3. drugs used in gastrointestinal disorders.ppt

7/22/2019 3. Drugs Used in Gastrointestinal Disorders.ppt

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Drugs Used in

Gastrointestinal Disorders



Drugs Used in Acid-Peptic Disease

Antacid

React with proton in the lumen of the gut.

The most popular antacid : Mg(OH)2; Al(OH)3

Mg(OH)2

has a strong laxative effect

Al(OH)3 has a constipating action

These drugs are available as single-ingrediantproduct & as combined preparation

The others : calcium carbonate (CaCO3)& natrium

bicarbonate (NaHCO3), but they have a systemiceffects (hypercalcemia, nefrolithiasis, sistemicalkalosis)



Histamin H2 blocker

Prototype : cimetidine, ranitidine, famotidine, andnizatidine

Mechanism of action : pharmacologic antagonists at H2receptors

Effects : reduction of gastric acid secretion

Clinical use :- acid peptic disease

- prevent recurrences of gastric peptic ulcers

- Zolinger-Ellison syndrome (acid hypersecretion, severe

recurrent peptic ulcer, GI bleeding, diarrhea)- gastroesophageal reflux disease (GERD)

Tox : Inhibitor of hepatic drug-metabolizing enzymes andreduce hepatic blood flow, Antiandrogen effects



Antimuscarinic Drugs

Prototype : atropine, methscopolamine,

propantheline, pirenzepin

Mechanism : reduce acid secretion,

reduce cramping and hypermotility in

transient diarrhea

Pirenzepin, the M1 selective inhibitor is

available for the treatment of peptic ulcer

Tox : blockade of thermoregulatory

sweating, salivation, and lacrimation



Sucralfat (alumunium sucrose sulfat)

Binds to injuried tissue and forms a

protective coating over ulcus bed Accelerate the healing of peptic ulcers and to

reduce the recuurence rate

Toxicities is very low

Prostaglandin

Misoprostol, a PGE2 analog use in peptic ulcerassociation with NSAID

Tox : diarrhea, uterine stimulant effects(contraindicated to pregnancy women)



Proton pum inhibitor

Prototype : omeprazole, esomeprazole, lansoprazole,pantoprazole, rabeprazole

Mechanism : inhibitors of the proton pump of gastricparietal cells

Clinical use : peptic ulcer disease associated withH.pylori and with NSAID treatment, Zollinger-Ellisonsyndrome, GERD

Tox : diarrhea, abdominal pain, headache. They canreduce absorption of B12 and certain drugs (digoxin,ketoconazole)

Antibiotics

Prototype : Bismuth (Pepto-bismol), tetracycline, andmetronidazole or amoxicillin+clarithromycin

Clinical use : recurrent peptic ulcer associated withchronic infection of H.pylori



Drugs that Promote Upper GI Motility

Prototype : Metoclopramide, cisapride

Mechanism : stimulate motility GI via cholinergicstimulation (Metoclopramid act as an acetylcholinfacilitator and Dopamine D2 antagonist; Cisapride act as

5-HT4 agonist ) Clinical use : diabetic gastroparesis

Tox :

- parkinsonis, extrapyramidal effects &

hyperprolactinemia (metoclopramide)- arrhythmias (cisapride)



Antiemetic Drugs

Prorotype : metoclopramide, dexamethasone,H1 antihistamine, 5-HT3 inhibitor(ondansetron, granisetron, dolasetron)

Mechanism : Metoclopramide blocking D2receptor in the area postrema

Clinical use : prevention and treatment ofvomiting, especially cancer chemotherapy-

induced vomiting and post operation



Laxative

The drugs that increase bowel movement

Mechanism :

- irritant or stimulant action on the bowel wall (castor oil,

cascara, senna, phenolphtalein, bisacodyl)

- bulk-forming action on the stool that evokes reflex

contraction of the bowel (saline cathartics (Mg[OH] 2 ;

psyllium, methylsellulose)

- Softening action on harding or impacted stool (dioctyl

sodium sulfosuccinate[docusate])

- Lubricating action that eases passage of stool through

rectum (mineral oil, glycerin)



Antidiarrheal Agents

The most effecctive antidiarrheal drugs are

Opioid and derivatives opioid

Prototype : Diphenoxylate, loperamide

Diphenoxylate is formulated withantimuscarinic alkaloids (eg;atropin) to

reduce the likelihood of abuse



Drugs that Inhibit the Formation of

Gallstone

Prototype : chenodiol, ursodiol

Mechanism : chenodiol reduce the secretion

of bile acid by the liver



Drugs Used in Inflammatory Bowel

Disease

5-aminosalicylates

Prototype : sulfasalazine, balsalazine,

mesalamine, olsalamine

Mechanism : they release 5-aminosalicylateacid (5-ASA) in the large intestine, which

inhibits the synthesis of prostaglandine &

inflammatory leukotrients

Corticosteroids

Effect : anti inflammatory



Immunosuppressive agents

Prototype : 6-mercaptopurine, azathioprine,

methotrexate & cyclosporine They are an antimetabolite immunosuppressive

They are the second line agents in the treatment ofsevere IBD or patient with steroid-resistent or –dependent

Tox : bone marrow suppression

Immunosuppressive Response Modifire

Prototype : infliximab

Mechanism : infliximab is a immunoglobulin that binds toTNF and neutralizes its activity

(TNF, a product of monocyte, macrophage & T-cells, isthough to be a critical cytokine in the pathogenesis of

inflammation



Supportive Therapy

Analgesics, anticholinergic and antidiarrheal

agents reducing patient’s symptoms and

improving quality of life Oral iron, folate, vitamin B12

3. drugs used in gastrointestinal disorders.ppt

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