Anti-emetic drugs
Vomiting
Vomiting is the expulsion of gastric contents through the mouth
It is often preceded by nausea
Vomiting can be a valuable, life-saving physiological response (toxins, alcohol)
Severe vomiting may cause dehydration, acid-base imbalance, electrolyte depletion and aspiration
pneumonia
Causes of nausea and vomiting
Drugs - Cancer
chemotherapy- Opiates- Radiation, general anesthesia
Vestibular disorders: motion sickness
Endocrine causes: pregnancy
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food intolerance
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viral & bacterial infection
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disturbances of the middle ear (equilibrium)
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severe pain
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shock
 Control of Vomiting Reflex
 2 centers play imp. role in the vomiting reflex
 The chemoreceptor trigger zone (CTZ) is outside BBB respond directly to chemical stimuli in
blood and cerebrospinal fluid.

The vomiting center (VC) in the medulla – receives inputs from several sources (?)and
coordinates the motor mechanisms of vomiting
Chemical transmitters & receptors involved in vomiting
 Histamine (H1 )
 Ach (muscarinic)
 Dopamine (D2 )
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 5-hydroxytryptamine ( 5-HT3)
Antiemetic drugs
1- Anti-muscarinic drugs
2- Anti-histaminics (H1)
3- Dopamine (D2) antagonists
4-Serotonin (5 HT3) antagonists
5- Cannabinoids
6- Corticosteroids
Anti-muscarinic Drugs
 Receptors found in VC and vestibular N
 Anticholinergic drugs that can cross the BBB, will act directly on the vomiting center and have
anti-emetic properties
 This is the oldest group of drugs used to treat N & V, although this was not their original
intention
 Example: Scopalamine
 Routes of administration of Scopolamine
 Advantage of transdermal drug delivery
 Provides a controlled release of the drug into the patient
 Lower incidence of adverse effects
 Produces relief for 72 hours
 Adverse Effects
Anti-histaminic H1Drugs
Dimenhydrinate , Meclizine , Cyclizine
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Side effects
 occur with 1st generation antihistaminic
 Antimuscarinic : sedation, dizziness, confusion, dry mouth, blurring of vision , urinary retention
5-HT3Receptor Blockers
Mechanism of action:
They block 5-HT3 receptors:
1- Peripherally in upper GIT
2- Centrally in the vomiting center and CTZ
 Ondansetron (Zofran)
 Granisetron
 They caue Headache & dizziness ,Diarrhea
A physician prescribed Ondansetron Tab. for prophylaxis of motion sickness. Even though
ondansetron is a potent antiemetic it didn’t produce any effect in this patient. Can you explain why ?
 Vestibular nuclei has only muscarinic and H1 histaminic receptors
• Dopamine D2 Receptor Blockers ( D2 antagonists )

Benzamides

Phenothiazines :prochlorperazine

Butyrophenones : Droperidol
 Benzamides
 Antagonize D2 receptors in CTZ, periphery
 Metoclopramide (Primperan)
 Domperidone (Motilium)
 Treatment of vomiting induced by chemotherapy, radiation, opiates
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 Which is a better antiemetic– Metoclopramide or Domperidone ??????????????
 Metoclopramide: Adverse effects
Extrapyramidal effects, Tardive dyskinesia , Parkinsonian-like symptoms

Tardive dyskinesia
 Repetitive, involuntary, purposeless movements (usually involve the face) like tongue
protrusion, lip smacking, and rapid eye blinking. It occurs with chronic treatment (months to
years) and may be irreversible
 Cannabinoids
 Active ingredient in marijuana.
 Used in severe N & V due to cancer chemotherapy
 Nabilone & Dronabinol
 May act by inhibiting the vomiting center but the mechanism is unclear
 Adverse effects include:
Euphoria , dysphoria, hallucinations
Corticosteroids
Dexamethasone (Decadron)
Uses: to augment the antiemetic effect of 5HT3 receptor antagonists like
“ondansetron” in the treatment of chemotherapy-induced vomiting (brain
tumors) to counteract the development of edema, which may compress other
brain structures.
 Benzodiazepines
 Lorazepam, alprazolam
 Sedative , anxiolytic, amnestic properties
 Rx of N & V of Pregnancy
 The use of antiemetics during the 1st trimester of pregnancy  possible teratogenic effect
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 Non-pharmacologic interventions
 eat smaller meals more frequently, eat blander foods
 avoid spicy, fatty, or strongly odorous foods
 Taking prenatal vitamins at bedtime and suspending iron therapy
 Rx of N & V of Pregnancy
 Pyridoxine (vitamin B6 )
 is a water-soluble B-complex vitamin and is a necessary coenzyme in the metabolism of lipids,
carbohydrates, and amino acids.
 Dimenhydrinate
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