Pharmacology

Peptic Ulcer Disease Imbalance between mucosal defensive

factors and aggressive factors Major defensive – mucus and bicarbonate Major aggressive – gastric acid, H. pylori,

nonsteroidal anti-inflammatory drugs, pepsin

Defensive factors Prevent the stomach and duodenum from being

harmed (self-digestion). Mucus – continually secreted, protective effect Bicarb – secreted from endothelial cells, neutralized

hydrogen ions Blood flow – good blood flow helps to maintain

mucosal integrity Prostaglandins – stimulate secretion of bicarb and

mucus and help promote blood flow, suppress secretion of gastric acid

Aggressive factors Helicobacter pylori – gram negative

bacteria, can live in stomach and duodenum

May breakdown mucus layer, inflammatory response to presence of the bacteria may breakdown defenses, also produces urease – forms CO2 and ammonia which are toxic to mucosa

NSAIDS – inhibit the production of prostaglandins

Decrease blood flow, decrease mucus production and bicarb synthesis, promote gastric acid secretion

Gastric Acid – also needs to be present for ulcer to form – activates pepsin and injures mucosa

Pepsin Smoking

Classes of drugs Antibiotics Antisecretory agents Mucosal protectants Antisecretory agents that enhance mucosal

defenses Antacids

Nondrug therapy Diet – change in eating pattern, 5-6 small

meals a day Smoking cessation, NSAID and ASA

should be avoided whenever possible, avoid alcohol

Antibacterial drugs Combinations must be used Bismuth – disrupts cell wall of H. pylori,

pepto-bismol Clarithromycin – inhibits protein synthesis Amoxicillin – disrupts cell wall, good

when given with omeprazole Tetracyclin – inhibits protein synthesis Metronidazole – resistance,

Histamine 2-receptor antagonists Suppress secretion of gastric acid (activation of

H2 receptors promotes secretion of gastric acid) Cimetidine - first available, oral, IV, IM May take up to twelve weeks for ulcer to be

healed Therapeutic uses – ulcers, GERD, Zollinger-

ellison syndrome, aspiration pneumonitis, heartburn, indigestion

Ranitidine (Zantac) More potent – than cimetidine Fewer side effects Fewer drug interactions PO, IM, IV Famotidine, Nizatidine

Proton Pump Inhibitors Suppress secretion of gastric acid Omeprazole – prilosec – prodrug that

converts to active form in parietal cells of stomach – inhibits enzyme that generates gastric acid

Ulcers, GERD, Zollinger-Ellison syndrome May contribute to development of gastric

tumors?

Other PPIs Lansoprazole Rabeprazole Pantoprazole – protonix – usually given 40

mg per day

Sucralfate Creates a protective barrier against acid

and pepsin Form sticky gel that coats ulcer portion Given every 6 hours Very few side effects – minimal systemic

absorption

misoprostol Cytotec – prevention of gastric ulcers

caused by long-term NSAID therapy Replacement for endogenous

prostaglandins

Antacids Peptic ulcers and GERD Neutralize acid Dosing – 7 times per day

Laxatives Laxative effect – production of a soft

formed stool over a period of 1 or more days

Catharsis – prompt, fluid evacuation of the bowel, more intense

Function of the colon – water and electrolyte absorption

Bowel evacuation – individual

Dietary fiber

Constipation Consistency vs. frequency Causes – diet and fluid, medications,

activity

Indications for laxative use Pain associated with bowel movements To decrease amount of strain under certain

conditions Evacuate bowel prior to procedures or

examinations Remove poisons To relieve constipation caused by

pregnancy or drugs

Laxative contraindications Inflammatory bowel diseases Acute surgical abdomen Chronic use and abuse

Classifications I – osmotic (high doses) II – osmotic (low doses), stimulant except

castor oil – most frequently abused III – bulk-forming, surfactant

Bulk-forming Identical to fiber – soften fecal mass,

increasing bulk Temporary treatment of constipation,

preferred for patients with inflammatory bowel diseases

May help with diarrhea

Adverse reactions Not absorbed – no systemic effects Must take with sufficient water Intestinal, esophageal obstruction Metamucil, citrucel

Surfactant laxatives Bisacodyl, castor oil Stimulate intestinal motility Increase water and electrolytes in intestinal

lumen Produce stool within 6-12 hours

types Bisacodyl – dulcolax – suppository, orally Anthraquinones – cascara and senna Castor oil – works in small intestine

Osmotic laxatives Draws water into intestinal lumen Time of action is dose-dependent Magnesium, sodium and potassium salts Can cause dehydration Electrolyte imbalances

Miscellaneous laxatives Mineral oil Lactulose Glycerin suppository Polyethylene glycol-electrolyte solutions

Laxative abuse Most common cause of constipation Teaching

Prokinetic agents Reglan – suppresses emesis and increases

upper GI motility Given for nausea related to chemotherapy GERD Diabetic gastroparesis Adverse effects – diarrhea, sedation, EPS,

(dopamine antagonist)

propulsid GERD and nocturnal heartburn Taken off the market Causes potentially lethal dysrhythmias

Antiemetic drugs Serotonin receptor antagonists –

Ondansetron (Zofran) – most effective with chemo-type drugs, very effective – works well with dexamethasone

Phenothiazines Blocks dopamine2 receptors in the

chemoreceptor trigger zone Side effects include EPS, anticholinergic

effects, hypotension and sedation Prochlorperzine, phenergan,

butyrophenones Haloperidol and droperidol (Inapsine) Block dopamine 2 receptors in

chemoreceptor trigger zone

Additional drugs Glucocorticoids Cannaboids Benzodiazepines Antihistamines

Antidiarrheals Symptom – excessive volume and fluidity

of stools Infection, digestion problems, bowel

disorder, inflammation

Complication and goal of treatment Electrolyte imbalances and dehydration Goal of treatment – treat underlying cause,

replace water and salts (electrolytes), relief of pain, cramping and reducing passage of unformed stools

Nonspecific – treat symptoms Opioids – slow intestinal motility, decrease

fluid in small intestine – stool goes into large intestine with less fluid

Lomotil and imodium Bulk-forming agents Anticholinergics antispasmodics - atropine

Infectious diarrhea Infections – bacteria and virus Salmonella, shigella, campylobacter,

clostridium Traveler’s diarrhea – e coli

Crohn’s disease and ulcerative colitis Aminosalicylates – sulfasalazine –

metabolized producing component which reduces inflammation

Mild to moderate ulcerative colitis

Glucocorticoids – suppress inflammation Primarily used for an exacerbation

immunomodulators Azathioprine and mercaptopurine Cyclosporine Infliximab methotrexate

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