W14 Drugs acting on GIT.pptx

Summary of drugs acting on GIT ‫كليــة الصيدلة‬ Treatment of peptic ulcer disease (PUD) ‫كليــة الصيدلة‬  Pharmacological treatment of PUD A- Treatment of H. pylori:  Using different combinations of antibacterial drugs...

Summary of drugs acting on GIT ‫كليــة الصيدلة‬ Treatment of peptic ulcer disease (PUD) ‫كليــة الصيدلة‬  Pharmacological treatment of PUD A- Treatment of H. pylori:  Using different combinations of antibacterial drugs B- Suppression of acid secretion:  Histamine H2-antagonists  Proton pump inhibitors (PPIs)  Antacids C- Protective agents  Sucralfate  Misopristol  Bismuth (These agents form a protective barrier on epithelial cells. They prevent mucosal injury, reduce inflammation and  Eradication of H. pylori  Approximately 90% of patients with duodenal ulcer are infected with H. pylori and peptic ulcer is more likely to develop in patients with gastritis who are H. pylori positive  H. pylori is diagnosed by endoscopy, serological and urea breath test Treatment (10-14 days):  First line: Clarithromycin triple OR Bismuth quadruple  Second line: Levofloxacin triple  Third line: Rifaputin triple  Choice of regimen depends on previous treatment with clarithromycin, penicillin sensitivity, cost and adverse effects.  Eradication of H. pylori  Histamine H2-antagonists  Ex: Cimetidine, Ranitidine  Oral and IV  They inhibit the parietal cell H2 receptor (NO effect on H1) and are especially effective at inhibiting nocturnal acid secretion (which depends largely on histamine).  They have a modest impact on meal-stimulated acid secretion (which is stimulated by gastrin and acetylcholine as well as histamine)  They inhibit 60–70% of total 24-hour acid secretion  Largely replaced by proton pump inhibitors (PPIs)  Effective in GERD, uncomplicated PUD (treatment for 6-8 weeks, PPIs are preferred if H. pylori or NSAIDs-induced), non-ulcer dyspepsia and prevention of bleeding from stress-related gastritis (IV).  Proton pump inhibitors (PPIs) Ex: Omeprazole, and Pantoprazole  Prodrugs (activated in stomach) that irreversibly inhibit H+/K+- ATPase (the last step of forming HCl). The enzyme needs 18 hrs to be resynthesized, therefore they have long duration effect.  In contrast to H2 antagonists, PPIs inhibit both fasting and meal-stimulated secretion (by 90-98%) and therefore PPIs are superior to H2 antagonists in suppressing acid and healing PUD Clinical use:  GERD,  PUD either H. pylori or NSAIDs-induced,  Gastrinoma and other hypersecretory conditions  Prevention of rebleeding from peptic ulcers, and  Antacids  Chemically neutralize HCl  They can be non-systemic (form non-absorbed salts with HCl) or systemic (only Sodium bicarbonate that is soluble and can be absorbed (but may cause alkalosis)  Rapid onset (bicarbonate is the fastest), but short duration (up to 2 hours)  Useful in dyspepsia and symptomatic relief in GERD and peptic ulcer.  Can interact with several drugs (Ex. Tetracyclines, iron, fluoroquinolones, digoxin, phenytoin, chlorpromazine, isoniazid,….)  Carbonates can cause flatulence and bloating due to CO2 released  Antacids Drugs for diarrhea ‫كليــة الصيدلة‬   Approaches to treatment of diarrhea There are three approaches to the treatment of severe acute diarrhoea: 1. Maintenance of fluid and electrolyte balance 2. Use of anti-infective agents (Azithromycin or ciprofloxacin for bacteria), Antiprotozoal (Metronidazole for giardia and amoeba) 3. Use of antimotility or other antidiarrhoeal agents such as astringents, protective and adsorbents,....  Antimotility agents Ex. Loperamide  Activates presynaptic opioid receptors in the enteric nervous system, thus inhibit acetylcholine release and decrease peristalsis (Do not cross the BBB).  Side effects: Drowsiness, Abdominal cramps, Dizziness, constipation.  Toxic megacolon, they should not be used in young children (