Drugs Acting on the Gastrointestinal System: Chapter 59 – Antiemetic Agents

Comprehensive vocabulary flashcards covering the mechanism of action, therapeutic indications, adverse effects, and contraindications of phenothiazines, serotonin receptor blockers, and cannabinoids as presented in Chapter 59.

Emetic Zone (Vomiting Center)

A center in the medulla that initiates projectile vomiting when stimulated (usually by hypoxia); seen in young children and when increased intracranial pressure or brain damage allows it to override the CTZ.

Chemoreceptor Trigger Zone (CTZ)

An area in the medulla that triggers vomiting when stimulated by throat tactile stimulation, GI inflammation/distention, increased ICP, vestibular stimulation, bladder/uterine stretch, intense pain, or direct chemicals and drugs.

Phenothiazines

A class of dopamine receptor antagonists (including chlorpromazine, perphenazine, prochlorperazine, and promethazine) that act in the medulla to change the responsiveness of the CTZ, treating severe nausea and vomiting, anesthesia-related emesis, and hiccups.

Promethazine

A phenothiazine dopamine receptor antagonist that is contraindicated in patients younger than 2 years of age and used with caution in all other pediatric patients.

Phenothiazine Dementia Warning

An increased risk of mortality that occurs when older adults with dementia-related psychosis are administered drugs with antipsychotic properties.

Pink-Red Brown Urine

A harmless, normal drug effect observed in patients taking phenothiazines.

Extrapyramidal Symptoms (EPS)

Movement disorder adverse effects of phenothiazines that include tardive dyskinesia, tremors, and muscle spasms.

Serotonin Receptor Blockers

Antiemetic medications (ondansetron, palonosetron, granisetron) that decrease nausea and vomiting by blocking serotonin receptors locally and in the CTZ.

Serotonin Receptor Blocker Adverse Effects

Adverse effects including headache (treated with non-opioid analgesics), dizziness, myalgia, and dysrhythmias (which require ECG monitoring).

Dronabinol

A cannabinoid agent that activates cannabinoid receptors to induce marijuanalike effects; approved for treating nausea and vomiting in chemotherapy patients and anorexia in patients with AIDS.

Cannabinoid Psychiatric Adverse Effects

Adverse drug effects including euphoria, altered cognition/thinking, sedation, and paranoia, with the potential to enhance existing depression, mania, or schizophrenia.