Brainscape Flashcards - emetics
What triggers vomiting?
Stimulation of the emetic center in the medulla oblongata.
Where is the vomiting center located in the brain?
In the medulla oblongata.
Which area is unprotected by the blood-brain barrier and can be triggered by blood-borne substances?
Chemoreceptor trigger zone (CTZ).
Which neurotransmitters and receptors are involved in the emetic signaling pathway?
Histamine H1, dopamine D2, serotonin 5-HT3, cholinergic M, and opioid μ receptors.
How does the vestibular apparatus contribute to vomiting?
It generates impulses when equilibrium is disturbed, affecting the vomiting center via muscarinic and H1 receptors.
What are some common triggers of nausea and vomiting from higher centers?
Unpleasant sensory stimuli, fear, recall of an obnoxious event, and anticipation of an emetic stimulus.
What is the role of serotonin (5-HT) in emesis?
Released from enterochromaffin cells in the GI tract, it activates 5-HT3 receptors, stimulating vomiting.
Name two situations where vomiting is induced.
When a poison or other undesirable substance is ingested.
Name two drugs that act as emetics by acting on the CTZ.
Apomorphine and Ipecacuanha.
What is apomorphine, and how does it induce vomiting?
A semisynthetic derivative of morphine; acts as a dopaminergic agonist on the CTZ.
In which situations are emetics contraindicated?
In corrosive, CNS stimulant drug, kerosine poisoning, unconscious patients, or morphine/phenothiazine poisoning.
What is the main drug class used to prevent or suppress vomiting?
Antiemetics.
Name one anticholinergic drug effective for motion sickness.
Hyoscine.
What is the function of dicyclomine in treating vomiting?
It is used for prophylaxis of motion sickness and morning sickness.
What is the main effect of H1 antihistamines in antiemesis?
They work primarily by their anticholinergic, antihistaminic, and sedative properties.
Which drug class includes promethazine, diphenhydramine, and cyclizine?
H1 antihistamines.
How do neuroleptics function as antiemetics?
By blocking D2 receptors in the CTZ.
What is the action of neuroleptics on the CTZ?
They block D2 receptors, making them effective in drug-induced and disease-related vomiting.
What is metoclopramide’s role in gastrointestinal (GI) transit?
It promotes GI transit by enhancing gastric motility and speeding gastric emptying.
Why is metoclopramide not recommended for long-term use?
Long-term use can cause parkinsonism, galactorrhea, and gynecomastia.
Which drug class can enhance antiemetic action when combined with other antiemetics?
Corticosteroids, benzodiazepines, cannabinoids.
Name a 5-HT3 antagonist used for chemotherapy-induced vomiting.
Ondansetron.
What side effects are associated with the use of 5-HT3 antagonists like ondansetron?
Common side effects include headache, mild constipation, or diarrhea.
How do corticosteroids help in antiemetic therapy?
They are used to alleviate nausea and vomiting in moderately emetogenic chemotherapy and enhance other antiemetic drugs.
