (H2-receptor blockers)
IV or PO
What are the side effects of H2-receptor blockers?
In genral they are well tolerated longest clinical experience is with cimetidine, but the other drugs associated with this class are similar. Most common side effects include nausea headache, dizziness. Cimetidline is known to create unwanted endocrinological effects such as gynecomastia and elevated serum prolactin levels (resulting in galactorrhea). Confusional states in the elderly may be seen.
Are there any important drug-drug interactions associates with H2-blockers? (H2-receptor blockers)
Yes. Cimetidine is a strong inhibitor of cytochrome p-450 system and therefor can slow the metabolism of drugs normally broken down through this system. Examples include warfarin, quinidine, benzodiazepine, procainamide, and phenytoin.
Name five prion pump inhibitors(Proton pump inhibitors)
Omeperazole (Prilosec)-prrototype Lansoprazole (Prevacid) Rabeprazole (aciphex) Pantaoprazole (protonix) Esomeprazole (Nexium)
Explain how these drugs work. (Proton pump inhibitors)
these drugs become active in an acidic environment and irreversibly inhibit the H+/K+- ATPase proton pump on the luminal surface of parietal cells.
When would administering this type of drug be useful? (Proton pump inhibitors)
for patients with esophageal reflex, duodenal or gastric ulcer, multiple endocrine neoplasia (MEN), or a hypersecretory condition such as Zollinger - Ellison syndrome. Also used in combination with antibiotics to eradicate H. pylori
How effective are proton pump inhibitors?(Proton pump inhibitors)
they can inhibit 100% of gastric acid secretion with a singe daily dose.
How are the potential side effects?(Proton pump inhibitors)
most commonly these drugs are well tolerated but they can cause nausea or diarrhea. in animal (not human) studies, long-term administration of large doses of omperazole has caused development of gastric carcinoid tumors.
How are they administrated? (Proton pump inhibitors)
PO og IV
Name the drugs belonging to this class. (Mucosal protective agents)
Sucralfate (carafate)
Bismuth
Misoprostol (Cytotee)
What is Sucralfate?
sucralfate is a sulfated disaccharide developed for use in treating peptic ulcer disease.
What is its major mechanism of action? (Sucralfate)
polymerization and selective binding to necrotic ulcer tissue, where it acts as a barrier to acid , pepsin and bile.
what other action is possible? (Sucralfate)
Sucralfate may also directly absorb bile salts and may stimulate endogenous prostaglandin synthesis.
can sucralfate be taken with H2.receptor blockers or proton pump inhibitors? (Sucralfate)
No. Sucralfate requires an acid pH to be activated and should not be administered simultaneously with either H₂-receptor blockers or proton pump inhibitors.
Bismuth: How does bismuth work?
Like sucralfate, bismuth compounds appear to work by selectively binding to an ulcer, coating it and protecting it from acid and pepsin.
What other therapeutic actions are possible? (Bismuth)
Bismuth compounds may have some antimicrobial activity against H. pylori. When bismuth compounds are combined with antimicrobials (metronidazole and tetracycline), ulcer healing rates of up to 98% have been reported.
Misoprostol: How does this drug work?
Misoprostol is a prostaglandin E1 analog that may stimulate gastric secretion of mucus and bicarbonate.
What are the clinical indications for administering misoprostol? (Misoprosol)
Currently is s seldom use because of its adverse effects and minimal benefits. In the past it was used for peptic and duodenal ulcers included by long-term NSAID therapy.
What are its major side effects? (misoprosol)
Diarrhea in up to 30% of patients who take the drug, unwanted uterine contractions (contraindicated in pregnancy) , and exacerbations of inflammatory bowel disease.
Prokinetic Agents: What conditions can be treated with prokinetic agents?
Gastroesophageal reflux and gastroparesis
Name two drugs in this class.(Prokinetic Agents)
- Cisapride (Propulsid)
2. Metoclopramide (Reglan)
Cisapride: How does cisapride work?
It stimulates the release of acetylcholine at the myenteric plexus, which results in increased esophageal sphincter tone and therefore decreased reflux.
What are its toxicities?
prolonges QT interval and cardiac arrhythmias - generally no longer available in the US because of these severe adverse effects. can only be used ny patients who have failed all. other treatments and have undergone an ECC.
Metoclopramide: Which receptors does metoclopramide stimulate?
5-HT₃ and D₂ receptors in gastric smooth muscle, which results in acceleration of GI emptying. it is a first-line agent. words primarily on the small intestine.
What types of adverse effects can be seen with this drug? (Metoclopramide)
Extrapyramidal side effects are the most important (parkinsonism and tardive dyskinesia)
- Diarrhea
- Drowsiness
Antiemetic Drugs: State the major categories of antiemetics and give and example of each.
- H₁ antihistamines: diphenhydramine
- Phenothiazines: prochlorperazine (Compazine)
- Marijuana: dronabinol (Marinol)
- 5-HT₃ inhibitors: ondansetron (Zofran)
- corticosteroids - d’esamethasone
- Benzamides - metoclopramide
What are the clinical indications for these drugs? (Antiemetic Drugs)
Any condition that is inducing emesis, such as chemotherapy of GI infection.
into what two major subtypes is IBD usually divided?(IBD)
Ulcerative colitis Crohn´s disease
What are the pharmacological options for trading these diseases? (IBD)
sulfasalazine antibiotics (metronidazole, ciprofloxacin) glucocorticoids, immunosuppressive agents such as azathioprine, methotrexate, and cyclosporine and immunomodulators such as infliximab. Glucocoticoids, antibiotics and immunosuppressive agents are discussed in greater detail elsewhere in the text but are mentioned here for completeness.
how does it work? (sulfasalazine)
sulfasalazine supresses proinflammatory mediators such as IL - and TNF-α. its exact mechanism of action is still under investigation.
what conditions is is used to treat? (sulfasalazine)
it works much better against the symptoms of ulcerative colitis than Crohn´s disease, since Crohn´s often involves the small bowl, where the drug is not active.
What are the side effects? (sulfasalazine)
Vomiting diarrhea, nausea
when should sulfasalazine not be prescribed? (sulfasalazine)
because sulfasalazine also has a sulfonamide component, it should be avoided in patients with sulfa allergies.
What is it? (Infliximab)
is is a monoclonal anybody target to tumor necrosis factor alpha (TNF-α), … of the inflammation in Crohns disease.
when is it used? (Infliximab)
to treat IBD, particularly moderate to severe chins disease. it is particularly good for closing fistulas associated with crowns disease and acute flares of this condition. Also used for rheumatoid arthritis.
what are its toxicities? (Infliximab)
respiratory infection and hypotension. since infliximab is given IV, acute reactions such as fever, chills, and urticaria may occur after infusion. also antibodies to infliximab may develop.
Name two agents widely used for this purpose. (Antidiarrheal agents)
Loperamide (imodeium)
Diphenoxylate (Lomotil)
How to they work?
Loperamide and diphenoxylate are derivatives of meperidine, an opiate, with slows gastrointestinal utility through actions of peripheral u-potential receptors. there drugs ave fry few is any CNS effects.
How are laxative classified? (Laxatives)
these drugs are generally classified by simplified mechanism of action, that is a stimulants, osmotic agents, bulking agents and stool softeners.
give some examples of stimulant laxatives. (stimulant)
Castor oil
senna (senekot)
Phenolphtalein (Ex-Lax)
Bisacodyl (Dulacolax)
what are the side effects of stimulant laxatives? (stimulant)
chronic stimulation of the colon can leas to chronic discretion and thus perpetuation of the perceived need for laxatives.
name some of this group. (Bulking agents)
these agents which are usually insoluble during the digestive process, include: hydrophilic colloids (from indigestible parts of fruits and vegetables)
agar
methylcellulose
bran
how do these agents work?
they are non absorbable agents that increase water retention and stool bulk. this distends the bowl and stimulates peristalsis.
name two agents in this group. (Osmotic agents)
saline cathartics (magnesium citrate and magnesium hydroxide) non digestible sugars such as lactulose and sorbitol
how dot they work? (Osmotic agents)
the osmotically draw water into the lumen of the digestive tract, which then stimulates motility.
how do these agents work? (stool softeners)
by emulsifying stool, these agents soften it and make its paddle easier.
name some stool softeners. ((stool softeners)
examples include mineral oil and docusate sodium (colace)
