GI system meds Flashcards
(42 cards)
What kind of drugs treat stomach acid disorders?
antacids, histamine-2 (H-2) receptor antagonists, and proton-pump inhibitors
Antacids how do they work?
in the lumen of the stomach they neutralize gastric acid and prevent the acid-stimulated activation of the gastric enzyme, pepsin, which participates in gastric mucosal injury.
-not absorbed
Disadvantages of the Antacids
-Can delay the diagnosis of more serious GI problems
-Can result in an acid-base imbalance(metabolic alkalosis)
-Excessive absorption of cations can result in serum electrolyte imbalances and their specific adverse effects:
Hypernatremia - water retention, hypertension, worsening of CHF
- Hypercalcemia - constipation, nephrolithiasis, increased secretion of HCl acid
- Hypermagnesemia - diarrhea, neurotoxicity, arrhythmias
-Hyperaluminemia - constipation, neurotoxicity, delayed gastric emptying
Antacids examples
- aluminum hydroxide
- magnesium hydroxide
- calcium carbonate
- sodium bicarbonate
TUMS, Milk of Magnesia
Alka-Seltzer,Maalox, Mylanta
H-2 Antagonists (H-2 Blockers) examples
cimetidine (Tagamet)
famotidine (Pepcid)
nizatidine (Axid)
ranitidine (Zantac)
H-2 blockers how do they work?
selective antagonists of histamine on H-2 receptors
Histamine=natural agonist on H-2 receptors and stimulates increased secretion of HCl acid. The H-2 blockers inhibit this mechanism of gastric acid secretion and raise gastric pH.
Why is Cimetidine unique
it also is an inhibitor of Cytochrome P-450 enzymes in the liver
Cimetidine disadvanages
Can inhibit the hepatic metabolism of other drugs that are metabolized in the liver; Cimetidine is a hepatic enzyme inhibitor and can cause potentiative pharmacokinetic drug-drug interactions with the other drugs.
- Can cause gynecomastia and hypospermia; this is a result of the antiandrogenic effects of cimetidine.
- May rarely cause blood dyscrasias; thrombocytopenia, agranulocytosis, anemia.
Proton Pump Inhibitors examples
dexlansoprazole (Dexilant)
esomeprazole (Nexium) OTC
lansoprazole (Prevacid) OTC
omeprazole (Prilosec) OTC
pantoprazole (Protonix)
rabeprazole (AcipHex)
PPI’s how do they work?
they block the enzyme in responsible for production and release of hydrogen ions (and HCL acid). By this mechanism, all of the possible stimuli (histamine, gastrin, and cholinergic stimulation) to the production of HCl acid are effectively blocked and these drugs are the most effective agents in reducing gastric acid production and elevating gastric pH.
Advantages of the Proton-Pump Inhibitors
-Most effective acid-reducing drugs; by blocking all three of the stimulatory mechanisms for HCl production, they are most effective in reducing the free acid in the stomach.
- Very useful for gastroesophageal reflux disease (GERD); they are also used for peptic ulcer disease and Zollinger-Ellison syndrome (tumors that produce gastrin, causing excessive ulceration).
Disadvantages of the Proton-Pump Inhibitors
max 8-12 weeks; suppressive effect they have on gastric acid secretion. beyond 3 months refer patient to endoscopy
- Alters the absorption of other orally administered drugs;
- Commonly causes dizziness, headache, diarrhea
- Inhibits dietary protein digestion; [Note: Acid plays a vital role in the initial digestion of dietary protein.]
- Possibly causes an overgrowth of gastric bacteria and yeast (candida); this is because of the loss of the normally inhibitory effects of HCl acid on gastric bacterial growth.
Cytoprotective Agents example
sulcralfate (Carafate)
misoprostol (Cytotec)
Misoprostol
prodrug - Prostaglandin E-1 is a naturally occurring biomediator that does many things in the body like stimulation of the production of protective gastric mucus and stimulation of uterine contractions
some drugs (NSAIDs) inhibit prostaglandin synthesis and prevent the production of gastric mucus. Misoprostol is administered together with them to supply the necessary amount of prostaglandin to ensure that gastric mucus is still produced.
misoprostol = less gastric acid production
Misoprostol and women
-Pregnancy tests are required
-Pregnancy Category X drug - Contraindicated in pregnancy
*used in obstetrics as a labor inducer at the time of delivery. This use does not fall into the Pregnancy Categories because it is intentionally administered at an appropriate time to deliberately cause uterine contractions
Opiate Antidiarrheal Drugs examples
difenoxin-atropine (Motofen)
diphenoxylate-atropine (Lomotil)
loperamide (Imodium)
Disadvantages of Using the Opiate Antidiarrheal Drugs
Can cause CNS sedation
-precaution in patients with liver disease
-Contraindicated in infectious diarrhea; can cause retention of bacterial irritants which are then more extensively absorbed and may make the patient sicker for a longer period of time.
Absorbent Drug for the Treatment of Diarrhea
bismuth subsalicylate (Pepto-Bismol) (Kaopectate) (Maalox Total Relief)
Quick absorbent drug facts-
Bismuth subsalicylate has been reported to cause Reye’s Syndrome (salicylates)
- Less effective than the opiate antidiarrheal drugs
- Bismuth can turn the tongue and stool black; can be confused with GI bleeding
- Bismuth contains salicylates; may cause salicylism; may interact with warfarin to increase bleeding tendency; avoid in patients with aspirin allergy or contraindications to aspirin
Quick absorbent drug facts-
Bismuth subsalicylate has been reported to cause Reye’s Syndrome (salicylates)
- Less effective than the opiate antidiarrheal drugs
- Bismuth can turn the tongue and stool black; can be confused with GI bleeding
- Bismuth contains salicylates; may cause salicylism; may interact with warfarin to increase bleeding tendency; avoid in patients with aspirin allergy or contraindications to aspirin
Special” Antidiarrheal drugs examples
eluxadoline (Viberzi)
alosetron (Lotrenex)
Eluxadoline (Viberzi) is
mu and kappa opioid receptor agonist and a delta opioid receptor antagonist affinity for opioid receptors of the gut. This specificity can reduce abdominal pain and diarrhea in patients with IBS-D without the constipating side effects
Alosetron (Lotrenex) is
potent 5-HT3 (serotonin) receptor antagonist approved for use in females with severe diarrhea predominant IBS.
Antihistamines for Motion Sickness Nausea
diphenhydramine (Benadryl)
meclizine (Antivert) (Bonine)
dimenhydrinate (Dramamine)
