Dopamine Antagonists in Medicine

Study Notes

Dopamine Antagonists

Block dopamine 2 receptors in the chemoreceptor trigger zone (CTZ).
Phenothiazines (e.g., Promethazine, Prochlorperazine, Thorazine) are effective for severe nausea from surgery, anesthesia, chemotherapy, and radiation.
Doses used are smaller compared to psychiatric treatments, with rapid onset via IV or IM routes.
Potential side effects include hypotension, sedation, extrapyramidal symptoms (EPS), dry mouth, constipation, and urinary retention.

Butyrophenones and Metoclopramide

Common agents include Haldol and Inapsine.
Long-term use can result in EPS; blood pressure should be monitored due to the risk of hypotension.
Metoclopramide can cause sedation and diarrhea at high doses and should not be administered with gastrointestinal obstruction, hemorrhage, or perforation.
EPS is more frequent in children.

Benzodiazepines and Serotonin Receptor Antagonists

Benzodiazepines like Lorazepam and Diazepam indirectly manage nausea and vomiting associated with chemotherapy.
Serotonin receptor antagonists, including Ondansetron (Zofran), are used specifically for nausea and vomiting induced by cancer chemotherapy without causing EPS.
Common side effects for these agents include headaches, diarrhea, dizziness, and fatigue.

Glucocorticoids and Cannabinoids

Used to treat nausea and vomiting related to cancer treatment; glucocorticoids are administered IV and used short-term to minimize side effects.
Cannabinoids are derived from marijuana but should not be given to patients with psychiatric disorders; side effects may include mood changes, euphoria, dizziness, and confusion.

Poisoning/Overdose Treatment

Gastric lavage and activated charcoal are standard procedures.
Specific antidotes include:
- Acetaminophen: Mucomyst
- Narcotics: Narcan
- Benzodiazepines: Flumazenil
- Lanoxin: Digibind
- Warfarin and Xarelto: Vitamin K
- Heparin: Protamine sulfate

Diarrhea Management

Can lead to severe electrolyte imbalances or dehydration if prolonged; antidiarrheals should not be used for more than two days or if fever is present.
Treatment aims to decrease diarrhea and hypermotility.
Common antidiarrheals include opiates (e.g., tincture of opium, Imodium); potential side effects include CNS depression and dependence.

Constipation Remedies

Prevention strategies consist of a high-fiber diet, increased water intake, and regular exercise.
Laxatives or cathartics may be utilized, but they are contraindicated in cases of intestinal obstruction, appendicitis, ulcerative colitis, or diverticulitis.
Laxative abuse should be avoided to prevent dependence.
Types of laxatives include:
- Osmotics (saline) - contraindicated in poor renal function or CHF.
- Stimulants (contact or irritant).
- Bulk forming.
- Emollients (stool softeners).

Antiulcer Drugs and Gastrointestinal Agents

Peptic ulcers can occur in the stomach, esophagus, duodenum, or upper GI region, named by their location.
Caused by hypersecretion of hydrochloric acid and pepsin, which erodes the GI mucosal lining.
The gastric mucosal barrier (GMB) provides protection against corrosive substances.

Description

This quiz covers the properties and effects of dopamine antagonists, including their use in treating nausea from surgery, anesthesia, and chemotherapy. It also discusses their side effects and administration methods.