Ondansetron

It is a serotonin receptor antagonist.


Mechanism of action:
It has been shown to inhibit 5-HT3 receptors both centrally and peripherally and thus showing its anti-emetic activity.

It has been found that the chemotherapy causes degradative changes in the GI tract such as small intestine that causes the increased release of serotonin which then stimulates vagal and splanchnic nerves which leads to vomting center of the brain inducing vomiting.

The same stimulation has been found in the area postrema.

Ondansetron stops acute chemotherapy induced emesis by the inhibition of visceral afferent stimulation from the vomting center which may be:

1. Indirectly at the level of the area postrema

2. Directly inhibiting serotonin activity within the area postrema and chemoreceptor trigger zone.

Therapeutic uses:
It is used for Nausea and vomiting, which may be due to:

1. Cancer chemotherapy

2. Postoperative

3. Radiation induced.

Administration and dosage:
It can be administered orally or IV. The usual oral dose for cancer chemotherapy induced vomiting is 8 mg 30 minutes prior to chemotherapy induced vomiting.

Adverse effects:
It may cause headache, dizziness, restlessness and diarrhea (in some patients it may cause constipation). Fever and injection site reactions have also been reported.