Antiemetics and Antinausea Drugs

Nausea and Vomiting

• The chemoreceptor trigger zone sends signals to the vomiting centre when noxious stimuli are present.
• Key chemicals involved in this process: Ach, D2, H1, PG, and S (5-HT3)

Antiemetics and Antinausea Drugs

• This class of drugs works through many different mechanisms of action
• Work by blocking one of the vomiting pathways

Antihistamine Drugs

• Inhibit acetylcholine by binding to H1 receptors
• Prevent cholinergic stimulation in vestibular and reticular areas
• Uses include motion sickness, nonproductive cough, allergy symptoms, and sedation
• Examples include dimenhydrinate (Gravol®) and diphenhydramine (Benadryl®)
• Hydroxyzine should never be administered IV due to the risk of tissue damage, thrombosis, and gangrene

Antidopaminergic Drugs

• Block dopamine receptors in the chemoreceptor trigger zone
• Used for psychotic disorders and intractable hiccups
• Examples include prochlorperazine (Proclorazine®) and promethazine hydrochloride (Histanil®)
• Promethazine must be administered orally or intramuscularly because IV administration can cause intra-arterial damage and lead to amputation

Anticholinergic Drugs

• These bind to and block acetylcholine receptors in the inner ear labyrinth
• They block transmission of nauseating stimuli to the Chemoreceptor Trigger Zone (CTZ)
• Scopolamine is one such drug
• They are contraindicated in cases of glaucoma

Prokinetic Drugs

• They function by blocking dopamine receptors in the CTZ
• They may cause CTZ to be desensitized to impulses it receives from the GI tract
• They stimulate peristalsis in the GI tract, enhancing stomach emptying
• Used for gastroesophageal reflux disease and delayed gastric emptying
• Metoclopramide is an example

Serotonin Blockers

• Block serotonin receptors in the GI tract, CTZ, and vomiting centre
• Useful for chemotherapy and postoperative nausea and vomiting
• Examples include ondansetron (Zofran®) and palonosetron (Aloxi®)
• IV administration increases the risk of dysrhythmia
• Ondansetron can be given IV push up to 8mg over 5 minutes

Tetrahydrocannabinoids

• The major psychoactive substance in cannabis, impacting the reticular formation, thalamus, and cerebral cortex
• Alters mood and the body's perception of surroundings, potentially relieving nausea and vomiting
• Used for chemotherapy-induced nausea and anorexia associated with weight loss in AIDS patients

Miscellaneous Antinausea Drugs

• Aprepitant is an example
• Doxylamine succinate and pyridoxine hydrochloride (antihistamine + vitamin B6) are used for morning sickness

Herbal Products: Ginger

• Adverse effects: anorexia, nausea and vomiting, skin reactions
• May increase the absorption of oral medications and increase bleeding risk with anticoagulants

Nursing Implications for Antiemetics

• Many antiemetics cause severe drowsiness, so patients should be warned about activities like driving
• Taking antiemetics with alcohol can cause severe central nervous system depression
• Advise patients to change positions slowly to avoid hypotensive effects
• For chemotherapy, antiemetics should be given 30 to 60 minutes before chemotherapy begins

Enteral Nutrition Application

• Applied to patients with abnormal esophageal or stomach peristalsis, altered anatomy secondary to surgery, depressed consciousness, and impaired digestive capacity
• Includes:
  • Elemental
  • Polymeric
  • Modular
  • Altered amino acid formulations
  • Impaired glucose tolerance

Elemental Enteral Nutrition

• Examples: Peptamen®, Vital HN®, Vivonex Plus®, Vivonex® T.E.N.
• Minimal digestion is needed, so residual is minimal
• Used for malabsorption, partial bowel obstruction, and irritable bowel disease
• Hyperosmolarity of formulas may cause gastrointestinal problems

Polymeric Enteral Nutrition

• Examples: Complete®, Ensure®, Ensure Plus®, Isocal®, Osmolite®, Portagen®, Jevity®, Sustacal®
• Preferred over elemental formulations for patients with fully functional GI tracts and few specialized nutrient requirements because it causes fewer gastrointestinal problems
• Most closely resembles normal dietary intake

Modular Enteral Nutrition

• Includes carbohydrate, fat, and protein types
  • Carbohydrate: Moducal®, Polycose®
  • Fat: MCT Oil®, Microlipid®
  • Protein: Beneprotein®, ProMod®
• Used as single-nutrient formulas with monomeric or polymeric formulations

Altered Amino Acid Enteral Nutrition

• Examples: Amin-Aid®, Primene®, TwoCal®, TwoCal HN®, Travasol®
• Varying amounts of amino acids address diseases with altered metabolism capacities

Impaired Glucose Tolerance Enteral Nutrition

• Glucerna is used to address
• Includes proteins, carbohydrates, fat, sodium, and potassium
• Designed for patients with impaired glucose tolerance, such as those with diabetes

Enteral Nutrition: Adverse Effects

• Gastrointestinal intolerance: diarrhea
• Dumping syndrome causes nausea, weakness, sweating, palpitations, syncope, sensations of warmth, and diarrhea
• Aspiration pneumonia

Nursing Implications for Enteral Nutrition

• Follow facility policy for ensuring proper tube placement and checking residual volumes before administering feedings
• Follow procedures for flushing tubing to prevent clogging with formula
• Carefully monitor how the patient is tolerating feedings, starting slowly and increasing the rate gradually
• Monitor for signs of lactose intolerance

Parenteral Nutrition

• Totally digested nutrients are given intravenously, bypassing the entire GI system
• ‘Hyperalimentation' or total parenteral nutrition (TPN)
• Formulations vary according to individual patient nutritional needs with calories, amino acids, carbohydrates, fats, trace elements, vitamins, and minerals

Parenteral Nutrition: Peripheral vs. Central

• Peripheral TPN
  • Temporary, short term (less than 2 weeks)
  • Dextrose concentration less than 10%
• Central TPN
  • Long-term use (longer than 7 to 10 days)
  • Dextrose concentrations may be 10 to 50% but are commonly 25 to 35%.

Peripheral Total Parenteral Nutrition

• Used to provide nutrients that present oral intake can not provide
• Used for:
  • Procedures that restrict oral feedings
  • Anorexia caused by chemotherapy or radiation treatments
  • Gastrointestinal illnesses that prevent oral food intake
  • Postsurgical patients
  • When nutrition deficits are minimal but oral nutrition will not be started longer than 5 days
• Risk of phlebitis is high

Central Total Parenteral Nutrition

• Delivered through a large central vein such as the subclavian or internal jugular
• For long-term use (more than 7 to 10 days)
• Risks associated with central line insertion, use, and maintenance exist
• Catheter-induced trauma, metabolic alterations
• There is a potential for infection
• Hyperglycemia risk because of the larger and more concentrated volumes given

Nursing Implications: TPN

• Follow facility policies for care and maintenance of TPN IV lines, including tubing and dressing changes
• Monitor patient’s temperature, report any increase immediately, and monitor blood glucose levels with a glucometer
• Watch for hyperglycemia with headache, dehydration, and weakness
• Monitor for hypoglycemia with cold, clammy skin; dizziness; tachycardia; and tingling of the extremities

Nursing Implications: Glucose for TPN

• While on TPN, the pancreas provides increased insulin to cover the increased glucose levels
• If TPN is discontinued abruptly, rebound hypoglycemia may occur until the pancreas has time to adjust to changing glucose levels
• If TPN must be discontinued abruptly, infuse 5 to 10% glucose to prevent hypoglycemia

Nursing Implications for TPN Patients

• Watch for and monitor for fluid overload
  • Weak pulse
  • Hypertension
  • Tachycardia
  • Confusion
  • Decreased urine output
  • Pitting edema
• Monitor daily weights and intake and output volumes

Long Term

• Can result in progressive fibrosis and cirrhosis of the liver
• Short bowel-syndrome
• Sepsis