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Drugs Used in Gastrointestinal Disorders (Pharmacology) - Coggle Diagram
Drugs Used in
Gastrointestinal Disorders
(Pharmacology)
1.Drugs used in acid-peptic diseases
Mucosal protective
agents
Sucralfate
polymerizes at site of tissue damage and protects against further damage; very insoluble with no systemic effects; must be given
4 times daily
Antibiotics
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Proton pump
inhibitors
Pharmacokinetics
Half-lives much shorter
than duration of action
Toxicities, Interactions
Low toxicity - Reduce of stomach acid may reduce absorbtion of some drugs and :arrow_up:that of others
Clinical uses
Peptic ulcer, GERD,
erosive gastritis
Mechanism of Action
Irreversible blockade of H+
/K+ ATPase in active gastric parietal cells
Drugs
Other PPIs: esomeprazole, dexlansoprazole, lansoprazole, pantoprazole, rabeprazole
omeprazole
H2 blockers
cimetidine, famotidine, nizatidine, ranitidine
reduce nocturnal acid but less effective than PPIs against stimulated secretion; very
safe, available over the counter (OTC). Cimetidine, but not other H2 blockers, is a weak antiandrogenic agent and a potent P450 enzyme inhibitor
Antacids
popular OTC medication for symptomatic relief of
heartburn;
not as useful as PPIs and H2 blockers in peptic diseases
8.Pancreatic supplements
Pancrelipase
Mechanism of Action
Replacement enzymes
from animal pancreatic extracts that improve digestion of fat, protein,and carbohydrate
Clinical Applications
Pancreatic insufficiency
due to cystic fibrosis,pancreatitis,
pancreatectomy
Toxicities, Interactions
May increase incidence of gout
Pharmacokinetics
Taken with every meal
Pancreatin
similar pancreatic extracts but much lower potency; rarely used
3.Laxatives
Stimulants:
senna, cascara; stimulate activity; may cause cramping
Chloride channel activators:
lubiprostone, a prostanoic acid derivative, stimulates chloride secretion into intestine, increasing fluid content;
linaclotide, guanylyl cyclase-C agonist, stimulates chloride secretion by CFTR
Bulk-forming:methylcellulose, psyllium, etc
:arrow_up: volume, stimulate evacuation
Opioid receptor antagonists:
alvimopan, methylnaltrexone, block intestinal μ opioid receptors but do not enter CNS, so analgesia is maintained
Magnesium hydroxide, other nonabsorbable salts and sugars
Clinical uses
Simple constipation -bowel prep for endoscopy (especially PEG solutions)
Toxicities, Interactions
Magnesium may be absorbed and cause toxicity in renal impairment
Mechanism of Action
Osmotic agents :arrow_up: water content of stool
Pharmacokinetics
Oral
5.Drugs for irritable bowel syndrome (IBS)
Anticholinergics
nonselective action on GI activity; associated with typical antimuscarinic toxicity
Chloride channel activator
lubiprostone is useful in constipation-predominant IBS in women
Alosetron
Clinical Applications
Severe diarrhea predominant IBS in women
Pharmacokinetics
Oral
Mechanism of Action
5-HT3 receptor antagonist of high potency and
duration of binding -reduce smooth muscle activity in GI tract.
Toxicities, Interactions
Rare but serious
constipation; ischemic colitis -bowel infraction.
2.Prokinetic agents
Domperidone
like metoclopramide but less CNS effect; not available in United States
Cholinomimetics
neostigmine used for colonic pseudo-obstruction in hospitalized patients
Metoclopramide
Clinical uses
Gastric paresis (eg, in
diabetes) -Antiemetic
Pharmacokinetics
Oral and parenteral formulations
Mechanism of Action
D2 receptor blocker :arrow_up:gastric emtying and intestinal motility
Toxicities, Interactions
Parkinsonian symptoms due
to block of CNS D2 receptors
Macrolides
erythromycin useful in diabetic gastroparesis but tolerance develops
9.Bile acid therapy for gallstones
Clinical Applications
Gallstones in patients
refusing or not eligible for surgery
Pharmacokinetics
Oral
Mechanism of Action
Reduces cholesterol
secretion into bile
Toxicities, Interactions
Little or no toxicity
7.Drugs for inflammatory bowel disease (IBD)
Mesalamine
(5-aminosalicylate)
Clinical Applications
Mild to moderately severe
Crohn’s disease and ulcerative colitis
Pharmacokinetics
Various formulations
designed to deliver drug to distal ileum and colon
Mechanism of Action
Mechanism uncertain,may be inhibition of eicosanoid inflammatory mediators
Toxicities, Interactions
Little or no toxicity
Azo compounds
balsalazide, olsalazine, sulfasalazine; colonic bacterial azoreductase enzymes release 5-aminosalicylate in the colon; sulfasalazine
can cause sulfonamide toxicity due to absorption of the sulfapyridine moiety
Glucocorticoids
Immunosuppressant antimetabolites
Anti-TNF drugs
Natalizumab
: antibody that blocks leukocyte integrins; may cause multifocal leukoencephalopathy
6.Antiemetics
Antimuscarinics (eg, scopolamine)
effective in emesis due to motion sickness
Phenothiazines
act primarily through block of D2 and muscarinic receptors
Corticosteroids
mechanism not known but useful in antiemetic IV cocktails
Cannabinoids:
dronabinol is available for use in chemotherapy-induced nausea and vomiting, but is associated with CNS marijuana effects
Other 5-HT3 antagonist antiemetics
: dolasetron, granisetron, palonosetron;
Aprepitant
A neurokinin 1 (NK1) antagonist available for use in chemotherapy-induced nausea and vomiting; associated with fatigue, dizziness,
diarrhea, and P450 interactions
5-HT3 antagonists
(eg, ondansetron)
Clinical Applications
Prevention of
chemotherapy-induced and postoperative nausea
and vomiting
Pharmacokinetics
Oral and parenteral formulations
Mechanism of Action
5-HT3 receptor block in GI and CNS
Toxicities, Interactions
May slow colonic transit
4.Antidiarrheal drugs
Diphenoxylate
similar to loperamide, but high doses can cause CNS opioid effects and toxicity
Colloidal bismuth compounds
subsalicylate and citrate salts available as OTC products; adsorption of toxins has some value in travelers’ diarrhea
Loperamide
Clinical Applications
Nonspecific, noninfectious diarrhea
Pharmacokinetics
Oral
Mechanism of Action
Activates μ opioid receptors in enteric nervous system and slows motility with negligible CNS effects.
Toxicities, Interactions
Mild cramping but little or
no CNS toxicity
Kaolin + pectin:
adsorbent compounds available OTC in some countries