Gastrointestinal Flashcards
What drugs are used for Nausea causing stimulants: Drugs, Ketoacidosis, Uremia
Phenothiazines
Metaclopramide
Work in the CTZ (dopamine, opiate receptors)
What drugs are used for nausea causing stimulants: Obstruction, Gastroparesis, Visceral Pain
Metaclopramide
Analgesics
Work on the afferent impulses from the periphery (dopamine, opiate receptors)
What drugs are used for nausea causing stimulants: Motion sickness, vestibular inflammation
Antihistamines
Anticholinergics
Work in the vestibular apparatus (acetylcholine, norepinephrine receptors)
What drugs are used for nausea causing stimulants: Higher brain stem (Emotions, Sights, Smells, Tastes)
Benzodiazepines
Dronabinol
Corticosteroids
Work in the cortical structures
CTZ location and mechanism
Located in the area postrema on the fourth ventricle floor of the Medulla
Exposed to both blood and CSF - toxins in the blood can stimulate a response in the CTZ
GI tract nausea stimulants MOA
Visceral afferent nerves - splanchnic nerves - from the pharynx and GI tract transmit impulses along the vagus nerve to the vomiting center
CNS nausea stimulants MOA
Motion sickness is a CNS mediated response by the vestibular system.
Acetylcholine and histamine receptors in the vestibular center need to be blocked to block the effects of nausea
Limbic system nausea stimulants MOA
Increased ICP can stimulate nausea. Higher brain functions - emotions, mood, feelings, memory - can trigger a nausea response
What are the physiologic symptoms of nausea?
Flushing, pallor, tachycardia, hyper salivation, gstric stasis and decreased pyloric tone, mucosal blood flow, and duodenal contractions iwth reflux into the stomach
What is retching?
The second phase of emesis.
The involuntary synchronized labored movement of the abdominal and thoracic muscles before vomiting.
What is vomiting?
The coordinated contractions of the abdominal and thoracic muscles to expel the gastric contents
Phenothiazines (Prochlorperazine / Compazine; Promethazine / Phenergan) MOA:
Dopamine receptor blockade in the CTZ.
Anticholinergic activity in the vomiting and vestibular centers
Phenothiazines (Prochlorperazine / Compazine; Promethazine / Phenergan) Indications:
Monotherapy or combo for mild to moderate nausea and vomiting. IV, PO, Rectal, IM
Migraine, GI d/o, CINV, Sedative properties
Phenothiazines (Prochlorperazine / Compazine; Promethazine / Phenergan) CXN:
BEERS criteria
CNS depression
High doses = extrapyramidal symptoms (by blocking central dopaminergic receptors) - Tx with Benadryl
Decrease Sz threshold
Contraindicated: Parkinson’s Dz, Sz d/o
Antihistamines-Anticholinergics (Hydroxazine/Vistaril, Atarax; Meclizine/ Bonine, Antivert; Dimenhydrinate / Dramamine; Scopolamine / Transderm Scop) MOA:
Antihistamine MOA: Block H1 receptors in vestibular system and brainstem preventing signaling to vomiting center
Anticholinergic MOA: Block muscarinic receptors in the vestibular system and the vomiting center inhibiting PNS and reduce communication between vestibular and vomiting center