21. Anti-Nauseants Flashcards
What causes nausea/vomiting (N/V)?
Bugs and drugs are 2 most common agreements
Bugs: food poisoning, often better to let it run its course and maintain hydration
E. coli is food poisoning that could be deadly
Drugs: chemotherapy induced N/V (CINV), chemotherapy agents target rapidly dividing cells (GI tract), also stimulate release of serotonin (5HT), 5HT stims N/V in CNS and increased peristalsis
Slides 5-7
What is emetogenic scales?
Scales that show which drugs are bad for vomiting and which are good
What is post operative N/V (PONV)?
Common post surgical complication
Occurs due to multiple factors, not just anesthetics
Slide 9
What are the 3 types of drugs that cause chemotherapy induced N/V?
Cholinergic agonists (cholinesterase inhibitors)- hurry up the GI tract, increase peristalsis
Dopaminergics- Parkinson’s
Opioids
What are the key areas mediating nausea/vomiting (N/V)?
Within BBB:
Emetic centre
Nucleus tractus solitarius (NTS)
If you’re vomiting, blame emetic centre in brain, NTS has multiple receptors on it that feed into the emetic centre and stim vomit
Outside the BBB:
Chemoreceptor trigger zone (CTZ)- feeds into NTS and emetic centre directly
5HT-3 and Muscarinic (M) receptors also in gut
Inner ear (motion) mediate motion sickness
Slide 10
What are the 6 sections of anti-nauseants?
H1 antagonists Anti-Muscarinics Serotonin antagonists Neurokinin-1 antagonists D2 antagonists Other
What are H1 antagonists?
One drug
Dimenhydrinate (Gravol)
Blocks receptors in the NTS and inner ear, inhibits stimulation of the emetic centre (useful for motion sickness)
Also has anti cholinergic effects (reduces peristalsis in GI tract)
Takes 30 mins to absorb
Side effects: drowsiness (sometime use gravol to help sleep), dry mouth (can cross BBB, so worry about ACh being blocked)
Oral, rectal, parenteral
Slides 12-17
What are muscarinic antagonists?
One drug
Scopolamine
Targets inner ear (motion), NTS, CTZ, reduce peristalsis in gut
Targets muscarinic receptors (they’re all over)
Patch used for motion sickness (patch can readily cross membranes
Slides 19-21
What are serotonin (5HT-3) antagonists?
One drug
Ondansetron
Serotonin receptors in gut, NTS, CTZ
Breakthrough drugs in treating CINV and PONV (big help for cancer treatment, can do chemotherapy longer with these drugs)
Side effects: constipation (related to reduced peristalsis)
Slides 23-26
What are neurokinin (NK)-1 antagonists?
One drug
Aprepitant
NK-1 receptors mediate N/V in both the emetic centre in the CNS and the CTZ
Blocking these receptors inhibits N/V
Most commonly used for CINV
Side effects: hiccups, anorexia (reduced appetite), fatigue
Slides 28-30
What are D2 antagonists?
2 drugs
Metoclopramide and domperidone
Once used more for reflux and motility issues, now lore for nausea
Inhibits the chemoreceptor trigger zone
Also used as prokinetics and are useful in treating GERD
increase lower esophageal sphincter tone (keeps acid from escaping into esophagus), increase contractions, gastric emptying (moves food out faster)
Domperidone doesn’t cross BBB so no movement disorders
Side effects: movement disorders, hyperprolactinemia (dopamine normally inhibits prolactin release)
Slides 32-36
What are the 3 other drugs used for nausea?
Corticosteroids
Cannabis- cannabinoid receptors are found throughout the CNS (and elsewhere)
Benzodiazepines- hypnotics, help us sleep, may help with the anxiety associated with N/V
Slide 38
How do you treat nausea in pregnancy?
3 drugs to use
N/V is associated with pregnancy (NVP)
Few drugs are safe to use
Pyridoxine- mechanism unknown (but it works)
Pyridoxine/doxylamine- doxylamine is an H1 antagonist (like dimenhydrinate)
Dimenhydrinate
