Drugs for the Digestive System

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Drugs for the Digestive System

• Chapter 26

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Digestive System

• May be divided into alimentary canal/gastrointesti
  nal tract (mouth to anus) and accessory organs
  (liver, gallbladder, pancreas)
• GI tract- responsible for transportation of food
  as well as production of enzymes for breakdown of
  food into small molecules for absorption
• Peristalsis- movement of food through tract
  through contraction of smooth muscle
• Too fast- ? absorption of nutrients and water
  (diarrhea)
• Too slow- constipation

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Peptic Ulcer Disease

• Defined as an erosion of mucosa of stomach or
  duodenum
• Parietal cells in mucosa secrete hydrochloric
  acid to break down food and kill microbes
• Other cells secrete bicarbonate to neutralize the
  acid
• Many risk factors for development of PUD
• Most ulcers are caused by Helicobacter pylori
  infection ( blood test or biopsy of the ulcer
  will confirm)
• NSAIDS are second most common cause, ETOH is also
  a factor
• Whatever the cause, there is either an ? in acid
  or ?in protective mucus and/or bicarbonate
• Sx gnawing or burning pain on empty stomach
  which is sometimes relieved by food anorexia,
  weight loss, vomiting (occ. with blood), black
  tarry stools

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Gastroesophageal Reflux Disease(GERD)

• Acidic stomach contents move up into the
  esophagus, causing heartburn and possibly
  esophageal erosion
• Usually related to loosening of lower esophageal
  sphincter (LES), the ring of muscle at the bottom
  of the esophagus
• Triggers tobacco, ETOH, mint, caffeine,
  chocolate, carbonation, acidic foods, lying down
  after eating, too much fluids consumed with food
• Treatment is often the same as treatment for PUD

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PUD treatment

• Eliminate tobacco and ETOH
• ? stress
• Histamine-2 receptor antagonists
• Antibiotics
• Proton pump inhibitors
• Antacids
• Miscellaneous agents

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Histamine-2 Receptor Antagonists (ranitidine)

• H-1 receptors- located in vessels, bronchi
  stimulation results in inflammatory response
• H-2 receptors- located in stomach stimulation
  results in acid secretion
• Ranitidine blocks the H-2 receptor, ? volume of
  acid secretion
• Also useful for GERD
• SE bone marrow suppression (rare)

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Proton Pump Inhibitors (omeprazole)

• Inhibits the pump in parietal cells that secretes
  acid, or protons
• More effective at ? acid secretion than H-2
  blockers, but more expensive and onset of relief
  is slower
• SE nausea, diarrhea, abdominal pain

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Antacids (various)

• Oldest treatment for PUD and GERD, but not as
  effective
• These are bases that neutralize acid
• Simethicone may be added to ? gas bubbles
• Many are appropriate as a calcium supplement
• SE few may cause constipation or interfere with
  absorption of other medications

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Antibiotics for PUD

• Amoxacillin, clarithromycin, metronidazole, and
  tetracycline are all effective at eradicating H.
  pylori
• 2 or more abx are usually given to ? likelihood
  of bacterial resistance

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Miscellaneous Agents for PUD

• Sucralfate- coats ulcer
• Misoprostal- prostaglandin-like substance that
  increases production of stomach mucus
• Pregnancy Category X, can even be used to
  terminate pregnancy

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Constipation

• Defined as difficult to pass or infrequent bowel
  movements, may be related to a variety of factors
• Occasional constipation doesnt necessarily
  warrant medication
• For chronic constipation, consider mild exercise
  and dietary changes before medication
• Remember that clients can become dependant on
  anything that helps stimulate bowel movement

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Laxatives (psyllium)

• Colon is responsible for absorbing water from
  stool
• These drugs decrease the colons absorption of
  water
• Laxatives promote defecation through different
  mechanisms
• Bulk forming (psyllium)- absorb water into stool
• Stimulants- increase peristalsis
• Stool softeners-bring more water into stool
• Miscellaneous- usually oils taken rectally or
  orally to soften
• Cathartics- promote complete evacuation of the
  bowel

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Diarrhea

• Not enough water is reabsorbed from stool
• Occasional diarrhea doesnt warrant treatment
  other than something mild OTC, as the body may be
  trying to eliminate an infectious agent
• Extended bouts can lead to dehydration and change
  in electrolytes

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Antidiarrheals (diphenoxylate with atropine)

• Opioids are most effective
• Addition of atropine discourages clients from
  taking too much of the opioid
• Bismuth products (Pepto-Bismol) are less
  effective but perhaps safer
• These drugs slow peristalsis in colon, allowing
  more water to be absorbed by colon
• SE constipation, bowel obstruction (rare, but
  more common in elderly)

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Nausea and Vomiting/Emesis

• Numerous causes, such as pregnancy,
  antineoplastics, infection, head trauma, pain,
  motion sickness, etc.
• Emesis can lead to electrolyte imbalance

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Antiemetics (prochlorperazine)

• Many can be given by injection or suppository as
  well as orally
• More effective if used in advance
• SE drowsiness (common), constipation and
  increased heart rate (less common)

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Anorexiants (sibutramine)

• Reduce appetite to assist in weight loss
• Usually act as stimulants, promoting loss of
  about 10 of initial body weight over a year
• Tolerance is common
• Cessation usually results in return of weight
  (and possibly more)
• SE insomnia, ? heart rate, ? blood pressure
  (avoid in cardiac patients)