The document summarizes various preclinical models used to screen emetic and anti-emetic drugs. It describes in vivo models using animals like dogs, ferrets and house musk shrews to induce vomiting through chemicals like cisplatin, copper sulfate, apomorphine and radiation. It also discusses in vitro models to test 5-HT3 receptor antagonism and parameters observed like latency and number of vomiting episodes.

1. Seminar presentation on:
Preclinical screening method of
emetic and anti-emetic drugs
PRESENTED BY: SIRAJUDDIN MOLLA
1ST SEM, M.PHARM
DEPARTMENT OF PHARMACOLOGY
SPER, JAMIA HAMDARD

2. • INTRODUCTION
• PATHOGENESIS OF VOMITING
• CLASSIFICATION OF ANTI EMETIC DRUGS
• CHOICE OF ANIMALS AND EMETOGENS
• PARAMETERS OBSERVED
• INVIVO MODELS
• INVITRO MODELS
• HUMAN MODELS
CONTENTS

3.  NAUSEA:
• Nausea is an uneasiness of the stomach and non observable
subjective feeling that often accompanies the urge to vomit, but
doesn't always lead to vomiting.
 EMESIS: Vomiting or emesis is clinically defined as the oral eviction of
gastrointestinal contents, due to contractions of the gut and the
muscles of the thoracoabdominal wall.
• ACUTE EMESIS (occurs within minutes and resolves within 24 h)·
• DELAYED EMESIS (occurs after 2-3 days)
• BREAKTHROUGH EMESIS (emesis occurring after the prophylactic
antiemetic treatment)
INTRODUCTION

4.  RETCHING: It is a labored movement of abdominal
and thoracic muscles for attempting to vomit w/o
expulsion of vomitus (without bringing any food up
up from stomach).
 EJECTION: Expulsion of vomitus forcefully through
mouth and nose.
Contd…

5.  The fourth ventricle of the brain hosts the
vomiting centre called the chemoreceptor
trigger zone (CTZ). It is also called the area
postrema. When the CTZ is stimulated,
vomiting may occur.
 The CTZ contains receptors for dopamine,
serotonin, opioids, acetylcholine and the
neurotransmitter substance P.
 When stimulated, each of these receptors
gives rise to pathways leading to vomiting
and nausea.
HOW VOMITING IS OCCURE

6. Pharynx & GIT
(enterochromafin cell)
Release 5 HT3, Substance P
Chemoreceptor Trigger Zone
(CTZ)
(Outside BBB)
Dopamine D2
5 HT3
Opioid Receptors,
substance P
Cancer chemotherapy
(cytotoxic drug),
Opioids, digoxin, morphine
Cerebral cortex
Smell
Sight
Thought
Anticipatory emesis
Motion sickness
Vestibular nuclei
(in pons of brain stem)
Muscarinic
Histaminic H₁
Chemo & radio therapy
Gastroenteritis
Vestibular labyrinth
Drugs in blood
and CSF
Pathophysiology of Emesis
Vomiting Centre
(medulla oblongata)
Have receptors of
Muscarinic,
5 HT3, Histaminic H1,
substance P

7. Pathophysiology of Emesis
Vomiting Centre
(medulla oblongata)
Have receptors of
Muscarinic,
5 HT3, Histaminic H1,
substance P
 Relaxation of lower
oesophageal sphincter
 Contraction of
diaphragm and
abdominal muscle
vomitin
g
stimulus

8. CLASSIFICATION OF ANTIEMETICS
1 5HT3 antagonists
ondansetron, tropisetron,
palanosetron, granisetron
2
Centrally acting
dopamine receptor
antagonists
prochlorperazine,
chlorpromazine
3
H1 receptor antagonists Cyclizine, hydroxyzine,
promethazine, diphenhydramine
4 Muscarinic antagonists Scopolamine

9. 5 Proinetic agents Metoclopramide, Domperidone,
Cisapride, Mosapride
6 Neurokinin receptor
antagonists Aprepitent
7 Cannabinoid receptor
antagonists
Dronabinol, Nabilone
8
Corticosteroids and
NSAIDs Aspirine
9 Benzodiazepines Alprazolam, Diazepam
10
Phosphorated
carbohydrate solutions
Aqueous solutions of glucose,
fructose and phosphoric acid
Contd…

10. Pharynx & GIT
(enterochromafin cell)
Release 5 HT3, Substance P
Chemoreceptor Trigger Zone
(CTZ)
(Outside BBB)
Opioid Receptors
substance P
Dopamine D2
5 HT3
Cancer chemotherapy
(cytotoxic drug),
Opioids, digoxin, morphine
Cerebral cortex
Smell
Sight
Thought
Motion sickness
Vestibular nuclei
(in pons of brain stem)
Histaminic H₁, Muscarinic
Chemo & radio therapy
Gastroenteritis
Vestibular labyrinth
Drugs in blood
and CSF
Mechanism of action of antiemetic drugs
Vomiting Centre
(medulla oblongata)
Have receptors of
Muscarinic,
5 HT3, Histaminic H1,
substance P antihistaminic H₁
(promethazine)
5 HT3 Receptor
antagonists
(ondansetron)
D2 Receptor
antagonists
(chlorpromazine,
metaclopromide)
Muscarinic
Receptor
antagonists
(Scopolamine)

11. Commonly used
animals:
CHOICE OF ANIMALS
Dogs
Cats
Ferrets
Monkeys
House musk shrew (Suncus murinus)
Least shrew (Cryptotis parva) Gerbils
Pigeons

12. • DRUG INDUCED
• RADIATION STIMULUS
• MOTION STIMULUS
CHOICE OF EMETOGENS

13. • Behavioral changes
• Latency to first retching and vomiting.
• Number of vomiting episodes.
• Conditioned flavor avoidance (PICA) in
rats and mouse.
PARAMETERS ASSESSED

14. 1. Cisplatin-induced emesis model
2. Apomorphine-induced emesis model
3. CuSO4-induced emesis model
4. Methotrexate- induced emesis model
DRUG INDUCED EMESIS
MODELS

15. • Cisplatin causes Both Acute And Delayed
Emesis.
• Used as emetogen to evaluate acute emesis.
• Solvent: normal saline at 70°C followed by slow
cooling to 40°C
Cisplatin-induced emesis model

16. Assessment of emetic and
anti-emetic activity in
pigeons
 Emesis in pigeons can be induced by various agents.
 Formerly, the phenomenon has been used for
standardization of cardiac glycosides (Hanzlik 1929).
 More recently, dose response curves of emesis have been
determined for various agents and anti-emetic effects were
evaluated (Wolff and Leander 1994, 1995).
PURPOSE AND RATIONALE
Pigeons

17.  Male White Carneaux pigeons are planned to keep in individual
stainless steel cages at constant temperature and humidity.
 They are supposed to maintain at 90% of their free-feeding body
weights by once-daily feeding of approximately 20 g Purina Pigeon
Pigeon Checkers.
 All testing is to be conducted during the illuminates phase of the
light-dark cycle.
 On test days, the birds are to be fed 5 min before the start of an
emetic trial.
 If vomiting occurs, the pigeons are to be given an additional 20 g
of feed before being returned to their home cages at the
conclusion of the observation period.
 Individual subjects are to be allowed a recovery period of at least 3
PROCEDURE

18. For the following compounds emetic doses are reported:
 Cisplatin 10 mg/kg, injected into a wing vein.,
 Ipecac syrup, 1 to 3 ml/kg, administered via a feeding
passed through the crop to the opening of the
proventriculus.
 Emetine, 1 to 20 mg/kg, injected into the pectoralis
 m-(chlorphenyl)-biguanide (mCBG), 0.32 to 5 mg/kg,
injected intramuscularly,
 Ditolyganidine (DTG), 5.6 mg/kg, injected intramuscularly.
 Test substances with potential anti-emetic activity are to be
injected at various doses 15 min before the emetic
challenge.
 The animals are to be observed for vomiting during 2 h.
Contd…

19.  ED50 values for with 95% confidence limits are
calculated for the activity of emetic substances, as
well as for the inhibition of emesis by anti-emetic
drugs after a high dose of the emetic compound.
EVALUATION

20. • Apomorphine is an opiate that acts as a potent
central dopamine agonist directly at the area
prostrema via dopamine receptors.
• As the vestibular pathways are also involved in
apomorphine-induced emesis, the active animals
develop emesis readily than sedated and
immobile animals.
Apomorphine-induced
emesis model

21. • Dogs are most sensitive followed by ferret.
• Use of apomorphine in cats is controversial as
administration of apomorphine can cause excitation in
cats.
• Suncus murinus is unresponsive to apomorphine.
Contd…

22. Assessment of emetic and
anti-emetic activity in dogs
 Emesis comparable to man occurs only in a few animal species.
 Among laboratory animals, the dog is a suitable species to test anti-
emetic drugs.
 Apomorphine-induced emesis is also used to evaluate neuroleptic
drugs (chlorpromazine, Risperidone).
 Burkman (1982) described a technique relying upon the use of
apomorphine either as a reference standard against which other
emetics can be compared, or as a challenging agent against which anti-
emetic compounds can be evaluated.
PURPOSE AND RATIONALE
Dogs

23.  Beagle dogs weighing between 15 and 20 kg are planned to be used.
 Each dog is to be given 200 g food 30 min prior to an assay session.
 The threshold emetic dose of apomorphine hydrochloride is to be
established for each dog by administering single doses at 5 day
intervals in gradually increasing amounts.
 The starting dose being 0.07 mM/kg (22 mg/kg) body weight, i.m., and
and is to be subsequently increased (or decreased) as required.
 Injection sites are to be alternate between contralateral gluteus muscles.
PROCEDURE

24.  The threshold dose is defined as the concentration provoking an
emetic episode and determined for each individual animal.
 The threshold emetic dose is relatively stable for a given group of
dogs over a period of 2 months.
 Continued administration to the same dogs for longer periods of
time is inadvisable as Pavlovian emetic conditioning becomes
evident after 8–10 doses of apomorphine.
 Establishment of an emetic threshold for a test compound using
similar dosing schedule allows to quantitatively express the test
compound’s emetic potency as a ratio compared with the
standard.
Contd…

25.  Usually, 4–6 animals are sufficient to provide a reliable estimate of the
test compound’s emetic efficacy and potency.
 In the anti-emetic assay, dogs whose apomorphine threshold emetic
dose has been determined receive various concentrations of the
potential anti-emetic drug at a given time interval prior to
 The dose initially selected for the anti-emetic is a fraction of the acute
LD50 of this drug in mice.
 A new threshold dose is estimated in the presence of the test anti-
emetic and compared to the threshold dose in the presence of the
reference standard chlorpromazine.
Contd…

26. Using the threshold doses, the relative potency of an
emetic compared to apomorphine,
or the relative potency of an anti-emetic compared to
chlorpromazine, is calculated
EVALUATION

27. • Copper sulfate (CuSO4) Powerful oxidizing agent
and an irritant to mucosa membranes.
• If administered orally, it causes irritation of
gastric mucosa and leads to nausea and
vomiting.
• Solvent: Distilled water
Copper sulfate-induced
emesis model

28.  The ferret is a well established animal model of emesis which
responds to cancer chemotherapeutic agents in a manner similar
to that observed in man (Florczyk et al. 1982).
 The animals react with vomiting and retching after challenge with
central (loperamide and apomorphine), peripheral (CuSO4), or
mixed central and peripheral (ipecacuanha, cisplatin) emetic
stimuli.
 The model has been used to test the anti-emetic properties of 5-
HT3 receptor antagonists and tachykinin NK1 receptor
Anti-emetic activity in ferrets
PURPOSE AND RATIONALE

29.  Adult male ferrets weighing 1 to 1.5 kg are planned to be randomly
assigned to the different treatment groups.
 Each animal is to be anesthetized by inhalation with methoxyflurane.
A jugular vein is to be cannulated and exteriorized from the outside of
the neck.
 Following recovery from the anesthesia, the animals are to be dosed
with the test drug or the standard or the vehicle 30 min prior i.v.
administration of 10 mg/kg cisplatin.
 The numbers of retches and vomits occurring following the
administration of the emetogen are to be recorded in each animal for 5
h.
 Retching is defined as rhythmic inspiratory movements against a
PROCEDURE
Ferrets

30.  Duration of action of the compounds is to be assessed by
determining the period of time for which the inhibitory effects
remain significantly different from vehicle controls.
 Statistical analysis of the data is to be performed by a repeated
measure analysis of variance (ANOVA) followed by pairwise
comparisons against control at each time period using Fisher’s
LSD multiple comparison test
EVALUATION
Fisher's least significant difference (LSD) procedure is a two-step testing
procedure for pairwise comparisons of several treatment groups.

31. • Animals: Dogs, cats, ferrets & shrews.
• MTX is prepared by dissolving in 5% Dextrose.
• Test drug/vehicle is administered at 24, 36, 48 & 60h after MTX.
• Observed under video camera for 72h.
• Animals can be retested with MTX at least 6 weeks later
MTX-induced Delayed
emesis model

32. COMMONLY USED MODELS
• Cat model
• Suncus murinus model
• Rat model
Motion-induced
emesis model
Dogs are probably as sensitive to motion induced emesis as
man.

33. The house musk shrew (Suncus murinus) is a small
insectivore that has been shown to exhibits emesis when
exposed to linear reciprocation motion (Ueno et al. 1988;
Okada et al. 1994).
Activity against
motion-induced
emesis
PURPOSE AND RATIONALE
House musk shrew (Suncus murinus)

34.  Adult male (body weight range 55–90 g) and
female (body weight range 35–50 g) are used.
 The animals receive a dose of the test drug or
vehicle in a volume of 4 ml/kg 15 min before
motion testing.
 The animals are placed in a Perspex chamber
(11 cm wide × 22 cm long × 11 cm high) that is
attached to the platform of a shaker set to
execute a linear horizontal movement of 4 cm at
a frequency of 1 Hz along the long axis of the
chamber.
PROCEDURE

35. The animals are allowed approximately 3 min to become accustomed
to the chamber before exposure to motion for a period of 5 min,
during which the number and timing of emetic episodes are recorded.
An emetic episode usually consists of a short period of rapid retching
followed by a vomit.
A cross-over design is used for the experiment, with animals exposed
to motion testing following treatment with vehicle control on one
occasion, and following treatment with test drug on another.
An interval of 12 days is allowed between treatments.
Contd…

36.  Group results are expressed as mean ±SEM.
 Either Student’s t-test or the Wilcoxon
signed rank test is used as a measure of
significance.
EVALUATION

37.  Radiation induced emesis model
• Dog model
• Ferret model
• Rat model
 Ferrets are most sensitive to radiations followed by dogs.
 Cats are resistant to radiations.
Radiation-induced
emesis model

38. • Used to demonstrate the pharmacological activity
of newer anti-emetic agents.
• 5-HT3 are the most potent of all anti-emetics.
• The experimental drugs can be evaluated for 5-HT3
receptor antagonist activity using in vitro
In vitro models

39. Apomorphine, 0.05 mg/kg, SC is an appropriate challenge dose for
testing compounds for antiemetic activity in normal human volunteers.
Human Models
Apomorphine induced:
Healthy men are given single 5-minute infusions of ondansetron 30
minutes before oral administration of 30 ml syrup of ipecacuanha.
Emetic episodes and nausea are assessed over an 8-hour period.
Ipecac induced

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