Ondansetron: A Good Partner In The Fight Against Cancer

Ondansetron, with an indole structure, belongs to a class of drugs called serotonin 5-HT3 receptor antagonists. It is used to prevent nausea and vomiting caused by chemotherapy, radiation therapy, and various surgeries.

The Serotonin is a natural substance that may cause nausea and vomiting, so this drug works by blocking its action. As it is widely used in patients who are undergoing chemotherapy treatment for cancer, we will briefly comment on what this treatment is based on.

What is chemotherapy?

Well, chemotherapy is the use of drugs that aims to destroy cancer cells. It works by preventing cancer cells from growing and dividing into more cells, thus preventing the proliferation of malignant cells.

The problem is that since the drugs used for this type of treatment are very strong, in addition to damaging malignant cells, it also destroys healthy ones. This damage causes side effects that are related to chemotherapy, such as:

• Nausea and vomiting
• Diarrhea or constipation
• Alterations in the mucosa of the mouth
• Decrease in the number of blood cells
• Hair loss
• Skin and nail disorders
• Others

Ultimately, the goals of chemotherapy depend on the type of cancer and how much it has spread. Sometimes the main goal is to destroy all of the cancer and prevent it from coming back. If this is not possible, chemotherapy can slow or slow the growth of the cancer.

Next we will explain the following sections about ondansetron:

• Mechanism of action
• Pharmacokinetics
• Adverse reactions

Mechanism of action

Ondansetron, as mentioned before, is a selective 5HT-3 serotonin receptor antagonist. It blocks these receptors, both those found in the central zone in the chymoreceptor zone of the area postmas (the trigger zone of the chemoreceptor), as well as the peripheral ones in the centers of the upper GI tract.

It is a drug that, in addition to its selective antagonistic action on these receptors, also acts on gastrointestinal mobility.

It has no action on dopamine receptors, therefore it does not produce extrapyramidal effects, unlike metoclopramide or other antiemetics.

However, although it is not known whether the antiemetic effects of ondansetron are due to its central or peripheral action, it is known that the emetic responses of chemotherapy are related to serotonin secretion. Because ondansetron inhibits receptors for this hormone, it acts as an antiemetic.

Ondansetron Pharmakinetics

This drug is administered orally as it comes as a tablet. Once administered, it presents its maximum concentrations in plasma at one hour or two hours. It has an oral bioavailability of 60%.

Ondaserton undergoes extensive hepatic metabolism, but no clinically important metabolites are produced. That it is metabolized in this way is important when administering it together with other drugs, since it can undergo pharmacokinetic interactions with other substances at the liver level, which can produce toxic effects. Once metabolized, it is excreted in the feces or urine.

Another important fact to know is that it is bound to plasma proteins at a fairly high level, 76%. If we administer ondansetron with another drug that also binds to proteins, it can displace the antiemetic by increasing its free levels in the blood.

If the levels of the drug that is not protein bound are markedly increased, it can also produce undesirable effects in the patient.

In patients with kidney failure or in children, caution must be exercised when administering this drug since its half-life may vary.

Adverse reactions

Ondansetron is usually a drug that does not cause serious adverse effects and patients usually accept it without great problems. A great advantage it has over other antiemetics is the lack of extrapyramidal effects once administered.

However, like any medication, it is not exempt from adverse reactions, and therefore caution should always be exercised when taking any medication. The most common adverse effects of this drug that have been seen are, among others, the following:

• Headaches
• Constipation.
• Moderate sedation.

On the other hand, it can also trigger other symptoms not as common as the above. It can cause a moderate increase in transaminases, hypersensitivity reactions or dizziness.