Anti-emetics

Gastrointestinal (GI) Disorders
  - GI tract infection and inflammation
  - Affected organs: liver, gallbladder, pancreas
  - Impaired GI motility
  - Impaired GI muscle tone
  - Overeating or ingestion of irritating foods or fluids that affect GI mucosa

Definition: Medications used to prevent or treat nausea and vomiting.
  - Nausea: Unpleasant sensation of abdominal discomfort accompanied by a desire to vomit.
  - Vomiting: Expulsion of stomach contents through the mouth.
  - Emesis: Term for the actual stomach contents produced during vomiting.
  - Emetogenic: Referring to substances or conditions that induce vomiting.

In Pregnancy: Activation of the Chemoreceptor Trigger Zone (CTZ) plays a significant role.
In Motion Sickness: Stimulation of inner ear receptors.
Vomiting Center: Located in the medulla oblongata; it is activated during vomiting episodes.
Signals: From the CTZ, cerebral cortex, sensory organs, and vestibular apparatus.
Key Neurotransmitter Receptors:
  - Serotonin
  - Dopamine
  - Histamine H1
  - Cholinergic (muscarinic)

Characteristics: Central nervous system (CNS) depressants used for various reasons.
Applications: Also used as antipsychotics.
Prototype: Prochlorperazine.
Routes of Administration: Oral (PO), Intramuscular (IM), Intravenous (IV); IM is preferred.
Pharmacokinetics: Undergoes extensive first-pass metabolism, excreted in urine.
Mechanism of Action: Ability to block dopamine from binding to receptor sites in the brain and CTZ.

Uses: Prevention and treatment of N/V related to surgery, anesthesia, migraines, chemotherapy, and motion sickness.
Adverse Effects:
  - Anticholinergic effects: dry mouth, urinary retention
  - Drowsiness and confusion
  - Less common but serious: respiratory depression.
Nursing Implications: Administer before N/V onset for effective prevention.

Classification: Anti-nausea potential with classic H1 receptor blocking agents (distinguished from H2 receptor blocking agents like cimetidine).
Note: Not all antihistamines exhibit antiemetic effects.
Prototype: Hydroxyzine.
Routes of Administration: Oral (PO), Intramuscular (IM).
Pharmacokinetics: Metabolized in the liver; main metabolite is cetirizine; excreted in urine.

Mechanism of Action: Exact action is unclear; believed to block acetylcholine in the brain.
Uses: N/V, motion sickness, anxiety.
Adverse Effects:
- Anticholinergic effects: drowsiness, dizziness, confusion, dry mouth, thickened respiratory secretions, blurred vision, urinary retention, tachycardia.
Drug Interactions: Notable interaction with other CNS depressants leading to increased CNS depression.
Contraindications: Hypersensitivity only.

Consideration: These are usually first-choice drugs for postoperative nausea and vomiting.
Prototype: Ondansetron.
Routes of Administration: Oral (PO), Intravenous (IV), Intramuscular (IM).
Pharmacokinetics: Some first-pass metabolism; metabolized in the liver, excreted in urine.
Mechanism of Action: Prevent activation of serotonin receptors.
Uses: Postoperative N/V and chemotherapy-induced N/V (for patients over 6 months).

Adverse Effects: Diarrhea, headache, dizziness.
Drug Interactions: Avoid use with apomorphine due to risks of hypotension and potential unconsciousness.
Contraindications: Only sensitivity.

Overview: A peptide neurotransmitter in the neurokinin family.
Role: Mediates acute chemotherapy-induced N/V and believed to be the primary mediator for delayed nausea and vomiting associated with chemotherapy.

Prototype: Aprepitant.
Routes of Administration: Oral (PO), Intravenous (IV).
Pharmacokinetics: Metabolized in liver, excreted in urine and feces; involves the CYP 450 system.
Mechanism of Action: Blocks activity of substance P, inhibiting nausea signals transmitted to the brain.
Uses: Commonly used in combination therapy for postoperative N/V and with chemotherapy.

Adverse Effects: Fatigue, dizziness, abnormal heart rhythm.
Drug Interactions: Numerous interactions noted.
Contraindications: Hypersensitivity; do not administer with ranolazine, pimozide, or cisapride.

Description: A derivative of marijuana.
Debate: Should it be used for N/V?
- Concerns: High potential for abuse, withdrawal syndrome upon abrupt cessation, and sleep disturbances.
- Current Alternatives: Present medications are more effective for managing N/V.

Assessment: Identify risk factors and current medications.
Prevention: Aim to minimize or prevent N/V; identify and mitigate aggravating factors.
Environmental Control: Avoid exposure to noxious stimuli (e.g., unpleasant sights, odors, excessive food/alcohol/NSAIDs).
Administration of Analgesics: Given prior to painful procedures to reduce N/V triggers.

Administer antiemetic drugs 30 to 60 minutes before anticipated nausea-producing events (e.g., radiation therapy, cancer chemotherapy, travel).
Adjust timing for oral drugs causing gastric irritation by administering with or immediately following meals.
Reporting: Document N/V occurrences and re-evaluate medication if N/V persists or worsening occurs, consider NG tube if necessary.
Morning Sickness: Recommendations include eating dry crackers before rising and consuming small, frequent protein meals.
Oral Intake During N/V: Avoid food, fluids, and drugs during episodes to decrease risk of worsening vomiting and fluid/electrolyte imbalances.
Minimize activity, rest quietly, and reduce environmental stimuli during episodes.
Supportive Care: Provide emotional support during vomiting episodes; assist with mouth rinse post-emesis to combat taste and enamel erosion from gastric acid.
Additional comfort measures: cool washcloths, back rubs as appropriate.
Education: Provide thorough education regarding any drug therapy administered.

Vital Signs: Record vital signs, intake and output, and body weight regularly if frequent N/V occurs.
Supportive Care: Offer replacement fluids and electrolytes, and allow for small oral intakes when tolerated.

Frandsen, G. & Pennington, S.S. (2025). Abram's clinical drug therapy: Rationales for nursing practice (13th ed.). Wolters Kluwer.