Pharmacology Session 4:

This note group is focused on the GI system, and is basically a list of drugs without any concepts. We covered laxatives, antidiarrheals, mouthwashes, and stomach acid lowering agents. Good luck!

-Peter

GI drugs  

Session 4

This is the beginning of test 2 material

Drugs that affect the mouth

Basic types:

  • Mouthwashes
    • alcohol
      • This may be painful for patients with stomatitis
      • alcoholics
    • Hydrogen peroxide releases O2
    • fluoridated
    • antiseptic – Phenol
  • Dentifrice is abrasive

Pts with gum Dx or that are having major dental work done will put the patients at High risk for MI

Hyperacidity

  • Antacids that can be bought over the counter (the goal is to bring pH of the stomach to about 3.5): Tums, Caltrate, OsCal, Viactiv(not w/ coumadin), Citracal (not w/ KD)
    • Action: increase stomach pH
    • indications: Peptic ulcer, GERD, hernia
    • ADME:
      • onset: 20-40 min (give 1-3hr before meal + night)
      • not meant to absorb, just buffer the acid
      • excreted in the feces
    • reduces Absorption of other drugs (chelation) due to the raise in stomach pH
    • S/E: constipation, bone deg, increased acid secretion, Kidney failure, Diarrhea
      • increased Ca, K and NA, decreased Mg
      • Kidney failure in chronic use

Digestants and enzymes

  • pancrelipase (Pancreaze )
    • ind: Pancreas insufficiency (pancreatitis, cystic fibrosis, Pancreatectomy)
    • Act: increased digestion in GI (enzymatic)
    • Enteric coated
    • S/E all abdominal, Fibrosing
    • hold if NPO, give before meals (dose based on calories)

Antiemetics

  • Action: Block CTZ (chemoreceptor trigger zone)
    • relieve nausea and vomiting
  • Anticholinergic: Scopolamine (Transderm-Scop)
    • for motion sickness
    • Side effects: Blurred vision, dry mouth and CNS depression
  • Antihistamines
    • Diphenhydramine (Benadryl)
    • Dimenhydrinate (Dramamine)
      • H1 blocker (antihistamine), CNS depression
  • Phenothiazine:
    • Prochlorperazine (compazine)
      • similar to atropine
  • Dopamine receptor blocker
    • Metoclopramide (Reglan)
      • Drousie, extrapyramidal effects, Diarrhea
  • Cannabinoid
    • Dronabinol (Marinol)
      • Made from THC
  • Bismuth Salts
    • Bismuth subsalicylate (Pepto-Bismol)
      • OTC, constipation, grey stool, ASA

Ondansetron (Zofran)

  • Block serotonin 5 HT3 receptors

Peptic ulcer Drugs

  • Acid-Neutralizing Drugs
  • H2 receptor blocker
    • Cimetidine (tagamet)
    • ranitidine (Zantac) fewer side effects and strogerew
      • Better value to prevent ulcer than PPI
      • Action: Lowers H2 secretion by stopping histamine from stimulating H2 receptors
      • Prevents PUD, acid reflux, hypersecretion
  • Cytoprotective agents (IMP)
    • Sucralfate (Carafate, Sucralfate)
      • Protects ulcer by forming a barrier with the ulcer cells from acid in the stomach.
      • For PUD, and protect other ulcers from forming. (NSAID’s)
    • Misoprostol (cytotec)
      • PG E1 analog – ↓Acid secretion, ↑ Bicarb (HCO3) and mucus secretion
      • Category X
      • Prevents NSAID ulcers
  • Proton Pump inhibitors, PPI
    • omeprazole (Prilosec) -prazole
      • better at repairing ulcers than H2 blocker
      • Blocks acid secretion
        • Blocks ATPase at the parietal cells that would produce H2
        • treats: esophagitis from GERD, Duodenal ulcer, long term HTN
        • quick onset, 2h to peak, and ends effectiveness at 3-4 days
        • Side effects are: Heartburn, weakness, dizziness, C.diff risk increases, also cannot absorb Ca as efficiently
      • Ulcers can heal in a matter of weeks
  • Treatment plan for Peptic ulcer disease from H. pylori
    • Antibiotics, Bismuth, PPI
    • lasts for 2, and then the Antibiotics and bismuth drop off and the PPI is prescribed for 4 more weeks, about 90% of people are recovered after this treatment.

Laxatives

  • do other interventions before meds, such as diet and exercise
  • Bulk forming laxatives
    • psyllium (metamucil)
      • encreases stool size and softens by absorbing water, this increases the size of the bolus and pushes against the wall of the intestine to stimulate peristalsis
      • takes 12hr -3 days work
      • excreted in stool
      • NEED fluid for it to work!
  • Surfactant Laxatives (stool softeners)
    • Docusate sodium (Colace)
      • ↓ Surface tension softening the stool
      • 12hr- 3 days to work
      • does not interfere with absorption of nutrients
  • Stimulant Laxatives
    • bisacodyl (Dulcolax)
      • stimulate peristalsis by affecting the muscle and mucus secreting cells
      • works in 6-8hr
      • can cause fluid loss (watery discharge), cramping, and dependence
  • Osmotic Laxatives
    • lactulose and milk of magnesia
      • sugar, and salt that don’t absorb well and then attract water to induce peristalsis.
      • ↓serum Ammonia in people with chronic liver disease
      • works in 1-3 days and not much is absorbed into the body
    • polyethylene glycol (Golytely) (Glycerin sup in children)
      • draws water into intestine (sugar, salt, and PEG)
      • Cleansing before colonoscopy
      • (Other) metoclopramide (Reglan)
    • ↑ ACH, stim PSNS
    • ↑secretions, and motility
    • for GERD, risk of ileus, and to eliminate barium
    • Contra indicated in patient with intestinal blockage
  • Motion sickness
    • scopolamine
      • Muscarinic antagonist
      • blocks inner ear from vomiting center
        • H1, and cholinergic are blocked
      • PO, subQ, transdermal
      • similar action on motion sickness are antihistamines like meclizine (Antivert) and dimenhydrinate (Dramamine)

Antidiarrheals

  • concerned about fluid and electrolyte loss
    • Tachycardia, orthostatic hypotension, ↑ Hct, BUN
    • watch for dependance
  • Opioids
    • tincture of opium, paregoric
      • reabsorption of water out of the intestines and reduces pn, spasms
      • for persistent diarrhea, but not when caused by foreign organism
      • dose q 4-6hr
      • these are scheduled drugs, can be addictive
  • Synthetic Opioid
    • loperamide (imodium), diphenoxylate and atropine (Lomotil)
      • same action and effect as opioids
      • 5hr peak, 24 hr duration
      • side effects rash, agitation, and other low fluid S/E
      • Absorbents
        • cholestyramine (Questran)
          • attracted to acids, and bind to irritants
          • used in hypercholesterolemia
          • constipation is a side effects

antibiotic- induced Diarrhea for the elimination of C. diff with the antibiotic fidaxomicin (Dificid)

  • give probiotics to bring back normal flora

Obesity Drug

  • phentermine and toprate (QNexa)
    • taken off market Dt pulmonary HTN and heart valve problems
      • 10% weight loss
  • Orlistat (Xenical – Rx or Alli – OTC)
    • blocks fat absorption by blocking lipase
    • OTC
    • fatty stool, ↓ FS vitamins + beta-carotene
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