Nausea, Vomiting, Diarrhea and Constipation Flashcards
What receptors are located within the vomiting center in the brain?
Acetylcholine
Dopamine
5- FHT3 (seratonin)
Histamine
How is the vomiting/emesis center activated?
- Afferent fibers in the gut
- Chemoreceptors trigger zone
- Cerebral cortex
- Vestibular apparatus
What is the mechanism of action of scopolamine?
- Blocks acetylcholine at parasympathetic sites (smooth muscle, secretory glands, CNS)
- Reduces histamine and serotonin activity
What is the PK of scopolamine?
-SubQ or transdermal admin
-Change patch every 3 days
-Onset: 6-8hrs; duration 72hrs
-Hepatic metabolism
What are the side effects of scopolamine?
-Tachycardia, flushing, dry mouth, blurred vision, drowsiness, urinary retention, constipation, psychosis, hallucinations
*Similar to atropine
What are the special considerations for scopolamine?
Contraindicated in narrow-angle glaucoma or with other agents containing belladonna
What are the major interactions for scopolamine?
Anticholonergic agents
Other CNS depressants
SSRIs
Thiazides
What are the uses of Prochlorperazine (Compazine)?
N/V
What is the MOA of Prochlorperazine?
Antagonizes D2 receptors in the CTZ and gut, also blocks M1 and H1 receptors
What is the PK of Prochlorperazine?
- Oral or rectal admin
- Duration 3-4 hours oral, or 3-12 rectal
What antiemetic agents are associated with the side effect of tardive dyskinesia?
Prochlorperazine
Metoclopramide
What are the side effects of prochlorperazine?
Extrapyramidal effects, tardive dyskinesia, hypotension, long QT, CNS effects
What are the uses for metoclopramide?
- Chemotherapy-induced and post-op N/V
- Documented gastroparesis
- Off label: tx of hiccups and N/V of early pregnancy
What drug can be used off label for the treatment of hiccups in pregnancy as well as N/V?
Metoclopramide
What is the PK of metoclopramide?
Oral or IV admin
- Short duration of action, dosed 3-4 times per day
- CYP2D6
What are the two big side effects associated with metoclopramide?
Tardive dyskinesia and hyperprolactinemia
What are the indications of use for ondansetron (zofran)?
- Chemotherapy induced N/V, management of post-op N/V
- Effective when used alone and even more effecting when in combo with dexamethasone
What drug can be combined with ondansetron to improve efficacy?
Dexamethasone
What is the MOA of ondansetron?
Selectively blocks 5-HT3 receptors in the periphery and brain
What is the PK of ondansetron?
- Oral or IV admin
- Onset 30 min, peak 1-2 hours
- Extensively metabolized in the liver
- Dose adjust in hepatic impairment
What are the SE of ondansetron?
- HA, dizziness, confusion, SOB, constipation, Long QT***
Monitor EKG and watch for signs of serotonin syndrome
What are the indications of use for dronabinol?
- Second line for chemo-induced N/V
- Stimulate appetite in patients with AIDS
What medication can be used to stimulate appetite in patients with AIDS?
Dronabinol
What is the MOA of dronabinol?
Activates cannabinoid receptors
What is the PK of dronabinol?
Oral admin, onset in 30-60 minutes
Duration 4-6 hours
Hepatic metabolism
What are the SE assocaited with dronabinol?
Euphoria, CNS changes, abd pain, vomiting, flushing, hoptension, vertigo
What should be monitored while on dronabinol?
HR and BP, and cannibis hyperemesis
What are the contraindications for dronabinol?
Psych disorders and SUD
What are the indications of us for promethazine?
- reduce emesis ass with surgery, cancer chemo, and toxins
- widely used in children
- motion sickness
What antiemetic agent is widely used in children?
Promethazine
What is the MOA of promethazine?
Antihistamine –> blocks D2 receptors in the CTZ and blocks H1 receptors in the brainstem
What is the PK of promethazine?
- Oral, IM, or IV
- Duration 4-6 hours
- CYP metabolism
Are EKG changes associated with promethazine use?
Yes
What antiemetic agents are OCT to treat motion sickness?
Meclizine (Bonine)
Dimenhydrinate (Dramamine)
What is the MOA of Meclizine?
Blocks H1 and M1 receptors –> Depresses labyrinth excitability and vestibular stimulation
Meclizine should be avoided in what conditions?
Glaucoma, asthma, urinary retention, pyloric/duodenal obstruction
What antiemetic agent depresses labyrinth excitability and vestibular stimulation in the treatment of motion sickness?
Meclizine
What is the MOA of Dimenhydrinate (Dramamine)?
Blocks H1 receptors in peripheral sites and CTZ
Has anti-cholinergic effects
What is the PK of dimenhydrinate (dramamine)?
- Oral and IM admin
- Onset 30 minutes, duration 4-6 hours
- Hepatic metabolism
What are the side effects associated with dimenhydrinate?
Tachycardia, anorexia, epigastric distress, sedation, dizziness, xerostomia, blurred vision, SJS
What are the bulk-forming laxatives and what are the MOA?
Methylcellulose
Psyllium (Metamucil)
MOA: absorb and retain water in the intestine –> increase mass of stool, promotes peristalsis
Same effect as dietary fiber
What are the SE of bulk-forming laxitives?
- Systemic sx rare
- Esophageal obstruction possible if not swallowed with water
- Bloating, flatulence, GI distress
What patients is lactulose recommended?
Not commonly used, reserved for pts who do not respond to bulk-forming agents
What is the MOA of magnesium oxide (milk of magnesia)?
Saline-laxative, retains water in the intestines –> increases intraluminal pressure and promotes peristalsis
What is the gold standard osmotic laxative for colonoscopy preps?
Polythyleneglycol-PEG (MiraLAX)
What is a major drug interaction with Polythyleneglycol-PEG?
Digoxin
What laxatives can be used in opioid induced constipation?
Nalaxegol
Methylnaltrexone
Lubiprostone
