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Drugs Used in GastrointestinalDisorders

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Drugs Used in Acid-Peptic DiseaseDrugsUsed in Acid-Peptic Disease

AntacidReact 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 actionThese drugs are available as single-ingrediantproduct & as combined preparation

The others : calcium carbonate (CaCO 3)&natrium bicarbonate (NaHCO 3), but they havea systemic effects (hypercalcemia,nefrolithiasis, sistemic alkalosis)

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Histamin H2 blockerPrototype : cimetidine, ranitidine, famotidine, andnizatidineMechanism of action : pharmacologic antagonistsat H2 receptorsEffects : reduction of gastric acid secretionClinical 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-metabolizingenzymes and reduce hepatic blood flow,

Antiandrogen effects

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Antimuscarinic DrugsPrototype : atropine, methscopolamine,propantheline, pirenzepin

Mechanism : reduce acid secretion, reducecramping and hypermotility in transient diarrheaPirenzepin, the M1 selective inhibitor is availablefor the treatment of peptic ulcer

Tox : blockade of thermoregulatory sweating,salivation, and lacrimation

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Sucralfat (alumunium sucrose sulfat)Binds to injuried tissue and forms a protectivecoating over ulcus bed

Accelerate the healing of peptic ulcers and to

reduce the recuurence rateToxicities is very low

ProstaglandinMisoprostol, a PGE2 analog use in peptic ulcerassociation with NSAIDTox : diarrhea, uterine stimulant effects(contraindicated to pregnancy women)

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Proton pum inhibitorPrototype : omeprazole, esomeprazole,lansoprazole, pantoprazole, rabeprazoleMechanism : inhibitors of the proton pump ofgastric parietal cellsClinical use : peptic ulcer disease associated withH.pylori and with NSAID treatment, Zollinger-Ellison syndrome, GERDTox : diarrhea, abdominal pain, headache. Theycan reduce absorption of B12 and certain drugs(digoxin, ketoconazole)

AntibioticsPrototype : Bismuth (Pepto-bismol), tetracycline,and metronidazole or amoxicillin+clarithromycinClinical use : recurrent peptic ulcer associatedwith chronic infection of H.pylori

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Drugs that Promote Upper GI MotilityPrototype : Metoclopramide, cisaprideMechanism : stimulate motility GI viacholinergic stimulation (Metoclopramid act asan acetylcholin facilitator and Dopamine D2antagonist; Cisapride act as 5-HT4 agonist )Clinical use : diabetic gastroparesis Tox :

- parkinsonis, extrapyramidal effects &hyperprolactinemia (metoclopramide)- arrhythmias (cisapride)

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Antiemetic DrugsProrotype : metoclopramide, dexamethasone, H1antihistamine, 5-HT3 inhibitor (ondansetron,granisetron, dolasetron)Mechanism : Metoclopramide blocking D2

receptor in the area postremaClinical use : prevention and treatment ofvomiting, especially cancer chemotherapy-induced vomiting and post operation

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LaxativeThe drugs that increase bowel movementMechanism :- irritant or stimulant action on the bowel wall(castor oil, cascara, senna, phenolphtalein,bisacodyl)- bulk-forming action on the stool that evokesreflex 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 stoolthrough rectum (mineral oil, glycerin)

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Antidiarrheal AgentsThe most effecctive antidiarrheal drugs are Opioidand derivatives opioidPrototype : Diphenoxylate, loperamide

Diphenoxylate is formulated with antimuscarinicalkaloids (eg;atropin) to reduce the likelihood ofabuse

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Drugs that Inhibit the Formation ofGallstone

Prototype : chenodiol, ursodiolMechanism : chenodiol reduce the secretion ofbile acid by the liver

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Drugs Used in Inflammatory BowelDisease5-aminosalicylates

Prototype : sulfasalazine, balsalazine,mesalamine, olsalamineMechanism : they release 5-aminosalicylate acid(5-ASA) in the large intestine, which inhibits thesynthesis of prostaglandine & inflammatoryleukotrients

CorticosteroidsEffect : anti inflammatory

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Immunosuppressive agentsPrototype : 6-mercaptopurine, azathioprine,methotrexate & cyclosporineThey are an antimetabolite immunosuppressiveThey are the second line agents in the treatment of

severe IBD or patient with steroid-resistent or dependentTox : bone marrow suppression

Immunosuppressive Response Modifire

Prototype : infliximabMechanism : infliximab is a immunoglobulin that bindsto TNF and neutralizes its activity(TNF, a product of monocyte, macrophage & T-cells,is though to be a critical cytokine in the pathogenesisof inflammation

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Supportive Therapy Analgesics, anticholinergic and antidiarrhealagents reducing patients symptoms andimproving quality of lifeOral iron, folate, vitamin B12