Ondansetron Class • Seratonin ( 5-HT3) antagonist. Uses 1. The management of nausea and vomiting induced by chemotherapy and radiotherapy . 2. In the prevention and treatment of PONV Main action • Antiemetic.

1. Antiemetic's
Mr. Harshad Khade
MSc. Medical Technology (OTA)
Symbiosis International University, Pune.

2. Ondansetron Prochlorperazine Metoclopramide Cyclizine

3. Ondansetron
Class
• Seratonin ( 5-HT3) antagonist.
Uses
1.The management of nausea and vomiting induced by chemotherapy and
radiotherapy .
2. In the prevention and treatment of PONV
Main action
• Antiemetic.

4. Presentation
• As a clear, colourless aqueous solution in 2/4 ml ampoules
• containing 2 mg/ml ondansetron hydrochloride dihydrate.
• It is also available as 4/8 mg tablets,
• as a strawberry-flavoured lyophilizate (4/8 mg), and
• as a suppository containing 16 mg of ondansetron.
Mode of action
• Ondansetron is a highly selective antagonist at 5HT3 receptors and acts
both centrally and peripherally.
• Emetogenic stimuli appear to cause release of 5HT in the small intestine
and initiate a vomiting reflex by activating vagal afferents via 5HT3
receptors; ondansetron blocks the initiation of this reflex.
• Activation of vagal afferents may also result in the release of 5HT in the
area postrema, promoting emesis via a central mechanism.

5. Routes of administration/doses
• For prevention of chemotherapyor radiotherapy-induced nausea and
vomiting, the route of administration and dose of ondansetron should be
flexible in the range of 8–32 mg/day.
• For prophylaxis against PONV, the drug may be administered as a single
dose of 4 mg by intramuscular or slow intravenous injection.
• The paediatric dose is 0.1 mg/kg.
• Identical doses are recommended for treatment of established PONV.
Onset Less than 30 minutes
Duration 9 hours
Elimination Hepatic (95%

6. Effects
• CNS Headache
• RS
• The drug has no effect on the ventilatory response to CO2 .
• CVS
• May cause cardiac rhythm or ECG changes by prolongation of the QT
interval.
• GI Constipation, elevation of liver enzymes.
• Misc.
• Elimination of ondansetron is prolonged when given with other drugs
metabolized by cytochrome P450 system.

7. Prochlorperazine
Uses
1. Nausea and vomiting
2.Vertigo
3. Psychotic states, including mania and schizophrenia, and
4. In premedication.
Main actions antiemetic.

8. Presentation
• As tablets containing 3/5/25 mg, suppositories containing 5/25 mg,
• As a clear, colourless solution for injection containing 12.5 mg/ml of
prochlorperazine maleate, and
• As a syrup containing 1 mg/ml of prochlorperazine mesilate.
Mode of action
• The antiemetic and neuroleptic effects of the drug appear to be mediated
by central dopaminergic (d2) blockade,
• Leading to an increased threshold for vomiting at the chemoreceptor
trigger zone; in higher doses, prochlorperazine appears to have an
inhibitory effect at the vomiting centre.

9. Routes of administration/doses
• The adult dose is 5–20 mg 8 to 12 hourly, and
• the corresponding intramuscular dose is 12.5 mg 6-hourly
Onset 10-20 minutes
Duration 3-4 hours
Elimination Enterohepatic
Effects
• Prochlorperazine has anticholinergic properties which are additive to the
anticholinergic effects of other drugs.
• As a phenothiazine, it also has the potential to cause extrapyramidal
symptoms.

10. • CNS
• Sedative effects which are additive to other-hypnotics> May cause extra-
pyramidal syndromes (motor restlessness, oculogyric crisis, opisthotonus,
dystonias),especially in young male patients.
• RS The drug may cause mild respiratory depression.
• CVS
• Hypotension caused by #-adrenergic blocking effect. May potentiate
hypotensive effect of vasodilators and diuretics.
• Causes QT interval prolongation.
• Misc.
• Diminishes effects of anticoagulants. Possible hyperthermia in the
presence of hypothalamic dysfunction.
• Neuroleptic malignant syndrome.

11. Metoclopramide
Uses
1. digestive disorders, e.g. hiatus hernia, reflux oesophagitis, and gastritis.
2. nausea and vomiting due to a variety of causes, e.g. drugs (general
anaesthetic agents, opiates, and cytotoxic gents), radiotherapy, hepatic and
biliary disorders.
3. diagnostic radiology of the gastrointestinal tract.
4. migraine, and 5. post-operative gastric hypotonia.
Main actions
Increased gastrointestinal motility and antiemetic.

12. Presentation
• As 10 mg tablets,
• A syrup containing 1 mg/ml, and as a clear,
• Colorless solution for injection containing 5 mg/ml of metoclopramide
hydrochloride.
Mode of action
• The antiemetic effects of the drug appear to be mediated by:
1. Central dopaminergic (d2) blockade, leading to an increased threshold
for vomiting at the chemoreceptor trigger zone and
2. Decrease in the sensitivity of visceral nerves supplying afferent
information to the vomiting center.

13. Mode of action
The effects of metoclopramide on gastrointestinal motility appear to be
mediated by:
1. Antagonism of peripheral dopaminergic (D2) receptors
2. Augmentation of peripheral cholinergic responses, and 3. Direct action
on smooth muscle to increase tone.
Routes of administration/doses
• Metoclopramide may be administered orally, intravenously, or
intramuscularly;
• The adult dose by all routes is 10 mg 8-hourly.
• A dose of 1–2 mg/kg is recommended for the treatment of nausea and
vomiting associated with cisplatin treatment.

14. Effects
• CVS
• There have been occasional reports of hypotension during general
anaesthesia and cardiac arrest,
• Dysrhythmias, and hypertension in patients with phaeochromocytoma
following the administration of metoclopramide.
• Cns
• Metoclopramide raises the threshold for vomiting at the chemoreceptor
trigger zone and prevents apomorphine-induced vomiting in man.
• The drug has neuroleptic effects (including an antipsychotic action),
• As would be expected of a centrally acting dopamine antagonist
• GU the drug may increase ureteric peristaltic activit

15. Cyclizine
Uses
• Cyclizine is used in the treatment of nausea and vomiting due to:
1. opioid or general anaesthetic agents
2. motion sickness
3. radiation sickness, and
4. Ménière’s disease
Main action Antiemetic.

16. Presentation
• As tablets containing 50 mg of cyclizine hydrochloride and as a clear,
• colourless solution for injection containing 50 mg/ml of cyclizine lactate
which should be protected from light.
• Fixed-dose combinations with morphine, caffeine, ergotamine, and
dipipanone are available. It has a pH of 3.2.
Mode of action
• Cyclizine is a competitive antagonist of histamine at H1 receptors and has
anticholinergic activity at the muscarinic M1, M2, and M3 receptors.
• The antiemetic effect is mediated via blockade of central histamine and
muscarinic receptors within the vomiting area of the chemoreceptor
trigger zone.
• Cyclizine produces its antiemetic effect within 2 hours and lasts
approximately 4 hours.

17. Route of administration/doses
• Cyclizine may be given orally or by intramuscular or intravenous injection.
• Given the low pH of the parenteral preparation, injection by either route
may be painful.
• The maximum daily dose is 150 mg.The paediatric dose is 1 mg/kg.
Effects
• CVS The drug has mild anticholinergic action and can produce tachycardia
and hypotension due to alpha-blockade.
• RS Cyclizine, although it has antihistaminergic properties, does not
completely reverse anaphylactic bronchospasm,
• CNS The principal effect of the drug is antiemetic, with a slight degree of
sedation.

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