GASTROINTESTINAL AGENTS
Objectives: Upon Completion the student will be able to:
- Identify causes of vomiting, diarrhea and constipation
- Explain the action and adverse effects of antiemetics, antidiarrheals, and laxatives.
- Identify predisposing factors for peptic ulcers.
- Describe the actions and adverse effects of anti-ulcer drugs.
- Describe prototypes of anticholinergics, histamine blockers, antacids, and proton pump inhibitors.
- Describe the nursing process with safe use of the above drugs.
Always look at the cause. If someone’s having acute abd pain, you have to figure out what the cause is before you admin meds to speed up or slow down pain. Never never admin meds before you’ve got a diagnosis.
Contraindications: undiagnosed abdominal pain, GI disorders
GI Tract
- Functions
- Digesting and absorption of nutrients: breakdown of food, absorption of water, electrolytes, nutrients; excretion.
- Components
- Oral Cavity • Esophagus
- Stomach • Sm. Intestine
- Lg. intestine • Anus
- Pathology
Vomiting
- causes: Bacterial/viral infection, motion sickness, pain, shock, food intolerance
- Vomiting: caused by—reactions to all meds, anesthesia, infections (viral or bacterial) food poisoning [also bacteria], drug toxicity, pregnancy and pain [like kidney stones], motion sickness, middle ear disturbance.
- Causative centers: CTZ [chemoreceptor trigger zone] and the “vomiting center” in the brain. These centers initiate the muscle contractions of the abs and diaphragm that squish the stomach contents out. Usually dopamine [or acetylcholine] activates the CTZ, which then triggers the
Non-drug remedies –
o drinking weak tea, flattened carbonated drinks, crackers, dry toast.
· Fluids are needed to restore fluids
Diarrhea: frequent liquid stool.
· Causes: Spicy food, fecal impaction, bacteria, toxins, drug rx, laxative abuse, over treatment of constipation, tube feedings mean liquid in and liquid out. Post op patients have a GI tract that’s just waking up from anesthesia. Dehydration, loss of electrolytes, and loss of a lot of alkaline pH are results. Perineal skin breaks down really quickly from poops and dirty bedding
· Can cause severe dehydration and electrolyte imbalance
Non-drug remedies –
o recommended until cause is known—don’t Rx without the cause identified.
o Clear liquids and oral solutions (Gatorade, pedialyte), IV electrolytes solutions.
Non drug interventions for vomiting, diarrhea: electrolytes, fluids, rest. Start with an easy liquid [clear liquid, ginger ale.] Some anti-emetic drug might be good, IV or SubQ would be better than
- Constipation – accumulation of hard fecal material in the lg. intestine.
o Causes – Water and diet are main problems. People that are inactive [like in the hosp] get constipated. People on opiate pain meds get constipated; we always treat with stool softeners. Diet matters too. Other drugs that cause slowing of gi tract. Chronic laxative use, paraplegia, lack of exercise, forgetting to poop. fecal impaction, bowel obst., chronic laxative use, Neuro disorders, lack of exercise, drugs (narcotic opiates are famous for this)
Non-drug remedies –
o diet that contains bulk/fiber, water, exercise, routine BM.
GERD: inflammation or erosion of the esophageal mucosa due to gastric reflux. Heartburn. Correlates with smoking and obesity. Treated like ulcers are: neutralize stomach acids, reduce acid secretion.
Peptic ulcers – broad term for ulcers found in the upper GI tract [stomach, duodenum, esophagus.] Occur when there is hypersecretion of HCl and from parietal cells.
Pre-disposing factors for ulcers:
1. Mechanical disturbances [hypersecretion]
2. Genetic influences [too many parietal cells]
3. Env. Influences [foods, TOB, stress, pregnancy, surg]
4. Heliobacter Pylori
5. Drugs [mostly pain/anti-inflam drugs: NSAIDS, aspirins, ibuprofen, corticosteroids, etc.]
Non-drug remedies – avoid tobacco, ETOH, avoid spicy, greasy foods, NSAIDs, Glucocortoids. Don’t eat before bed. HOB up.
Drugs for GI Tract Disorders
- Antiemetics - OTC
Actions – these prevent motion sickness and severe vomiting with cancer agents. They also inhibit vestibular stimulation of the middle ear, or coat the gastric mucosa.
Peptobismol/Bismuth Salts: coats the stomach. Diarrhea, gastric distress.
ANTIEMETICS: there’s lots of these, look at the general categories. Some decrease response in the brain that causes vomiting, but it also depresses other areas of the brain.
- Antihistamines
- Anticholinergics
- Dopamine antagonists
- Benzodiazepines
- Serotonin antagonists
- Glucocorticoids
- Cannabinoids
- Misc.
- Types of Prescription Antiemetics
· Antihistamines & Anticholinergics – These block dopamine receptors in the Chemoreceptor Trigger Zone (CTZ)
· Side effects & Adverse rxns: Dry mouth, blurred vison, tachycardia, constipation
o Antihistamines
o Diphenhydramine HCL (Benadryl) – Diphenhydramine works by blocking the effect of histamine at H1 receptor sites. This results in effects such as the reduction of smooth muscle contraction. [wiki]
o Diphenhydramine is a potent anticholinergic agent: blocks acetyl choline, inhibiting motion sickness. This leads to profound drowsiness as a very common side-effect, along with the possibilities of motor impairment (ataxia), dry mouth and throat, flushed skin, rapid or irregular heartbeat
o Dopamine Antagonists/Blockers:
· Phenothiazines
o Phenothiazine (Phenegran) – acts by blocking dopamine 2 receptors; inhibiting the CTZ.
o Treats post op/post anesthesia pts, chemo pts, radiation sickness. Also antipsychotic in higher doses.
o May cause hypotension, CNS depression Extrapyrimidal Effects (EPS)
· Butyrophenones
o Haloperdidol (Haldol) – acts by blocking dopamine 2 receptors; inhibiting the CTZ.
o Treats post op/post anesthesia pts, chemo pts
o Side/Adverse effects: May cause hypotension, CNS depression Extrapyrimidal Effects (EPS)
· Benzodiazapines
o Lorazepam (Ativan) – acts by inhibiting the CTZ.
o Indirectly control nausea and vomiting that occur with cancer chemo.
o Lorazepam effectively provides emesis control, sedation, reduction of anxiety, amnesia, with glucocorticoid, H53 receptor antagonist.
· Serotonin (5HT 3) Receptor Antagonists – These block serotonin receptors in CTZ and the afferent (incoming) vagal nerve terminals of the upper GI tract
o Ondsansetron (Zofran) – used to control emesis causes by cancer chemos, and anti-cancer drugs.
o This drug is not a dopamine blocker so it does not cause EPS
o Common side effect is dizziness, nausea and fatigue.
· Glucocorticoids – Used to treat nausea assoc. with chemo. Also used to reduce inflammation.
o Dexamethasone (Decadron) – used to control emesis causes by cancer chemotherapy.
o Administrered IV – only for a short time.
Cannabinoids: Medical Marijuana. Alleviates nausea and vomiting assoc. with cancer treatment, chemo patients, AIDS patients. Also appetite stimulant. Pills don’t work as well as smoking a joint.
o Dronabinol (Marinol) – prescribed for clients who do not respond well to the other antiemetics.
o Contraindicated for those with psychiatric disorders..
· Miscellaneous
o Metoclopramide (Reglan) – acts by blocking dopamine 2 receptors; inhibiting the CTZ.
o Used in treating post-op emesis, cancer chemo, and radiation therapy.
o Adverse: Sedation, diarrhea
ANTIDIARRHEALS
o Opiates and Opiate Related – decrease intestinal motility
o Diphenoxylate w/Atropine (LoMotil) - decrease intestinal motility
o Adverse: Can cause dopiness, drowsiness, dizziness, dry mouth, weakness. Urine retention
o Lomotil: this is for serious watery stools.
o Contrindicated: severe renal, hepatic disease, babies and toddlers
o Somatostatin analogue – decrease intestinal motility
o Octreotide (Sandostatin) – Prescribed to inhibit gastric acid, pepsinogen, gastrin, cholecystokinin, and serotonin secretions, it also decreases smooth muscle activity. Frequently prescribed for diarrhea that results from metastatic cancer.
o Adsorbents – Coat the wall of the intestine [adsorbtion always means coats]
o Kaolin + Pectin (Kaopectate) – Coats the wall of the intestine and adsorbs bacteria or toxins that cause diarrhea.
o Kaopectate: coats the wall of the GI tract.
LAXATIVES
People in the hosp get constipated.
Who has daily diarrhea? The elderly really focus on their BM. These guys abuse laxitives like crazy.
o Osmotic – Sodium Salts
o Sodium Salts (Lactulose) – Hyperosmolar preparations pull water into the intestines to form a soft stool. Salts grab water and keep it in the stool
o Side effects: flatulence, diarrhea, cramps, nausea and vomiting,
o Contraindications: Pts. with diabetes mellitus should avoid becasu eof glucose and fructose.
o Stimulants (contact) – Irritants. Increase peristalsis by irritating sensory neurons in the mucosa.
o Bisacodyl (Dulcolax) – increase intestinal motility by irritating the sensory nerve endings in the intestinal mucosa. Direct effect on smooth muscle.
o For constipation or surgical prep
o Side effects: Can cause abdominal cramping. Life-threatening: tetany
o Bulk Forming – Natural fibrous substances that promote large soft stools by absorbing water into the lg intestine, increasing fecal bulk and peristalsis.
o Psyllium hydrophilic mucilloid (Metamucil) – Must be taken with lg quant of h2o. Insufficient amt. Can cause it to solidify in the GI tract.
o Metamucil: no adverse side effects, bulk former, turns to cement. Can be used as a daily laxative.
o Emollients – Stool softeners. (surface acting or wetting drugs). Lubricants to used to prevent const. Stool softeners; not exactly laxatives. Decrease need for straining. Promote water in the intestine
o Docusate sodium (Colace) – Frequently used to prevent Const. In pts after MI surgery, CVA. They are also given before treatment of fecal impaction.
o Side effects: nausea, diarrhea.
ANTIULCER DRUGS
o Non-systemic Antacid – promote ulcer healing by neutralizing HCL and reducing pepsin activity
o Aluminum Hydroxide – (Amphojel) – Used to treat hyperacidity, peptic ulcer, and reflux esophagitis. Neutralizes gastric acidity. An Alkaline salt.
o Side effect: constipation, long term use can result in GI obstruction.
o Interactions: reduced effect with digitalis; may increase effects of benzodiazepines.
o Contraindications: Pts with acute renal failure – risk of hypermagnesemia.
o Magnesium based antiulcer drugs shouldn’t be given to renal disease patients. The other drugs are aluminum based and they’re ok.
o Histamine2 Blockers – H2 blockers prevent acid reflux in the esophagus by blocking the the H2 receptors of the parietal cells in the stomach, thus reducing gastric acid secretion and concentration.
o Ranitidine (Zantac) – Ranitidine has low protein binding and short half-life. About 50% of the drug is ecreted in the urine unchanged.
o Side effect: headache, dizziness, rash, pruritis, gynecomastia.
o Interactions: Toxicity with Metoprolol (Lopressor). Lowered absorption with antacids. Cardiac dysrhythmias, adverse life-threatening hepatotoxicity.
o Contraindications: Pts with severe renal or liver disease.
o Proton Pump Inhibitors – suppress gastric acid secretion by inhibiting the hydrogen/potassium ATPase enzyme system located in the gastric parietal cells (up to 90% better than H2 blockers)
o Lansoprazole (Prevacid) – Short term treatment for duodenal ulcers, erosive esophagitis. Can be used in large doses to treat H. Pylori infection
o Side effect: headache, dizziness, rash.
o Interactions: may decrease theophylline levels. Liver enzymes must be monitored.
o Contraindications: Pts with severe liver disease.
o Mucosal Protective Drugs – Promote healing by adhering to the ulcer surface and protecting it from gastric secretions.
o Sucralfate (Carafate) – classified as a pepsin inhibitor. Non absorbable, and combines with protein to form a viscous substance to protect it from cid and pepsin – does not neutralize acids or lower acid secretions.
o Side effect: No adverse effects.
o Interactions: reduced effects with tetracycline, phenytoin, fat-sol vits. Digoxin; altered absorption with cipro, antacids..
o Contraindications: Hypesensitivity, renal failure..
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