GI system meds Flashcards
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)
Pros and cons of antihisamines
pro-prego catagory B
- All produce drowsiness, dizziness and occasionally confusion; these are typical antihistamine effects. [THE SEDATIVE EFFECTS WILL BE ADDITIVE TO THE EFFECTS OF OTHER CNS DEPRESSANT DRUGS.]
- All have anticholinergic adverse effects including blurred vision, dry mouth, tachycardia, constipation and urinary retention.
- precaution in patients with glaucoma and BPH.
precaution in kids and pts with hx of seizures ( increased risk for paradoxical CNS excitation and seizures)
Promethazine for Motion Sickness
blocks cholinergic receptors in the inner ear-labyrinth-vestibular pathway and dopamine receptors in the brain (presumably in the CTZ).
Disadvantages; Can cause extrapyramidal symptoms; this is an effect of blocking dopamine receptors.
- Being an antihistamine, it can have slight anticholinergic symptoms; blurred vision, tachycardia, dry mouth, constipation, and urinary retention. These adverse effects are more likely in patients who already have a tendency for them (i.e., older adults, patient’s with C.V. disease, patients already on other anticholinergic drugs, etc.)
- Extreme caution iv use extravasation into tissue may result in tissue necrosis.
anticholinergic drugs cause pupillary dilatation which increases intraocular pressure) and patients with seizure disorders (antihistamines can cause paradoxical CNS excitation and seizures).
Scopolamine
Anticholinergic-potent antagonist of muscarinic (cholinergic) receptors in the brain -same neg effects as rest such as no glaucoma, seizures, etc
Phenothiazines
ex:compazine, pheregan
Can be sued for psychosis
possible adverse R:
Extrapyradimal effects, Photosensitivity, tachycardia and hypotension, ; extravasation into tissue may result in tissue necrosis, Suppression of the cough reflex occurs
Dopamine Antagonists
metoclopramide (Reglan)
carefule with pts that have diarrhea.
and Arrhythmias
and seizure disorders
Contraindicated in patients with suspected intestinal obstruction(may lead to intestinal rupture.)
watch for extrapyradmal effects
contraindicated in patients with a history of depression; metoclopramide has increased depression and led to suicide.
Serotonin Antagonists examples
ondansetron (Zofran)
granisetron (Kytril)
dolasetron (Anzemet)
palonosetron (Aloxi)
Drugs for Nausea and Vomiting of Pregnancy
Diclegis (Doxylamine Succinate and Pyridoxine Hydrochloride) 10mg-10mg
Bonjesta (Doxylamine Succinate and Pyridoxine Hydrochloride) 20mg-20mg
Most effective in the management of chemotherapy-induced nausea
Corticosteroids
Drugs for the Treatment of Constipation
Laxatives : bulk-forming agents, surfactants, lubricants, stimulants, saline and osmotic agents–
-Chloride channel activators
Guanylate cyclase C agonists -Serotonin agonists,
Bulk-Forming Agents
bran cereals (Raisin Bran) (All Bran)
psyllium hydrophyllic muciloid (Metamucil) (Modane)
methyl cellulose (Citrucel)
calcium polycarbophil (Fiber-Con)- Contraindicated in patients with esophageal swallowing disorders
Stool softners aka surfactants
calcium docusate (Surfak)
sodium docusate (Colace)
pretty safe for all populations
Lubricants
Mineral oil
-Can decrease the absorption of fat-soluble drugs; they remain in the oil (fat) of the mineral oil and are not absorbed.
- aspiration risk-mjust admin in upright position
-Contraindicated in children under 6 years of age
-Can produce fat soluble vitamin (A,D,E, and K) deficiencies if used for long-term treatment of chronic constipation.
- Not recommended for long-term or daily use for long periods of time
-
Stimulant or Irritant Agents
food (figs) (raisins) (prunes)
natural chem veggie laxative (castor oil)
senna (Sennacot) (Castoria)
bisacodyl (Dulcolax)
harsh laxatives;cramping/diarrhea.
- May cause fluid and electrolyte depletion and/or imbalances
- Commonly causes laxative dependence
Saline Laxatives
magnesium citrate (Citrate of Magnesia)
magnesium hydroxide (Milk of Magnesia)
magnesium sulfate (Epsom Salts)
sodium phosphate (Fleet’s Phospho-Soda)
- Magnesium containing agents= hypermagnesemia; in patients who take excessive drugs and have renal insufficiency
Hypermagnesemia can result in CNS depression
- Significant risk of laxative abuse-
SHORT TERM USE
Osmotic Laxatives
lactulose (Chronulac)
glycerin suppository
sorbitol
mannitol
polyethylene glycol powder (Miralax)
GoLYTELY
—Risk for electrolyte depletion; especially hypokalemia
Chloride Channel Activators-AMITIZA
Effective in relieving chronic idiopathic constipation in men and women
- IBS-C in women
- opioid induced constipation
- elderly population
–EXPENSIVE-
Guanylate Cyclase-C Agonists
linaclotide (Linzess)
plecanatide (Trulance)
-Chronic Idiopathic Constipation in men and women
-IBS-C in men and women
-Contraindicated in less than 6 years of age. Avoid use is those 6-17 years of age. Only indicated in adults.
Seretonin 5-HT4 Receptor Agonists
tegaserod (Zelnorm)-IBS-C-ONLY WOMEN 18-65-CARDIOVASULAR RISK LIKE STROKES-
prucalopride (Motegrity)-CIC
