Summary
Highlights
The video introduces a discussion on gastrointestinal system drugs, specifically antiemetics, antidiarrheals, and laxatives. It begins by reviewing the anatomy relevant to antiemetics, focusing on the chemoreceptor trigger zone (CTZ) and its activation by stimuli like toxins, drugs, balance issues (ears), and neurotransmitters (acetylcholine, dopamine, histamine, serotonin).
The speaker differentiates between nausea, described as a queasy and uneasy feeling of fullness, and vomiting, defined as the rapid expulsion of food. Severe vomiting can lead to dehydration and metabolic alkalosis due to the loss of hydrochloric acid.
Antiemetics are drugs that suppress or stop vomiting. They are categorized into non-prescription and prescription types. Non-prescription antiemetics are often used with non-pharmacologic measures like tea, gelatin, crackers, and increased oral fluid intake. Non-prescription antihistamines (e.g., dimenhydrinate) inhibit vestibular stimulation, preventing motion sickness. They have side effects similar to anticholinergics, such as drowsiness and dry mouth, and are effective if taken 30 minutes before travel but not after vomiting. Other non-prescription antiemetics include bismuth subsalicylate (e.g., Pepto-Bismol), which acts directly on the gastric mucosa, and phosphorated carbohydrates (e.g., Emetrol), which change gastric pH to slightly alkaline and decrease smooth muscle contraction. Bismuth subsalicylate should be avoided in children under 8 due to Reye's syndrome risk and in patients at risk for ulcers/bleeding due to its aspirin-like composition. Phosphorated carbohydrates are contraindicated for diabetic patients due to their carbohydrate base.
Prescription antiemetics, such as dopamine antagonists (phenothiazines like prochlorperazine, butyrophenones like haloperidol, and benzodiazepines like lorazepam), suppress vomiting by blocking dopamine receptors in the CTZ. Phenothiazines are used for nausea and vomiting caused by surgery, anesthesia, and chemotherapy. Butyrophenones are for post-operative, toxin-associated, and radiation therapy-induced nausea and vomiting. Lorazepam offers indirect control. All these drugs are CNS depressants, requiring monitoring for respiratory depression and extrapyramidal symptoms (akathisia, dystonia, parkinsonism, tardive dyskinesia).
Serotonin receptor blockers (e.g., ondansetron) suppress nausea and vomiting by blocking serotonin receptors in the CTZ, particularly effective for chemotherapy-induced nausea and vomiting without EPS side effects. Common side effects include headache, diarrhea, and dizziness. Metoclopramide (Reglan) also blocks dopamine receptors, used for post-operative and chemotherapy-induced nausea and vomiting. High doses can cause sedation and diarrhea, and it is contraindicated in patients with GI obstruction, bleeding, or perforation. It should be administered 30 minutes before meals and at bedtime.
General nursing considerations for all antiemetics include checking vital signs for shock (hypotension, tachycardia, tachypnea), avoiding alcohol if the drug has a sedative effect, monitoring bowel sounds, and advising pregnant patients to avoid antiemetics during the first trimester. Non-pharmacologic measures should be attempted first.
Antidiarrheals treat excessive defecation, which carries a risk of dehydration and hypovolemic shock. General rules dictate not using them for more than 2 days or if fever is present. Diarrhea can lead to metabolic acidosis due to electrolyte imbalances. Various pathologies of diarrhea include osmotic (unabsorbed solutes pulling water into the gut), secretory (excessive fluid secretion into the GI tract), inflammatory (damage to intestinal lining causing blood/protein loss), malabsorptive (failure to absorb nutrients/water), and peristaltic (uncontrolled GI smooth muscle contractions).
Antidiarrheals include opiates and opiate-related drugs (e.g., diphenoxylate with atropine, loperamide), which slow intestinal motility and peristalsis. As CNS depressants, they require caution with alcohol and monitoring for respiratory depression, drowsiness, and dependence. Constipation is a common side effect, and they are contraindicated in hepatic impairment. Naloxone should be prepared for overdose. Anti-secretory agents like octreotide reduce fluid and electrolyte secretion in the GI lumen, leading to solid stools. Absorbents like bismuth subsalicylate and kaolin-pectin coat the GI tract, absorbing bacteria and toxins. Bismuth subsalicylate has similar considerations to its use as an antiemetic, while kaolin-pectin requires administering other PO meds 2 hours before/after to prevent absorption issues and is contraindicated in severe abdominal pain or children under 3.
General nursing considerations for antidiarrheals include monitoring vital signs (especially for shock), frequency of bowel movements, and bowel sounds. Patients should take the drug as prescribed and increase clear fluid intake to prevent dehydration.
Laxatives or cathartics are used to eliminate fecal matter and treat constipation. They should be avoided in cases of intestinal obstruction, appendicitis, ulcerative colitis, and diverticulitis to prevent increased GI pressure and rupture. Constipation is characterized by the inability or difficulty to defecate, caused by pathologies like colonic motility dysfunction, pelvic floor dysfunction, endocrine/metabolic disorders (hypothyroidism, hypercalcemia), bowel obstruction (tumor, adhesions, stenosis), and lifestyle/dietary factors (lack of fiber, fluids).
Osmotic laxatives (e.g., glycerin, lactulose, magnesium citrate, magnesium hydroxide, polyethylene glycol) pull water into the GI tract and increase stool bulk, making it soft. They are used for bowel preparation and constipation. Nursing considerations include monitoring serum electrolytes and renal function, as excessive salt/magnesium can be an issue. Polyethylene glycol (GoLYTELY) is unabsorbable, making it safe for patients with kidney or cardiac disorders, and can be used in large amounts for pre-surgical bowel prep. Stimulant laxatives (e.g., bisacodyl, senna, castor oil) increase peristalsis by irritating sensory nerve endings in the GI tract. Bisacodyl is used to empty the bowel before diagnostic exams, while senna is often abused. Castor oil is a rapid purgative. Nursing considerations include monitoring for fluid/electrolyte imbalances, especially decreased potassium and calcium, and avoiding overuse. Castor oil is contraindicated in pregnant patients, and increased oral fluid intake and a high-fiber diet are encouraged.
Bulk-forming laxatives (e.g., polycarbophil, methylcellulose) absorb water, increasing stool bulk and peristalsis, resulting in large, soft stools. Polycarbophil and polyethylene glycol are non-absorbable and suitable for patients with kidney or cardiac disorders. These are non-addictive. Common side effects include nausea, vomiting, flatus, and diarrhea. If powdered, they must be mixed with water to avoid GI obstruction. Emollients or stool softeners (e.g., mineral oil, docusate sodium) lubricate the GI tract and soften stool, reducing straining during defecation. They are used for preventing constipation and treating fecal impaction. Docusate is more potent than mineral oil. Key nursing considerations include giving emollients prior to other laxatives to soften stool and reduce straining. Side effects include nausea, diarrhea, and abdominal cramping, and they are contraindicated in inflammatory bowel disorders and pregnancy. The video concludes by reiterating the inverse relationship between antidiarrheals and laxatives and briefly mentions emetics (e.g., ipecac) which induce vomiting but are no longer widely used.