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PHARMACOLOGY - PowerPoint

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									        PHARMACOLOGY
• Gastrointestinal drugs
             OBJECTIVES
• Identify classes of drugs used to improve GI
  function.
• Identity uses and varying actions of these
  drugs.
• Identify how these drugs are absorbed,
  distributed, metabolized, and excreted.
• Identify drug interactions and adverse
  reactions to these drugs.
DRUGS AND THE GI SYSTEM
• Classes of drugs used to improve GI
  function include:
• Peptic ulcer drugs
• Adsorbent, antiflatulent, and digestive drugs
• Antidiarrheal and laxative drugs
• Antiemetic and emetic drugs
     PEPTIC ULCER DRUGS
• Aimed at either eradicating H. pylori or
  restoring balance between acid and pepsin
  secretions and the GI mucosal defense.
• These drugs include: systemic antibiotics,
  antacids, Histamine-2 (H2)-receptor
  antagonists, proton pump inhibitors, and
  other peptic drugs such as misoprostol and
  sucralfate.
   SYSTEMIC ANTIBIOTICS
• Treatment of peptic ulcers caused by H.
  pylori include the use of at least two
  antimicrobial drugs and an antacid for two
  weeks.
• Systemic antibiotics used to treat H. pylori
  include: metronidazole, tetracycline,
  clarithromycin, and amoxicillin.
   SYSTEMIC ANTIBIOTICS
• Pharmacokinetics:
• Vary in absorption; tetracycline’s
  absorption is decreased when taken with
  dairy products; distributed widely; excreted
  primarily in the urine.
• Pharmacodynamics:
• Act by treating the infection.
   SYSTEMIC ANTIBIOTICS
• Pharmacotherapeutics:
• Combined with either an H2-receptor
  antagonist or a proton pump inhibitor to
  decrease stomach acid and promote healing.
• Drug interactions:
• Tetracycline increases digoxin levels and
  the risk of bleeding when taken with oral
  anticoagulants.
   SYSTEMIC ANTIBIOTICS
• Adverse reactions:
• GI disturbances
              ANTACIDS
• Over-the-counter medications that include:
• Magnesium hydroxide and aluminum
  hydroxide
• Simethicone
• Magaldrate
• Calcium carbonate
              ANTACIDS
• Pharmacokinetics:
• Work locally in the stomach by neutralizing
  gastric acid.
• Distributed throughout the GI tract;
  eliminated primarily in the feces.
• Pharmacodynamics:
• Reduces the total amount of acid in the GI
  tract.
             ANTACIDS
• Pharmacotherapeutics:
• Prescribed to relieve pain and promote
  healing in peptic ulcer disease.
• Also used to relieve symptoms of acid
  indigestion, heart-burn, dyspepsia, or
  GERD.
• Also used to prevent stress ulcers, GI
  bleeding, and hyperphosphatemia in kidney
  failure.
              ANTACIDS
• Drug interactions:
• All antacids can interfere with the
  absorption of oral drugs given at the same
  time.
• Adverse reactions:
• Diarrhea, constipation, electrolyte
  imbalances
          H2-RECEPTOR
          ANTAGONISTS
• Commonly prescribed anti-ulcer drugs
  include:
• Cimetidine (Tagamet)
• Nizatidine (Axid)
• Ranitidine (Zantac)
• Famotidine (Pepcid)
           H2-RECEPTOR
           ANTAGONISTS
• Pharmacokinetics:
• Absorbed rapidly and completely except for
  famotidine; food and antiacids may reduce
  absorption; distributed widely throughout
  the body; metabolized by the liver; excreted
  primarily in the urine.
• Pharmacodynamics:
• Block histamine from stimulating the acid-
  secreting parietal cells of the stomach.
           H2-RECEPTOR
           ANTAGONISTS
• Pharmacotherapeutics:
• Used therapeutically to:
• Promote healing of duodenal and gastric
  ulcers.
• Provide long-term treatment of pathological
  GI hypersecretory conditions.
• Reduce gastric acid production and prevent
  stress ulcers.
           H2-RECEPTOR
           ANTAGONISTS
• Drug interactions:
• Cimetidine inhibits metabolism of ethyl
  alcohol in the stomach resulting in higher
  blood alcohol levels.
• Adverse reactions:
• Headache, diarrhea, and rash
 PROTON PUMP INHIBITORS
• Disrupt chemical binding in stomach cells
  to reduce acid production, lessening
  irritation and allowing peptic ulcers to heal.
• These drugs include:
• Rabeprazole (Aciphex)
• Pantoprazole (Protonix)
• Omenprazole (Prilosec)
• Lansoprazole (Previcid)
 PROTON PUMP INHIBITORS
• Pharmacokinetics:
• Given orally in enteric-coated form to
  bypass the stomach and are dissolved and
  absorbed in the small intestine.
• Highly protein-bound and are extensively
  metabolized by the liver; eliminated in the
  urine.
 PROTON PUMP INHIBITORS
• Pharmacodynamics:
• Block the last step in the secretion of gastric
  acid by combining with hydrogen,
  potassium, and adenosine triphosphate in
  the parietal cells of the stomach.
    PROTON PUMP INHIBITORS
• Pharmacotherapeutics:
• Indicated for:
• Short term treatment of gastric ulcers
• Active duodenal ulcers and peptic ulcers (H.
  pylori)
• Erosive esophagitis
• GERD
• Hypersecretory states
 PROTON PUMP INHIBITORS
• Drug interactions:
• May interfere with the metabolism of
  diazepam, phenytoin, and warfarin.
• May also interfere with drugs that depend
  on gastric pH for absorption.
• Adverse reactions:
• Abdominal pain, diarrhea, nausea, and
  vomiting
     OTHER PEPTIC ULCER
           DRUGS
• Misoprostol (Cytotec) - Protects against
  peptic ulcers caused by NSAIDs by
  reducing the secretion of gastric acid and by
  boosting the production of gastric mucus.
• Sucralfate (Carafate) - Works locally in the
  stomach by rapidly reacting with
  hydrochloric acid to form a thick, paste-like
  substance that adheres to the gastric
  mucosa.
      ADSORBENT DRUGS
• Prescribed as antidotes for the ingestion of
  toxins which are substances that can lead to
  poisoning or overdose.
• Most commonly used adsorbent drug is
  activated charcoal.
• Pharmacokinetics:
• Must be given soon after toxic ingestion;
  not absorbed or metabolized; excreted
  unchanged in feces.
      ADSORBENT DRUGS
• Pharmacodynamics:
• Inhibits toxins from being absorbed in the
  GI tract by attracting and binding with
  them.
• Pharmacotherapeutics:
• A general purpose antidote used for many
  types of acute oral poisoning.
      ADSORBENT DRUGS
• Drug interactions:
• Drugs to induce vomiting that had been
  given before administration, now are
  discouraged so administration is not
  delayed.
• Adverse reactions:
• Black stools and constipation.
  ANTIFLATULANT DRUGS
• Disperse gas pockets in the GI tract.
• Simethicone is the major drug currently
  used.
• Pharmacokinetics:
• Not absorbed in the GI tract; distributed to
  the intestinal lumen; eliminated in the feces.
    ANTIFLATULANT DRUGS
•   Pharmacodynamics:
•   Provide de-foaming action in the GI tract.
•   Pharmacotherapeutics:
•   Used to treat conditions in which excess gas
    is a problem such as: functional gastric
    bloating, postop gaseous bloating,
    diverticular disease, spastic or irritable
    colon, and air swallowing.
  ANTIFLATULANT DRUGS
• Drug interactions:
• Don’t interact significantly with other
  drugs.
• Adverse reactions:
• None known.
       DIGESTIVE DRUGS
• Aid digestion in patients who are missing
  enzymes or other substances needed to
  digest food.
• Include:
• Dehydrocholic acid
• Pancreatin and pancrelipse.
        DIGESTIVE DRUGS
• Pharmacokinetics:
• Aren’t absorbed; act locally in the GI tract;
  excreted in the feces.
• Pharmacodynamics:
• The action of digestants resembles the
  action of the body substances they replace.
• Dehydrocholic acid - bile
• Pancreatin and pancrelipase - pancreatic
  enzymes.
         DIGESTIVE DRUGS
•   These drugs contain:
•   Trypsin to digest proteins
•   Amylase to digest carbohydrates
•   Lipase to digest fats
       DIGESTIVE DRUGS
• Pharmacotherapeutics:
• Each digestant has its own indication:
• Dehydrocholic acid provides temporary
  relief of constipation.
• Pancreatic enzymes are given to patients
  with pancreatitis, cystic fibrosis, and
  steatorrhea.
        DIGESTIVE DRUGS
• Drug interactions:
• Antacids reduce the effects of pancreatic
  enzymes.
• Adverse reactions:
• Diarrhea
       ANTIDIARRHEAL &
       LAXATIVE DRUGS
• Antidiarrheals include: opioid-related drugs
  and kaolin and pectin.
• Laxatives include: hyperosmolar drugs,
  dietary fiber and related bulk-forming
  substances, emollients, stimulants, and
  lubricants.
    OPIOID-RELATED DRUGS
•   Decrease peristalsis in the intestines.
•   Include:
•   Difenoxin
•   Diphenoxylate (Lomotil)
•   Loperamide (Imodium)
  OPIOID-RELATED DRUGS
• Pharmacokinetics:
• Loperamide isn’t absorbed well; distributed
  in the serum; metabolized in the liver;
  excreted in the feces.
• Pharmacodynamics:
• Slow GI motility by depressing the circular
  and longitudinal muscle action in the small
  and large intestines.
  OPIOID-RELATED DRUGS
• Pharmacotherapeutics:
• Used to treat acute, nonspecific diarrhea.
• Loperamide is also used to treat chronic
  diarrhea.
• Drug interactions:
• May enhance the depressant effects of
  barbiturates, alcohol, narcotics,
  tranquilizers, and sedatives.
  OPIOID-RELATED DRUGS
• Adverse reactions:
• GI distress
        KAOLIN & PECTIN
• Locally acting OTC antidiarrheals that work
  by adsorbing irritants and soothing
  intestinal mucosa.
• Pharmacokinetics:
• Aren’t absorbed or distributed; excreted in
  the feces.
        KAOLIN & PECTIN
• Pharmacodynamics:
• Bind with bacteria, toxins, and other
  irritants on the intestinal mucosa.
• Pectin decreases the pH in the intestinal
  lumen which provides a soothing effect on
  the irritated mucosa.
• Pharmacotherapeutics:
• Used to relieve mild to moderate diarrhea.
        KAOLIN & PECTIN
• Drug interactions:
• Can interfere with the absorption of digoxin
  or other drugs from the intestinal mucosa if
  administered at the same time.
• Adverse reactions:
• Constipation
         HYPEROSMOLAR
           LAXATIVES
• Work by drawing water into the intestine
  promoting bowel distention and peristalsis.
• Include the following drugs:
• Glycerin
• Lactulose
• Saline compounds
         HYPEROSMOLAR
           LAXATIVES
• Pharmacokinetics:
• Glycerin is administered into the colon and
  isn’t absorbed systemically.
• Lactulose is administered orally; is
  minimally absorbed; distributed in the
  intestine; metabolized by bacteria in the
  colon; excreted in the feces.
         HYPEROSMOLAR
           LAXATIVES
• Saline compounds are administered orally
  and rectally; some ions are absorbed and
  excreted in the urine; the unabsorbed drug is
  excreted in the feces.
• Polyethylene glycol (PEG) or “GoLytely”
  act as an osmotic drug but is not absorbed
  so it doesn’t alter electrolyte balance.
         HYPEROSMOLAR
           LAXATIVES
• Pharmacodynamics:
• Produce a bowel movement by drawing
  water into the intestine.
• Pharmacotherapeutics:
• Glycerin is used in bowel retraining.
• Lactulose is used to treat constipation and
  decrease ammonia production and
  absorption from the intestines in liver
  disease.
         HYPEROSMOLAR
           LAXATIVES
• Saline compounds are used when prompt
  and complete bowel evacuation is required.
• Drug interactions:
• Don’t interact significantly with other drugs
  except for PEG.
• Adverse reactions:
• Electrolyte imbalances
DIETARY FIBER & RELATED
BULK-FORMING LAXATIVES
• A high fiber diet is the most natural way to
  prevent or treat constipation.
• Include the following drugs:
• Methylcellulose (Citrucel)
• Polycarbophil (Fiberall)
• Psyllium hydrophilic mucilloid (Metamucil)
DIETARY FIBER & RELATED
BULK-FORMING LAXATIVES
• Pharmacokinetics:
• Not absorbed systemically; polysaccharides
  in these drugs are converted into
  osmotically active metabolites that draw
  water into the colon; excreted in the feces.
• Pharmacodynamics:
• Increase stool mass and water content
  promoting peristalsis.
DIETARY FIBER & RELATED
BULK-FORMING LAXATIVES
• Pharmacotherapeutics:
• Used to:
• Treat simple constipation.
• Aid patients recovering from acute MI’s,
  cerebral aneurysms, or eye surgery who
  need to avoid the Valsalva maneuver.
• Manage patients with irritable bowel
  syndrome and diverticulosis.
DIETARY FIBER & RELATED
BULK-FORMING LAXATIVES
• Drug interactions:
• Decreased absorption of digoxin, warfarin,
  and salicylates if taken within two hours of
  these laxatives.
• Adverse reactions:
• Gas, distention, obstruction, impaction
  EMMOLIENT LAXATIVES
• Also known as stool softeners.
• Include the calcium, potassium, and sodium
  salts of docusate.
• Pharmacokinetics:
• Administered orally; absorbed and excreted
  through the bile in the feces.
   EMMOLIENT LAXATIVES
• Pharmacodynamics:
• Soften the stool and make bowel
  movements easier by allowing water and
  fats to penetrate the stool.
• Also stimulate electrolyte and fluid
  secretion from the intestinal mucosal cells.
  EMMOLIENT LAXATIVES
• Pharmacotherapeutics:
• The drug of choice for patients who should
  avoid straining during bowel movements
  including those with:
• Recent MI or cardiac surgery
• Disease of the anus or rectum
• Increased ICP
• Hernias
  EMMOLIENT LAXATIVES
• Drug interactions:
• May enhance the absorption of many oral
  drugs, therefore, drugs with a narrow
  therapeutic index should be administered
  cautiously.
• Adverse reactions:
• Seldom occur.
     STIMULANT LAXATIVES
•   Also known as irritant cathartics.
•   Include the following drugs:
•   Bisacodyl (Dulcolax)
•   Cascara sagrada
•   Castor oil
•   Phenolphthalein (Ex-Lax)
•   Senna (Senokot)
   STIMULANT LAXATIVES
• Pharmacokinetics:
• Minimally absorbed; metabolized in the
  liver; excreted in the urine and feces.
• Pharmacodynamics:
• Stimulate peristalsis and produce a bowel
  movement by irritating the intestinal
  mucosa or stimulating nerve endings of the
  intestinal smooth muscle.
   STIMULANT LAXATIVES
• Pharmacotherapeutics:
• The preferred drugs for emptying the bowel
  before general surgery, endoscopic
  procedures, and radiologic procedures.
• Also used to treat constipation caused by
  prolonged bedrest, neurologic dysfunction
  of the colon, and constipating drugs such as
  narcotics.
   STIMULANT LAXATIVES
• Drug interactions:
• Reduce the absorption of other oral drugs
  when administered at the same time.
• Adverse reactions:
• Weakness, nausea, abdominal cramps, mild
  rectal and anal inflammation.
   LUBRICANT LAXATIVES
• Mineral oil is the main lubricant laxative in
  current clinical use.
• Pharmacokinetics:
• Administered orally or rectally; minimally
  absorbed; distributed to the mesenteric
  lymph nodes, intestinal mucosa, liver, and
  spleen; metabolized by the liver; excreted in
  the feces.
   LUBRICANT LAXATIVES
• Pharmacodynamics:
• Lubricates the stool and the intestinal
  mucosa and prevents water reabsorption
  from the lumen of the bowel which
  increases peristalsis as well.
• Pharmacotherapeutics:
• Used to treat constipation and maintain soft
  stools when straining is contraindicated.
   LUBRICANT LAXATIVES
• Also used to treat patients with fecal
  impactions.
• Drug interactions:
• May impair the absorption of many oral
  medications such as fat-soluble vitamins,
  oral contraceptives, and anticoagulants.
• Adverse reactions:
• GI distress
       ANTIEMETIC DRUGS
• Derived from plants.
• Prevent vomiting.
• Include:
• Antihistamines - dimenhydrate (Dramamine),
  meclizine hydrochloride (Antivert)
• Phenothiazines - prochlorperazine (Compazine),
  promethazine hydrochloride (Phenergan)
      ANTIEMETIC DRUGS
• Serotonin receptor antagonists -
  ondansetron (Zofran) antiemetic of choice
  in the U.S., granisetron (Kytril)
• Pharmacokinetics:
• Absorbed well; metabolized by the liver;
  excreted in the urine and/or feces.
      ANTIEMETIC DRUGS
• Phenothiazines block the vomiting center in
  the medulla of the brain.
• Serotonin receptor antagonists block
  serotonin stimulation centrally in the
  chemoreceptor trigger zone and peripherally
  in the vagal nerve terminals, both of which
  stimulate vomiting.
      ANTIEMETIC DRUGS
• Pharmacotherapeutics:
• Antihistamines prevent or treat motion
  sickness.
• Phenothiazines and serotonin receptor
  antagonists control severe nausea and
  vomiting post-surgery, viral-related, during
  chemotherapy, and radiation therapy.
      ANTIEMETIC DRUGS
• Drug interactions:
• Many significant interactions and adverse
  reactions may occur, therefore, the nurse
  should always consult a drug handbook
  prior to administration.
           EMETIC DRUGS
• Used to induce vomiting in a person who
  has ingested toxic substances.
• Syrup of Ipecac is the drug of choice
  because it is the most effective and the least
  likely to cause problems.
• It has become controversial because it
  delays the use of charcoal.
            EMETIC DRUGS
•   Pharmacokinetics:
•   Little is known about its properties.
•   Vomiting occurs within 10 to 30 minutes.
•   Pharmacodynamics:
•   Induces vomiting by stimulating the
    vomiting center located in the medulla of
    the brain.
          EMETIC DRUGS
• Pharmacotherapeutics:
• Considered the therapy of choice for
  emptying the stomach because of its
  effectiveness and low incidence of adverse
  effects.
• Drug interactions: rarely occur.
• Adverse reactions: rarely produced.

								
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