Antiemetics and Antinausea Drugs

Nausea and Vomiting

• The chemoreceptor trigger zone sends signals to the vomiting center
• Nausea and vomiting can be triggered by noxious stimuli
• Key signaling molecules are Ach, D2, H1, PG, and S (5-HT3)

Sites of Action for Antinausea Drugs

• Gastrointestinal Tract: Prokinetic drugs and serotonin blockers act here
• Labyrinth (inner ear): Anticholinergics, antihistamines, neuroleptics, and prokinetic drugs are effective
• Chemoreceptor Trigger Zone (CTZ): Neuroleptics, prokinetic drugs and serotonin blockers work in this area
• Cerebral Cortex: Tetrahydrocannabinol (THC), corticosteroids, and benzodiazepines have an effect
• Vomiting Center (medulla): Serotonin blockers are the primary treatment

Antiemetics and Antinausea Drugs - Classes

• Anticholinergic drugs
• Antihistamines (H₁ receptor blockers)
• Antidopaminergic drugs
• Prokinetic drugs
• Serotonin blockers
• Tetrahydrocannabinoids

Antiemetics and Antinausea Drugs - MOA

• Antiemetics and antinausea drugs have several mechanisms of action
• The majority of them function by blocking one of the vomiting pathways

Antihistamine Drugs

• Inhibit acetylcholine by binding to H₁ receptors
• Prevent cholinergic stimulation in vestibular and reticular areas
• Treat motion sickness, nonproductive cough, allergy symptoms, and sedation
• Examples include dimenhydrinate (Gravol®) and diphenhydramine (Benadryl®)
• Do not administer Hydroxyzine IV because it may cause cause 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 can cause amputation if given IV, so it should only be given PO or IM.

Anticholinergic Drugs

• Block acetylcholine receptors in the inner ear labyrinth
• Block transmission of nauseating stimuli to the CTZ
• Scopolamine is an example
• Contraindicated in patients with glaucoma

Prokinetic Drugs

• Block dopamine receptors in the CTZ
• They desensitize the CTZ to impulses from the GI tract
• Stimulate peristalsis in the GI tract, enhancing emptying of stomach contents
• Can be used for gastroesophageal reflux disease and delayed gastric emptying
• Metoclopramide is an example

Serotonin Blockers

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

Tetrahydrocannabinoids

• Major psychoactive substance in cannabis
• Can have inhibitory effects on the reticular formation, thalamus, and cerebral cortex
• They alter mood and body’s perception of its surroundings, which may help relieve nausea and vomiting
• It can be used for chemotherapy and anorexia associated with weight loss in acquired immune deficiency syndrome (AIDS) patients

Miscellaneous Antinausea Drugs

• Aprepitant
• Doxylamine succinate and pyridoxine hydrochloride is a combination of antihistamine and vitamin B6 used for morning sickness

Herbal Products: Ginger

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

Nursing Implications for Antiemetics

• Many antiemetics cause severe drowsiness
• Warn patients about driving or performing hazardous tasks
• Taking antiemetics with alcohol may cause severe central nervous system depression
• Teach patients to change positions slowly to avoid hypotensive effects
• For chemotherapy, give antiemetics 30 to 60 minutes before chemotherapy begins

Question - Ginger Interactions

• It is important for the nurse to determine if the patient is taking warfarin (Coumadin®) when taking ginger for nausea due to the increased bleeding risk

Enteral Nutrition Defined

• Feeding tubes provide nutrition to patients with abnormal peristalsis, digestive capacity, altered anatoly secondary to surgery, or depressed consciousness

Enteral Nutrition - Types

• Elemental
• Polymeric
• Modular (carbohydrate, fat or protein formulations)
• Altered amino acid formulations
• Impaired glucose tolerance

Elemental Enteral Nutrition

• Includes Peptamen®, Vital HN®, Vivonex Plus®, and Vivonex® T.E.N.
• Requires minimal digestion, resulting in minimal residual
• Administered for malabsorption, partial bowel obstruction, irritable bowel disease, and other conditions
• High osmolarity may cause gastrointestinal problems

Polymeric Enteral Nutrition

• Includes Complete®, Ensure®, Ensure Plus®, Isocal®, Osmolite®, Portagen®, Jevity®, and Sustacal®
• Preferred over elemental formulations for patients with fully functional GI tracts and few specialized nutrient requirements
• They cause fewer gastrointestinal problems
• Closely resemble normal dietary intake

Modular Enteral Nutrition

• Consists of single-nutrient formulas for use with monomeric or polymeric formulations
• Three types include:
  • Carbohydrates: Moducal®, Polycose®
  • Fat: MCT Oil®, Microlipid®
  • Protein: Beneprotein®, ProMod®

Altered Amino Acid Enteral Nutrition

• Examples include Amin-Aid®, Primene®, TwoCal®, TwoCal HN®, and Travasol®
• Contain varying amounts of specific amino acids for patient with diseases associated with altered metabolism capacities

Impaired Glucose Tolerance Enteral Nutrition

• Example is Glucerna and it contains proteins, carbohydrates, fat, sodium, and potassium
• Used in patients with impaired glucose tolerance (e.g., diabetes)

Enteral Nutrition: Adverse Effects

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

Nursing Implications for Enteral Nutrition

• Follow facility policy for tube placement and checking residual volumes before administering
• Follow procedures for flushing tubing to prevent clogging
• Monitor for signs of intolerance
• Start feedings slowly and increase the rate gradually
• Monitor for signs of lactose intolerance

Parenteral Nutrition

• Provides totally digested nutrients intravenously, bypassing the entire GI system
• Also known as 'Hyperalimentation' or total parenteral nutrition (TPN)
• Formulations containing Calories, Amino acids, Carbohydrates, Fats, Trace Elements, Vitamins, Minerals, will vary according to individual patient nutritional needs

Parenteral Nutrition: Peripheral vs. Central

• Peripheral TPN: Short-term, temporary (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 when present oral intake is not sufficient
• Indicated by procedures that restrict oral feedings, anorexia, Gl illnesses that prevent oral intake, and postsurgical patients.
• Used when nutrition deficits are minimal, with oral nutrition will not be started for more than 5 days
• Presents a high risk for Phlebitis

Central Total Parenteral Nutrition

• Delivered through a large central vein via the subclavian or internal jugular
• Indicated for long-term use (more than 7 to 10 days)
• Has risks associated with central line use, and maintenance as well as Catheter-induced trauma, and metabolic alterations
• Can result in Infection, and a Greater chance for hyperglycemia

Nursing Implications: TPN

• Follow facility policies and procedures for care and maintenance of TPN IV lines, including tubing and dressing changes
• Report any increase to patient temperature immediately
• Monitor blood glucose levels with a glucometer because patients are at risk of hyperglycemia
• Monitor for headache, dehydration, weakness as symptoms of hyperglycemia
• Monitor for hypoglycemia, indicated by Cold, clammy skin, dizziness, tachycardia, and tingling of the extremities

Nursing Implications: Glucose with Parenteral Nutrition

• Increased amounts of insulin provide coverage during TPN
• Rebound hypoglycemia may occur if TPN is discontinued abruptly
• If TPN must be discontinued abruptly, infuse 5 to 10% glucose to prevent hypoglycemia

Nursing Implications: Fluid Overload with Parenteral Nutrition

• Monitor for fluid overload which is indicated by Weak pulse, Hypertension, Tachycardia, Confusion, Decreased urine output, and Pitting edema
• Monitor daily weights and intake and output volumes.

TPN Policies and Procedures

• Protocols will be Agency specific and may include HSN TPN order set and HSN Procedure
• Check Daily labs, lipid profile, and INR
• Monitor Glucose Q6H
• Weights Q Mondays and Thursdays
• TPN can be held for blood administration, in which case the rate may need to be changed

Long Term Complications of Parenteral Nutrition

• Progressive fibrosis and cirrhosis of the liver
• Short bowel-syndrome
• Sepsis