Antiemetics are drugs that prevent nausea and vomiting. They work by blocking receptors in the vomiting center of the brain such as H1 receptors, muscarinic receptors, dopamine D2 receptors, and 5-HT3 receptors. Common antiemetics include antihistamines like cyclizine for motion sickness, scopolamine for motion sickness, phenothiazines like prochlorperazine for chemotherapy induced vomiting, and 5-HT3 receptor antagonists like ondansetron for chemotherapy and radiation induced vomiting. The document discusses the mechanisms and uses of various classes of antiemetic drugs for conditions like morning sickness, motion sickness, vertigo, and vomiting caused by chemotherapy, radiation, or other illnesses.

3. DEFENITION
CLASSIFICATION
INDIVIDUAL DRUGS
ANTIEMETIC THERAPY IN SPECIAL
CASES
CLINICAL USES
SUMMARY

4. DRUGS THAT PREVENTS NAUSEA AND
VOMITNG ARE CALLED ANTIEMETICS.
VARIOUS DRUGS INCLUDING SOME
ANTIHISTAMINE AND
ANTICHOLINERGICS HAVE THIS EFFECT.
THEY ARE USED FOR CONDITIONS LIKE
MOTION SICKNESS, RADIATION OR
CHEMOTHERAPY INDUCED VOMITING,
MIGRAINE AND VERTIGO.

5.  Afferent inputs to VC are through CTZ
located in area postrema
 Emetogenic signals reach VC through
CTZ which is rich in dopamine D2
seratonin 5HT3, muscarinic and histamine
receptors which causes vomitting
 Drugs blocking these receptors are the
potential targets

6. A. Muscarinic receptor
antagonists/ antimuscarinic
agents.
Hyoscine(scopolamine)
Dicyclomine

7. Promethazine
Cyclizine
Cinnarizine
Dimenhydrinate
Diphenhydramine
……………………….3D
Doxylamine
These H1 receptor antagonists may act by

8. Non selective D1 & D2
antagonists
1. Phenothiazines :
Chlorpromazine,
Prochlorperazine.
2. Butyrophenone :
Haloperidol & Droperidol.

9. Ondansetron
Granisetron
Palanoseteron- most potent
Tropisetron
 Oral & Parental preparation are
available for use.


10.  Cannabinoids
 Benzodiazipines
 Pyridoxine (Vit B6) serves as cofactor
for the enzyme glutamate
decarboxylase which in turn increases
synthesis of GABA
 Glucocorticoids
Prokinetic drugs are
Metoclopramide,
Domperidone, Cisapride
Mozapride& Tegaserod.

11. MECHANISM OF ACTIONMECHANISM OF ACTION

13. Most effective drug for motion
sickness.
Action: Probably by blocking
conduction of nerve impulses across
a cholinergic link in the pathway
leading from vestibular apparatus to
vomiting center & is not effective in
vomiting of other etiologies.
Suitable for short brisk journeys & has

14. Treatment: Transedermal patches
containing Hyoscine , to be delivered
over 3 days has been developed,
applied behind the pinna. It
suppreses motion sickness whiele
producing only mild side effects.
Dose: 0.2-0.4 mg oral, i.m.

15. Uses: For prophylaxis of motion
sickness and for morning sickness.
It has been cleared of teratogenic
potential.
Dose: 10-20mg oral.

16. Action: Affords protection of motion
sickness for 4-6hrs, but produce
sedation & dryness of mouth.
Uses: By their central anticholinergic
action, they block the extrapyramidal
side effects of Metoclopramide while
supplementing its antiemetic action.
Their combination is used in
chemotherapy induced vomiting.

17. Promethazine is the first generation
of H1 receptor antagonist used as
antihistamine antiemetic.
Drugs: Phenargan, Promethagan.
Indications: Sedative, Antiallergic,
Adjunct in Motion sickness, Morning
sickness.
Side effects: Respiratory
depression, Seizures, Neuroleptic

18. Action: It is a sedative
antihistaminic with prominent
anticholinergic activity.
Uses: Morning sickness.
Side effects: Drowsiness, dry
mouth, vertigo & abdominal upsets.
Drugs: Doxinate – 10mg with
Pyridoxine 10mg tab.
Dose: 10-20mg at bed time; if
needed additional doses may be

19. Cyclizine is a Antihistamine
used to treat nausea, vomitting,
motion sickness & vertigo.
Action: These are less sedative
& less anticholinergic.
Contraindications: Glaucoma,
Prostatic hypertrophy, strong
Psychoactive effects.
Side effects: Drowsiness,
Xerostomia.

20. It is an antihistamine drug
Meclizine is long-acting ; protects
against sea sickness for nearly
24hrs.
Use: prevents nausea, vomiting,
motion sickness and also to
relieve allergic reaction.

21. It is an Anti vertigo or Antihistaminic drug,
& also protective for motion sickness
causing nausea & vomiting.
Action: Probably by inhibiting influx of
Ca2+ from endolymph into the vestibular
sensory cells which mediates labyrinthine
reflexes.
Contraindications: acute & chronic
parkinsonism, drowsiness & blurred
vision.

22. It is a dopamine receptor antagonist
used for treatment of nausea &
vertigo.
It is also a highly potent typical
antipsychotic & more potent than
chlorpromazine.
Uses: Treat Migrane headaches, as
an Anti-psychotic & alleviates
labrynthitis.

23.  It is a prokinetic drug that promotes
g.i. transit & gastric emptying.
 Action: on the GIT & CNS through D2
& 5-HT antagonism & 5-HT4 agonism.
 Adverse Effects: Sedation
,Dizziness, Loose stool, Muscle
dystonia, Galactorrhoea &
Gynacomastia.
 Uses: Antiemetic, Gastrokinetic,
Dyspepsia & Gastoesophageal reflux
disease.

24. It is a D2 antagonist, related chemically to
Haloperidol & pharmacologically to
Metoclopramide.
It crosses BBB very poorly, hence does
not affect the CTZ.
Its prokinetic action is based on D2
antagonism in the upper g.i.t.
Side Effects: Dry mouth, Loose stool,
Headache, Rashes, Galactorrhoea.
Drug & Dose: Domstal tab, 10mg, liq.
1mg/ml

25. It is a gastro prokinetic drug, which
increases motility in upper g.i.t.
Action: promotes Ach release
through 5-HT4 agonists so there is
increased G.I motility
Side Effects: mainly
Antidopaminergic side effects also
Dizziness & increased serum
transaminase.
Drug & Dose: Ciza 20mg tab,

26. Newer congener of cizapride with
similar gastro kinetic actions.
Side Effects : Diarrhoea, Dizziness,
abdominal cramps & Antidopaminergic
side effects.
Drug & Dosage: Moza 5mg TDS,
Normagut 2.5mg.

27. It is a prototype developed to
control cancer chemotherapy or
radiotherapy induced vomiting.
Action: Reduces the activity of
vagus nerve which deactivates the
vomiting center & also blocks the
action of 5-HT3.
Uses: prevents Chemotherapy,

28. Side Effects: Constipation, Dizziness,
Headache.
Clinical Use: CIV, Parkinson’s
disease, Alcoholism
Drug & Dosage: Emeset, tab. 4mg,
8mg, inj. 2mg/ml.

29. Vomiting associated with
pregnancy: Antiemetic drug therapy
may not be required for early
pregnancy vomiting (morning
sickness). If excessive Promethazine
is used, Pyridoxine supplement is not
required. However, in hyperemesis
gravidum, Pyridoxine supplement
along with doxylamine may be
required.

30. Motion sickness: Antihistamines
(Meclizine, Cyclizine) Hyoscine,
Promethazine.
Vertigo & other Labyrinthine
disorders: Hyoscine
Antihistamines, Phenothiazines.
Emesis due to Cytotoxic
agents: Odansetron,
Metoclopramide. In refractory cases
Nabilone, Dexamethasone are used.

31. SUMMARYSUMMARY

32.  Histamine H1 – receptor antagonist
-Cyclizine: motion sickness
Hyoscine: motion sickness
-Cinnarizine: vestibular disorders
(eg. Menieres disease) & motion
sickness
-Promethazine : severe morning
sickness of pregnancy (but if only
absolutely essential)

33. Muscarinic receptor antagonists -
Dopamine D2-receptor
antagonists
-Phenothiazines(eg.
Prochlorperazine) : vomiting
caused by uraemia , radiation, viral
gastroenteritis: severe morning
sickness of pregnancy( but if only
absolutely essential)
-Metaclopramide: vomiting
uremia , radiation, gastrointestinal
disorders , cytotoxic drugs.

34. 5- Hydroxytryptamine 5HT3- receptor
antagonists (eg. Odansetron):
vomiting caused by cytotoxic
anticancer drugs ; postoperative
vomiting , radiation induced vomiting.
Cannabinoids(eg. Nabilone) for
vomiting caused by anticancer drugs.

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