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Antiemetics

DR.dr.Asep Sukohar, M.Kes

Department of Pharmacology, Faculty Of Medicine,Lampung University

Asep Sukohar

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Asep Sukohar

Vomiting Centre(medulla)

Cerebral cortex

Anticipatory emesis

Smell

Sight

Thought

Vestibular

nucleiMotionsickness

Pharynx & GIT

Chemo & radio therapyGastroenteritis

Chemoreceptor

Trigger Zone(CTZ)

(Outside BBB)

Cancer chemotherapy

Opioids

Muscarinic, 5 HT3&

Histaminic H1

5 HT3 receptors

Dopamine D2

5 HT3,

,OpioidReceptors

Muscarinic

Histaminic H1

Pathophysiology of Emesis

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Asep Sukohar

Now answer this question

Which group of drugs can be used as antiemetics ?

Serotonin 5 HT3AntagonistsDopamine D2Antagonist

Anticholinergics

H1Antihistaminics

Cannabinoids

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Serotonin 5 HT3Antagonist

Potent antiemetics

Even though 5 HT3receptors are present in

vomiting centre & CTZ, the antiemetic action is

restricted to emesis caused by vagal stimulation.

High first pass metabolism

Excreted by liver & kidney

No dose reduction in renal insufficiency but neededin hepatic insufficiency

Given once or twice dailyorally or intravenously.

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Drugs Available

Ondansetron 32 mg / day

Granisetron 10 mg / kg / day

Dolasetron 1.8 mg / kg / day

Indications

Chemotherapy induced nausea & vomitinggiven

30 min. before chemotherapy.

Postoperative & postradiation nausea & vomiting

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Adverse Effects

Excellent safety profile

Headache & constipation

All three drugs cause prolongation of QT interval,

but more pronounced with dolasetron.

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Now answer this question

Which is a better antiemeticMetoclopramide orDomperidone ?

As CTZ is outside BBB both have antiemetic

effects.

But as metoclopramide crosses BBB it has

adverse effects like extrapyramidal side effects..

Domperidone is well tolerated.

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Phenothiazines &Butyrophenones

Phenothiazines

Prochlorperazine

Promethazine

Phenothiazines are antipsychotics with potentantiemetic property due to D2antagonism.

Butyrophenone

Droperidol

Droperidol used for postop. nausea & vomiting,

but cause QT prolongation.

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H1Antihistaminics

Most effective drugs for motion sickness

Drugs available

Meclizine

Cyclizine

Dimenhydrinate

Diphenydramine

PromethazineUsed in pregnancy, used by

NASA for space motion sickness

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Anticholinergics

Scopolamine (hyoscine)used as transdermal

patch for motion sickness

Cannabinoids

Dronabinolused as adjuvant in chemotherapy

induced vomiting.It is a psychoactive substance

Nabilone

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Now answer this question

A physician prescribed Tab.Ondansetron

for prophylaxis of motion sickness. Even

though ondansetron is a potent antiemeticit didnt produce any effect in this patient.

Can you explain why ?

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Explanation :

Vestibular nuclei has only

muscarinic and H1histaminic receptors.

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Asep SukoharGG 1007

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Asep SukoharGG 1008

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