Pharmacology Third Year

1. Drug affecting
MOTILITY of
GIT

2. Antiemetic agentsAntiemetic agents

3. Antiemetic agents
• Antiemetics are drugs given to prevent or releive
nausea and vomiting
• They exert their effects on the vomiting center, the
cereberal cortex, the CTZ, or the vestibular appratus
• The neurotrasmitters involved in controlling or
preventing nausea and vomiting include dopamine,
acetylcholine, histamine and serotonin

4. Antiemetic drugsAntiemetic drugs
H 1 antagonists: Meclizine, Diphenhydramine,
Dimenhydrinate
Muscarinic receptor antagonists: Hyoscine.
Dopamine antagonists:
-Phenothiazines e.g. chlorpromazine
-Butyrophenones e.g. Haloperidol.
-Metoclopramide (prokinetic)
-Domperidone (prokinetic)
5HT3 antagonists e.g. Ondansetron (Zofran) Effective in vomitting
due to anti-cancer chemotherapy)
Corticosteroids: (dexamethazone)

5. Metoclopramide (Reglan)Metoclopramide (Reglan)
It blocks central dopaminergic D2- receptors and
in high doses it blocks 5-HT3 receptors
It has antiemetic action
It accelerate gastric emptying (prokinetic)
It raise lower esophageal sphincter pressure
It increase intestinal peristalsis

6. MetoclopramideMetoclopramide
Indications
 Vomiting due to anesthesia, uremia, drugs
Rapid emptying of stomach before emergency
surgery and labour
 Gastro esophageal reflux and esophagitis.
GIT investigation: e.g. endoscopy

7. MetoclopramideMetoclopramide
Side effects
- Sedation, diarrhea .
- Involuntary movements e.g parkinsonism
- Hyperprolactinemia .
DOMPERIDONE (MOTILIUM)
Similar to Metoclopramide with less CNS effects
and does not cross BBB

8. Choice of anti-emeticsChoice of anti-emetics

9. EmeticsEmetics
Agents that induced reflex vomiting e.g. syrup
ipecac, apomorphine and hypertonic salt
solution.
Uses : Useful for removing unabsorbed toxin
from the stomach

10. Prokinetics drugsProkinetics drugs
Drugs that promote gastrointestinal motility
without purgation

11. Cisapride (prepulsid)
• It releases acetylcholine from
cholinergic neurons in the enteric
nervous system and mesenteric plexus.
• It hastens esophageal clearance and
raise lower esophageal sphincter
pressure.
• Uses
• Gastro esophageal reflux

12. Anti-spasmodicAnti-spasmodic
librax (Clidinium plus chordiazepoxide )

13. Anti-cholinergic drugs
Hyoscine-N-butyl bromide
Competitively block muscarinic M3 receptors in GI
Decrease peristalsis & constrict sphincters
Adverse effects:
Dry mouth, constipation, tachycardia, palpitation, raised IOP
& urine retention
Caution: elderly patients (glaucoma) & male patients
(prostatic hypertrophy)

14. LaxativesLaxatives
A laxative induces defecation and is used in the
prevention and treatment of constipation
Constipation is best prevented with high fiber diet,
adequate fluid intake & regular exercise
Over use of laxative may lead to laxative habit or
dependence
Indications of laxatives:
1- Constipation
2- Hepatocellular failure (Magnesium sulphate,
lactulose).
3- To prepare the bowel prior to X-ray on GIT and
proctoscopic or colonoscopic procedures
4- To hasten excretion of poisonous substances in the
alimentary tract.

15. Laxatives ClassificationLaxatives Classification
Dioctyl, Liquid paraffin and
Glycerin suppository

16. Bulk laxativesBulk laxatives
dietary fibers (fruits and vegetables) Methyl
cellulose, bran and agar.
they are non- digestible and have capacity to
retain water in gut lumen thus enhance the bulk
and moisture content to stool
May cause intestinal obstruction, take sufficient
water to prevent obstruction

17. Osmotic laxativesOsmotic laxatives
Lactulose
Synthetic disaccaride , non digestable and
not absorbed in the small intestine
In the colon it retain water in lumen by
osmosis causing distension and reflex increase
in peristalsis
uses Constipation
hepatic encephalopathy

18. Irritant or stimulant laxativesIrritant or stimulant laxatives
Castor oil
•Very irritating to the gut, converted to recinoleic acid that
promptly increases peristalsis.
•Rapid strong complete evacuation of colon
•Uses: preparation of the patient for radiological
examination
Bisacodyl
Stimulation of peristalsis
Act on the large intestine producing a semi fluid stool
Side effects: Stimulant laxatives may cause diarrhea,
dehydration and electrolyte impalance, megacolon ,ulcerative
colitis, ↑ menstrual blood flow and abortion.
abdominal cramps and the potential for atonic colon with
prolonged use
Avoid in intestinal obstruction & pregnancy

19. Stool softenersStool softeners
Dioctyl
Softens of stool mass by lowering surface tension of stool to enter
more readily and softens the faces
Liquid paraffin: (physical and lubricant agent).
•It coats intestine so decreasing water absorption
Adverse effects
•Infiltration in liver, leakage and accumulation in regional lymph
nodes
•Long term use causes deficiency of Vit. A, D, E & K ( fat soluble
vitamins)
Glycerin suppository
It is considered as stool softener. It acts osmotic agent promoting stool
evacuation
“

20. Drug therapy of diarrhea

21. Treatment of diarrheaTreatment of diarrhea

22. Maintenance of fluid and
electrolytes balance
Maintenance of fluid and
electrolytes balance
• It is the first priority and many cases require
no other treatment.
• Dehydration is a common complication of diarrhoea
Balanced solution containing Na Cl + K Cl+
glucose + Na citrate is used as oral
rehydration solution For mild to moderate
dehydration
For sever dehydration:
IV fluids 5% dextrose & normal saline
KCl &/or Na HCO3, when hypokalemia &/or acidosis

23. Non-specific antidiarrhealNon-specific antidiarrheal

24. AdsorbentsAdsorbents
kaolin, pectin, active charcoal and bismuth
subsalicylate
these agents act by adsorbing intestinal toxins or
microorganisms and/or by coating or protecting the
intestinal mucosa.
Adverse effects:
Can cause constipation
They can interfere with the absorption of other drugs.

25. Opiates and opioid containing
preparation
Opiates and opioid containing
preparation
Diphenoxylate and Loperamide
Action:
have opioid-like actions on the gut, activating presynaptic
opioid receptors in the enteric nervous system to inhibit
acetylcholine release and decrease peristalsis.
Side effects include drowsiness, abdominal cramps, and
dizziness