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1 GASTRO-INTESTINAL DRUGS. 2 GI Drugs Drugs for: – Peptic ulcers – GERD – Emesis – Motility Disorders Diarrhea constipation.

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Presentation on theme: "1 GASTRO-INTESTINAL DRUGS. 2 GI Drugs Drugs for: – Peptic ulcers – GERD – Emesis – Motility Disorders Diarrhea constipation."— Presentation transcript:

1 1 GASTRO-INTESTINAL DRUGS

2 2 GI Drugs Drugs for: – Peptic ulcers – GERD – Emesis – Motility Disorders Diarrhea constipation

3 3 Peptic Ulcer Drugs The Problems – Infection with H. pylori – Increased HCl secretion – Inadequate mucosal defense Solutions: – Antimicrobials (amoxicillin) – H2- histamine blockers(Cimetidine) – Prostaglandins (Misoprostol) – Proton pump inhibitors (Omeprazole)

4 4ANTIMICROBIAL Amoxicillin Metronidazole Tetracycline Clarithromycin Triple therapy: PPI + Metronidazole or amoxicillin + clarithromycin Quadruple therapy: Bismuth sub + metronidazole + tetracycline + PPI or H ₂- receptor antagonist

5 5 ADJUNCT MANAGEMENT REST, RELIEVE STRESS STOP/REDUCE SMOKING/DRINKING Inclination of the bed head at 45 degrees DIET – NON-IRRITATING – FREQUENT

6 Regulation of gastric acid secretion Gastric acid secretion by parietal cells of the gastric mucosa is stimulated by acetylcholine, histamine and gastrin. The binding of AcH, gastrin and histamine to their various receptors results in the activation of protein kinases which in turn stimulates the H ⁺ /K ⁺-ATPase proton pump to secrete hydrogen ions in exchange for K⁺ into the lumen of the stomach Gastrin and AcH act by inducing an ↑ in calcium level While receptor binding of prostaglandin E₂ and somatostatin inhibits adenylyl cyclase 6

7 7

8 8 H2 RECEPTOR BLOCKERS Cimetidine Ranitidine Famotidine Nizatidine

9 9 Mech Of Action:H2 receptor antagonists competitively inhibits the binding of histamine on H2 receptors located on gastric parietal cell, thereby preventing acid secretion into the stomach lumen. It also inhibits gastric acid secretion induced by gastrin.

10 THERAPEUTIC USES Peptic ulcers Acute Stress ulcer GERD 10

11 11 Side effects : Headache, diarrhea, Mental confusion, muscular pain, dizziness ( ALSO GYNACOMASTIA,GALACTORRHEA and REDUCED SPERM COUNT WITH CIMETIDINE)

12 Drug interaction: ↓ absorption of drugs that require acidic medium for absorption e.g., ketoconazole, vit B12 Cimetidine is a P450 inhibitor and ↑es activity of drugs that are metabolized via P450 12

13 13 PROTON-PUMP INHIBITORS OMEPRAZOLE LANSOPRAZOLE PANTOPRAZOLE ESMOPRAZOLE RAMIPRAZOLE SIDE EFFECTS: ACHLORHYDRIA GASTRITIS

14 14 Action Blocks the H ⁺/K⁺ ATPase pump, thereby preventing the secretion of H ⁺ for K⁺ into the stomach lumen.

15 15 USES Erosive esophagitis Peptic ulcer GERD Gastric acid hypersecretory states, including Zollinger -Ellison syndrome

16 16 PROSTAGLANDINS MISOPROSTOL(PGE1) These inhibit the secretion of Hcl by stimulate production of mucus and bicarbonate ( Cytoprotective effect). Only used for NSAID induced ulcers. Not used commonly for others. CI: DURING PREGNANCY

17 17 ANTIMUSCARINIC DRUGS Dicylomine Propantheline Pirenzepine Hyoscyamine Mepenzolate

18 18 Muscarinic receptor stimulation increases secretory activity. Mech of Action: prevents gastric acid secretion. Not as effective as H2 receptor blockers Uses: Zollinger – Ellison Syndrome Peptic ulcer disease

19 19 SE Dryness of mouth Blurred vision Urinary retention Cardiac arrhythmias

20 20 MUCOSAL PROTECTIVES SUCRALFATE COLLOID BISMUTH SALTS Prevents mucosal injury, reduce inflammation and heal existing ulcers.

21 21 SUCRALFATE Mech Of Action: Complex of polyaluminum hydroxide and sulfated sucrose sulfate which binds proteins in normal and ulcerated mucosa forming a gel that acts as a physical barrier that impairs diffusion of HCl and degradation of mucus by acid and pepsin. USES: Duodenal ulcer

22 22 COLLOID BISMUTH SALTS May inhibit pepsin activity Increase secretion of mucus Forms a gel that coats and protects the ulcer crater by preventing the diffusion of acid.

23 23 ANTACIDS DRUGS Al(OH)3 Mg (OH )2 NaHCO3 COMMON SIDE EFFECT – MAY AFFECT ABSORPTION OF MANY OTHER DRUGS Azoles, floroquinolones, tetracyclines, warfarin, quinidine SIDE EFFECT CONSTIPATION DIARRHOEA SYSTEMIC ALKALOSIS, belching & flatulence

24 24 Anti-Emesis Drugs Why do we vomit?! Stimulation of the “Vomiting Centers”, “chemoreceptor trigger zone” and vestibular system (which functions mainly in motion sickness).

25 25 EMESIS/VOMITING RECEPTORS INVOLVED DOPAMINE – DA2 SEROTONIN- 5 HT3 Histamine- H1-receptor via the vestibular system Muscarinic: via the vestibular system

26 26 Anti-emetic MEDICATIONS used for chemotherapy induced emesis DOPAMINE ANTAGONISTS- Prochlorperazine, Metoclopramide, Haloperidol CANABINOIDS: DRONABINOL CORTICOSTEROIDS – Dexamethasone 5-HT3 ANTAGONISTS ONDANSETRON GRANISETRON

27 Antiemetic agents for motion sickness Anti histamines: diphenhydramine, dimenhydrinate, meclizine Anti muscarinic: Works via blockade of the vestibular system which gives afferent input to the vomiting center e.g., scopolamine 27

28 28 **ONDANSETRON** POWERFUL CENTRAL ACTING ANTIEMETIC COSTLY CONTROLS VOMITING POSTOP AND IN PT’S UNDERGOING CANCER CHEM.. SE; HEADACHE DIARRHEA

29 29 Diarrhea - Three Mechanisms Osmotic – osmoticant in intestine Secretory – excessive mucosal secretion – toxins, Infections Inflammatory H2OH2O

30 30 Lactase Deficiency … One Cause of Diarrhea Deficiency of lactase at brush border Presents as bloating, crampy pain, osmotic diarrhea Microvillus Enzymes

31 31 Antidiarrheals Antimotility Agents – Diphenoxylate, Loperamide Both are meperidine derivatives Activate presynaptic opioid receptors, inhibit Ach release → ↓ peristalsis Adsorbents: by adsorping intestinal toxins – Kaolin, pectin Agents that modify fluid/electrolyte transport – NSAIDS ( Inhibit prostaglandins) – Bismuth subsalicylate (Pepto Bismol)

32 32 Bismuth subsalicylate (Pepto Bismol) Decreases fluid secretion in the bowel. Used for Traveler’s Diarrhea

33 33 Constipation Many Causes – Neurogenic eg: Hirschsprung’s – Muscle weakness eg: post-surgery – Low-residue diets

34 34 LAXATIVES A. Irritants and Stimulants – Castor oil, aloe, Bisacodyl Castor oil broken down into ricinoleic acid (irritant) – B. Bulking Agents: – Psyllium, bran, lactulose magnesium (form gels) C. Stool softeners – Ducosate sodium, mineral oil, glycerin suppositories,. H20H20


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