Pharmacology: Antiemetic Medications

Vocabulary flashcards covering antiemetic classes, mechanisms of action, specific drug examples, adverse effects, and nursing considerations from NU 320 Pharmacology.

Vomiting Center

A structure located in the medulla that receives input from the GI tract, vestibular system, and cerebral cortex to trigger emesis.

Chemoreceptor Trigger Zone (CTZ)

A region in the brain that detects chemical changes in the blood or cerebrospinal fluid to trigger nausea and vomiting.

Anticholinergics

An antiemetic class that binds to and blocks ACh receptors in the inner ear and vestibular nuclei in the brain, indicated for motion sickness, vestibular disorders, and post-op nausea.

Scopolamine

An anticholinergic patch antiemetic used for motion sickness and post-op nausea; can cause anticholinergic toxidrome, which is more concerning in adults and usually resolves with patch removal.

Antihistamines (Antiemetics)

An antiemetic class that blocks H1 receptors in the area postrema and vomiting center; possesses anticholinergic effects and side effects including drowsiness and dizziness.

Promethazine (Phenergan)

An antihistamine antiemetic administered orally or IM, but never IV due to severe tissue necrosis.

Hydroxyzine (Vistaril)

An antihistamine antiemetic administered orally or IM, but never IV due to the risk of tissue necrosis.

Dopamine Receptor Antagonists

An antiemetic class that blocks D2 receptors in the CTZ and GI tract, indicated for N/V, gastroparesis, and delayed gastric emptying.

Metoclopramide (Reglan)

A dopamine receptor antagonist that also acts as a prokinetic by enhancing motility through peristalsis and muscle tone; contraindicated in bowel obstruction.

Extrapyramidal Symptoms (EPS)

Adverse effects of dopamine receptor antagonists involving muscle rigidity, tremors, restlessness, involuntary movements, dystonia, parkinsonism, akathisia, and tardive dyskinesia; treated with diphenhydramine (Benadryl).

Neuroleptic Malignant Syndrome (NMS)

A rare, life-threatening condition caused by dopamine inhibition that disrupts muscle control, temperature regulation, and autonomic function.

Serotonin Receptor Antagonists

An antiemetic class that blocks 5-HT3 serotonin receptors in the CTZ and GI tract, indicated for chemotherapy and post-op N/V.

Ondansetron (Zofran)

A serotonin receptor antagonist indicated for chemo and post-op N/V; best given prophylactically, with constipation as a common side effect.

Serotonin Syndrome

A condition caused by excessive serotonin activity leading to hyperthermia, hyperreflexia, altered mental status, and autonomic instability; carries a black box warning when serotonin blockers are used concurrently with SSRIs, SNRIs, or TCAs.

Cannabinoids (THC)

An antiemetic class that stimulates cannabinoid receptors in the vomiting center and exerts an inhibitory effect in the reticular formation, thalamus, and cerebral cortex; e.g., dronabinol (Marinol).

Substance P / Neurokinin Antagonists

An antiemetic class that inhibits substance P/neurokinin in the brainstem to reduce vomiting, augmenting the action of ondansetron and steroids.

Aprepitant (Emend)

A substance P/neurokinin antagonist used prophylactically for chemo and post-op nausea; increases Warfarin metabolism, requiring INR monitoring.