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Antiemetic CNS drugs


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What are the mechanisms of nausea?
1. Stimulation of stretch R or chemosensitive afferent vagal (stomach/upperGI) in hypomotility synd.
2. Direct stimul. of area postrema (chemotrigger zone): rich in Musc, Nico, Opiate and Dopamingergic R-->nucleus of solitary tract
3. Stim. vestibular afferents
4. higher cortical centers (conditioned responses)
What are the general rules of anti-emetics?
1. Drugs for motion sickness not work for drug-induced nausea x promethazine (phenergan)
2. Agent good at motion sickness (anticholinergics) also work for vertigo.
What are the agents for motion sickeness?
1. Pure Muscarinic Antag= Scopolamine
2. Mix H1/muscarinic Antag= dimenhydrinate (dramamine); hydroxyzine; promethazine; meclizine; diphenhydramine
What are the SE of motion sicknes drugs?
sedation and some anticholinergic i.e. dry mouth
What is the selective 5-HT3 antag drug?
What is Ondansetron used for?
1st line tx of post-op nausea induced by opiates and cancerchemotherapeutic agents.

***Not work for motion or GI stasis
How is Ondansetron used?
1. Alone
2. Combo: dexamethasone, lorazepam
What is metoclopramide?
(reglan) pro-kinetic
**Site of action: area postrema and NTS +vagal afferents
What are the extrapyramidal symptoms of Metoclopramide?
High doses: akathisia and dystonic reactions
What is metoclopramide used for?
1. Gastric stasis disorders
2. antiemetic to tx nausea from mildly emetic drugs
What is Chlorpromazine and prochlorperazine?
Neuroleptic phenothizine=
DA receptor antagonist
act at Area Postrema
What are Chlorpromazine and prochlorperazine used for?
1.relief of post-op nausea,
2. vomiting from radiation,
drugs with low emetogenic activity (opiates/cytotoxic agents)
3. 3rd line agent from cancer tx--"rescue therapy"

***low dose compared to tx of psychosis
What is dexamethasone and what is it used for?
Glucocorticoid--many uses; but enhances effectiveness of other antiemetics in CA pts.
What is lorazepam used for with anti-emetics?
Adjunct for cancer chemotherapy. Pretx with BDZ reduces stress and anticipatory emesis
What drugs would you use for GI irritation?
What drugs do you use for Motion Sickness?
Scopolamine (pure anti-musc)
or anti h1/anti musc (multi)
What do you use for severe pain induced nausea?
opiates--careful can cause nausea
What do you use for nausea caused by cardiac glycoside?
reduce dose of med
What do you use for nausea caused by SSRIs?
adjust does, give ondasetron
What for CA chemo nausea?
Ondansetron + dexamethasone
What give for post-op nausea?
What do you give for nausea caused by migraine?
What do you give for nausea in pregnancy?
avoid drugs b/c of teratogenic effect
*think may give phenergan?

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