This document discusses drugs that induce vomiting (emetics) or prevent vomiting (antiemetics). It describes the mechanisms of vomiting and classifies various emetics such as apomorphine, mustard, and ipecacuanha. It also categorizes and explains examples of different types of antiemetics, including prokinetics like metoclopramide, antimuscarinics like hyoscine, antihistamines, neuroleptics, and 5-HT3 antagonists like ondansetron and granisetron. The document provides details on the mechanisms, dosages, and side effects of these selected emetic and antiemetic drugs.

1. PHARMACOLOGY
Presentation on:
Drug affecting gastrointestinal tract:
Emetics and antiemetics
Group 6
[pharmacy department]
By tujar kaso(b pharm)

2. Emetics
 emetics are drugs that produce or induce emesis/vomiting.
MECHANISM OF EMESIS/VOMITING
 emesis is the forceful expulsion of the contents of the stomach via
the mouth or sometimes through the nose.
 the vomiting reflex is stimulated by two centers in the medulla
vomiting center
 chemoreceptor trigger zone(CTZ)

3. Haw CTZ is stimulated?
 tactile stimulation of the back of the throat, a reflex to get
rid of something that is too big or too irritating to be
swallowed.
 excessive stomach distention.
Increase intercranial pressure by direct stimulation
Stimulation of the vestibular receptor in the inner ear
 intense pain fiber stimulation
 direct stimulation by varies chemicals, including fumes,
certain drugs, and debris from cellular death

4. Classification of emetics
1. STIMULANTS OF CTZ
A. apomorphine
B. morphine
2. IRRITANTS OF GASTRIC MUCOSA
A. Mustard
B. sodium chloride
3. BOTH CTZ STIMULANT AND IRRITANT EFFECT
A. ipecacuanha
B. digitalis

5. APOMORPHINE
 given through subcutaneously or through intramuscular -6mg
 causes vomiting within 15 min
 in hypertensive individual, however ,even a subtherapeutic dose may
elicit sever emesis and collapse
 vomiting is often accompanied by sedation
 it should not be used if respiration is depressed
 larger doses often produce restlessness, tremor, occasionally
convulsion
 sometimes may cause hypotension, syncope and coma

6. MUSTARD
 it is household remedy to induce vomiting
 volatile oil
 dose-1teaspoonful with water
 formed as a result of a reaction between a glycoside and an enzyme in the
presence of water
SODIUM CHLORIDE:
 given orally
Withdraw fluids from the cells lining the stomach thus causes irritation
which reflex emesis.

7. Ipecacuanha(Emetine)
 act by irritating gastric mucosa as well as through CTZ
 dried root of cephalis ipecacuanha contains emetine
 commonly available as syrup to induce emesis at a dose of:
 adults-15-20ml
 children- 10-15ml
 infant-5ml
 takes 15 min or more for the effect.

8. Emetics-contraindication
 ALL EMETICS CONTRAINDICATED IN:
 corrosive(alkali, acid) poisoning
 CNS stimulant drug poisoning
 kerosine(petroleum) poisoning
 unconscious patient

9. Antiemetics
 antiemetics are drugs that can prevent vomiting/emesis.

10. CLASSIFICATION
1. prokinetics
A. metochlorpramide
B. domperidone
2. antimuscarinic
A. hyoscine
B. meclozine
3. antihistamine
A. cyclizine
B. promethazine(Phenergan)

11. 4. Neuroleptics
A. Cyclizine
B. Promethazine(Phenergan)
5. 5-HT3 antagonists
A. Ondansetron
B. granicetron

12. prokinetics
 these drugs which promote gastrointestinal motility and quicken
gastric emptying
drug available:
metochlorpramide
 domperidone
mechanism of action of prokinetic drug
 D2 antagonist
 5-HT4 agonism
5HT3 antagonism

13. metoclopramide
 introduced in early 1970s as a “gastric hurrying agent”
 widely used antiemetic
 it has both central and peripheral effect:
 central-block the dopaminergic receptor
 peripheral- increased gastric emptying at a dose of-5-
10mg

14. Interaction:
 hastens absorption of many drugs:
Aspirin
 diazepam etc. facilitate the gastric emptying
 reduced absorption of digoxin
adverse effect:
sedations, dizziness, diarrhea, muscle dystonia
 long term use can cause parkinsonism, galactorrhea and
gynecomastia

15. domperidone
 D2 antagonist
 chemically related to haloperidol but pharmacologically related to
metoclopramide
 has lower ceiling antiemetic and prokinetic action
 poorly crosses BBB
 rare extra pyramidal side effect
 given with lavodo or bromocriptine to counteract their dose limiting
emetic action
 absorbed orally, but bioavailability is only 15% due to first pass
metabolism

16.  completely metabolized and excreted in urine
 t1/2 I 7.5hr
 side effect are less than with metoclopramide:
dry mouth
 loose stool
 headache
 rashes
 galactorrhea
 cardiac arrhythmias on rapid I.V injection

17. ANTIMUSCARINIC
 competitively inhibit action of acetylcholine at muscarinic receptor
hyoscine:
 most effective in controlling motion sickness
 0.2-0.4 mg oral, I.M
 brief duration of action
 transdermal patch 1.5mg applied behind thee pinna to be delivered
over 3 days-suppresses motion sickness while producing only mild
side effect

18. Neuroleptics
 they act by suppressing the CTZ so they antagonize vomiting
produced by drug which stimulate CTZ.
 act by block d1 receptors in the CTZ
 antiemetic dose is much lower than antipsychotic doses
 these agents should not be administered until the cause of vomiting
has been diagnosed

19.  broad spectrum antiemetic, effective in:
 drug induced and post anesthetic nausea and vomiting
 disease induced vomiting
 chemotherapy induced
 morning sickness: should not be used except in
hyperemesis gravidarum

20. 5-HT3 Antagonists
 (5-HT3) receptor antagonists block the vomiting reflex by inhibiting
5-HT3 receptors in the vomiting center, the chemoreceptor trigger
zone and in the small intestine.
 high first pass metabolism
Excreted by the liver and kidney
 given once or twice daily-orally or intravenously.
 even though 5 HT3 receptors are present in vomiting center and CTZ,
the antiemetic action is restricted to emesis caused by vagal
stimulation.

21. Granicetron
 it is 10 to 15 times more potent than ondansetron
 more effective in chemotherapy
 dose- iv 1mg
Ondansetron(emeset):
 block 5 HT3 receptors in GIT and CTZ
 specially used in the chemotherapy,
 dose- 4mg in each ampule, 4,8 mg tablet

22. Antihistamine
 they act by sedating the vomiting center
 they are safer for long term use
 effective in motion sickness and vomiting due to labyrinthine
disorder
 all antimotion drugs are more effective when taken ½-1 hr. before
commencing journey
 once sickness has started, it is more difficult to control