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7/30/2019 Pharmacology of the G.I.T
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Drugs used in
Gastro-intestinal system
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Treatment of peptic ulcer
Anti emetics
Laxatives Anti diarrhea
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Pharmacology of the GIT
The mouth
a proper flow of saliva is necessary to keep the mouthfresh & free from infection.
Salivary flow will be diminished in fever, dehydration ,&
by certain drugs.
Several oral infection may supervene if salivary flow ismarkedly decreased.
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DISEASES OF THE MOUTH
CANDIDIASIS :The yeast Candidaalbicansis a normal mouth commensalbut it may proliferate to cause thrush.
White patches are seen on the tongueand buccal mucosa. A clinical diagnosis issufficient to instigate therapy, althoughbrushings or biopsies can be obtainedfor mycological examination.
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Oral thrush is treated using nystatin oramphotericin suspensions or lozenges.Resistant cases or immunosuppressedpatients may require oral fluconazole.
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Parotitis is due to viral or bacterial
infection
Bacterial parotitis usually occurs as a
complication of major surgery. It is a
consequence of dehydration and poor oral
hygiene and can be avoided by good post-
operative care
Broad-spectrum antibiotics are required,
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Prevention of oral infection
1. Avoid oral infection during surgery
2. Avoid dehydration
3. Use mouthwashes
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The major components of mouthrinses:
1. Water: the major vehicle to solubilize theingredients.
2. Flavoring: is designed to make mouthrinsepleasant to use.
3. Humectant: to prevent crystallization around
the opening of the container.
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4.Surfactant: to solubilize the flavoring agent &provide foaming action.
5. Alcohol is also helps solubilize some of theingredients present in the formulation.
6. Active ingredients vary within the productcategory antimicrobial agents, fluoride, &chlorophyllins
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Chlorophyllins can serve as topicaldeodorizers to mask halitosis.
Fluoride rinses will reduce cariouslesions.
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chlorhexidine broad spectrumantibacterialagent
Depending on the dose, it can interfere withbacterial cell wall transport or disrupt thecell wall.
Is used in 0.2% solution , the mouth is rinsed2 to 3 times daily with about 10 ml for 1minute.
The tongue & teeth may be stained brown butthis can be avoided by brushing the teethbefore use.
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General dosing information:
The usual adult dose is 10-20 ml. the duration
of rinsing varies depending on the type ofagent used.
The maximal dose for each patient must beindividualized depending on factors as age,physical status, ability to effectively rinse &expectorate, oral health & sensitivity.
Mouthwashes are often not prescribed foryoung pediatrics.
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Patient advise
To receive the greatest antiplaque oranticaries benefit, the patient should rinsebefore retiring to bed
After using the mouthwash , the patientshould not rinse with water or drink anythingfor at least 30 minutes, immediately drinkingor rinsing with water will increase the drug
clearance from the mouth & reduce itseffectiveness.
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P l D
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Peptic Ulcer Disease
Definition
Break & discontinuity of the mucosa of thestomach or duodenum, penetrating into muscularismucosa
Factors
1. Infection with Helicobacter Pylori (H.Pylori)
2. Increased HCL secretion
3. Inadequate mucosal defense against gastricacid
4. Other factors: smoking, NSAIDs, alcohol
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Peptic Ulcer Disease
In peptic ulcer (PU) thereis imbalance between:
The damaging factors:
gastric acid, pepsin, H.pylori& NSAIDs.
The protective factors:prostaglandins, mucus,bicarbonate & mucosalblood flow.
Protective
factors
Aggressive
factors
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Treatment:
Aim
1. Symptomatic relief
2. Prevent relapse
3. Prevent complication
Non pharmacological approaches
1. Stop smoking
2. Avoid alcohol3. Stop the use of ulcerogenic drugs (NSAIDs)
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Pharmacological
1. Eradicate H.Pylori
2. Reduce or neutralize the acid3. Protect the gastric mucosa from damage
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Drugs used in the treatment of PU
Drugs that neutralize gastric acidityAntacids
Drugs that decrease gastric acid secretionH2 blockers
PPIAntimuscarinic
Mucosal protective agents
SucralfateMisoprostol
Colloidal Bismuth compounds
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Eradication of Infection
H.Pylori adapted to live in the mucus thatoverlies gastric epithelial cells & mucosa inthe duodenum
This Gram -ve bacteria may cause pepticulcer by impairing mucosal defense viaelaboration of toxins & enzymes, by
provoking local inflammatory response.
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H. pylori
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Optimal therapy of patient with peptic ulcer(duodenal & gastric ulcers) who are infected with
H. Pylori requires antimicrobial treatment
Various drug combination which are effective:
Omeprazole (antisecretory)
Antibiotic like Clarithromycin, Amoxicillin, Tetracycline& Metronidazole
Triple therapy
RegimenOmeprazole or Lanzoprazole + Amoxicillin +
Clarithromycin.
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Eradication of H.Pylori results in rapid healing of active pepticulcer & low recurrence rates (less than 15% compared to 60 to100% per year for patients used traditional antisecretory
agents)
2. Reduction of Acidity
This can be done by inhibit H+ secretion or
neutralize H+ Gastric acid secretion by parietal cells of the
gastric mucosa is controlled by:
1. Acetylcholine2. Histamine they stimulate H+
3.Gastrin
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4. Prostaglandins (PGs) E2 & I2 inhibit acid secretion,stimulate mucus & bicarbonate secretion.
A. Drugs Used to Inhibit H+ Secretion
1.Histamine antagonists (H2-receptorantagonists)
MOA: blocks histamine receptors
inhibit H+secretion
Examples: Cimetidine, Ranitidine
Indications:
1. Peptic ulcer
2. Gastroesophageal reflux disease
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Unwanted effects are rare.
Cimetidine sometimes gynaecomastia in men &rarely, a decrease in sexual function.
Cimetidine also inhibits cytochrome P450 andretard metabolism of a range of drugs.
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2.Proton Pump Inhibitors (PPIs)
MOA: bind to H+/K+ -ATPase enzyme system,
suppressing secretion of H+ ions into gastriclumen
Examples: Omeprazole, Lanzoprazole
Indications:
1.As one component of therapy for eradication ofH.Pylori.
2.Treatment of NSAIDs induced ulcer.
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3. Anti-muscarinic DrugsSpecific muscarinic M1-receptor antagonists:
Pirenzepine
Antacids They are weak bases, they reduce gastric acidity by
neutralization
Antacid + HCl salt + water
Commonly used antacids are salts of Aluminum &Magnesium as Al(OH)3, Mg(OH)2 either alone or incombination; NaHCO3, CaCO3 also used
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Therapeutic uses:
For symptomatic relief of peptic ulcer disease & GRED
S/Es:
1. Mg-containing antacids cause diarrhea
2. Al-containing antacids cause constipation
3.NaHCO3 librates CO2 causing belching & flatulence.
Should not be given to patients who are on a sodium-
restricted diet.
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B. Mucosal Protective Agents1.Sucralfate
It is combination of Al salts & sulfated sucrose
MOA:In acidic medium, it forms complex gel with mucus, so
creates a physical barrier that impairs diffusion ofHCL
Sucralfate should not be administered with antacids,H2-antagonists or PPIs
S/Es: Constipation
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2.Misoprostol
MOA
Stable analogue of PGE1, it inhibit gastric acid secretion
It is used to prevent gastric damage that canoccur with chronic use of NSAIDs
S/Es: Diarrhea, Uterine contraction may occur
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emetic Agents-Anti
Nausea & vomiting may occur in variety of
conditions, for examples:
1. Motion sickness
2. Hepatitis
3. Chemotherapeutic agents4. Pregnancy
Uncontrolled vomiting can produce dehydration,metabolic imbalance & nutrients depletion
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Receptors mediate emesis:
1. Histamine receptors [H1]2. Dopamine receptors [D2]
3. 5-HT3 (serotonin) receptors
4. Muscarinic receptors
Anti-emetic classified as antihistamine,anticholinergic, anti-dopaminergic, anti-5-HT3drugs
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exampleDrug class
MetoclopramideD2-receptor antagonists
CyclizineHistamine [H1] Receptor
AntagonistsOndansetron5-HT3 Receptor Antagonists
HyoscineAntimuscarinic Agents
DexamethasoneCorticosteroids
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Metoclopramide
MOA:1. Centrally block D2 receptors / in CTZ
2. Peripherally it is prokinetic agent, it
accelerates gastric emptying [cholinergic effect]
Given orally or by injection
S/Es
Peripheral: Abdominal cramps
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Disorders of the Lower GI Tract
Constipation
Diarrhea
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GI Motility
http://img.tfd.com/vet/thumbs/gr294.jpg
increased transit time
- Increased waterabsorption constipation
decreased transit time
-Decreased water and
nutrient absorption diarrhea
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Antidiarrheal Agents
Diarrhea: frequent passage of liquid feces
Pathophysiology of diarrhea1. motility of GIT
2. secretion of fluid into GIT lumen
3. fluid absorption in the intestine
Causes of diarrhea
1. Infections
2.Toxins
3.Drugs
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Treatment
1.Maintenance of fluid & electrolyte balanceOral rehydration is the 1st priority
2. Use of Anti-infective agents
3. Use of Non-antimicrobial Antidiarrheal agents(Antimotility)
a. Antimuscarinic agents
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b. Opiates1. Codeine
2. Loperamide
S/Es of antimotility agents: constipation.
P (l )
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Purgatives (laxatives)
Constipation: refers to bowel movements
that are infrequent and/or hard to pass Causes:
1. Pregnancy2. Drugs
3. Elderly patients4. Diet contents
Treatment:1. Remove the cause2. Accelerate the movement of food through
GIT by several methods:
is discouragedlaxativesThe routine use of
http://en.wikipedia.org/wiki/Bowel_movementhttp://en.wikipedia.org/wiki/Bowel_movement7/30/2019 Pharmacology of the G.I.T
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is discouraged,laxativesThe routine use ofas having bowel movements may come to be
dependent upon their use.
Examples
Classes
MethylcelluloseBulk laxatives
LactuloseOsmotic laxatives
GlycerinsuppositoriesFecal softener
BisacodylStimulantPurgatives