Ondansetron: Effects, Uses & Risks

Ondansetron is a major antiemetic that belongs to the setrone class of drugs. Ondansetron achieves its effects by causing inhibition of 5HT3 receptors. Because of this mode of action, ondansetron is also considered a serotonin receptor antagonist. The drug is marketed under the trade name Zofran and is used to treat nausea, vomiting, and emesis.

What is ondansetron?

Ondansetron is an active ingredient used in human medicine to treat nausea, severe nausea, and vomiting. It is therefore considered an antiemetic. Its effectiveness is based on its activity in the brain. There, ondansetron causes an inhibition of the so-called 5HT3 receptors, which has a direct influence on the concentration of the neurotransmitter serotonin in the brain. This is a mode of action that is also used with certain psychotropic drugs. In chemistry, ondansetron is also known as (RS)-9-methyl-3-(2-methylimidazol-1-ylmethyl)-1,2,3,9-tetrahydrocarbazol-4-one, which corresponds to a chemical molecular formula of C 18 – H 19 – N 3 – O. The morale mass of the drug is approximately 293.37 g/mol. Ondansetron is subject to prescription and pharmacy prescriptions. The drug is usually taken orally in the form of film-coated tablets. In acute cases, an intravenous dosage form may also be indicated.

Pharmacologic effects on the body and organs

After taking ondansetron, patients experience a noticeable reduction in nausea. This inhibitory effect is due to inhibition of the neurotransmitter serotonin. In addition to the feeling of hunger, serotonin also controls the activity of the gastrointestinal tract and is also an important factor in influencing the human mood. If the neurotransmitter is present in too high a concentration in the human body, activation of the visceral afferent vagus and the vomiting center of the central nervous system (also CNS) occurs. Ondansetron docks to the 5HT3 receptors of the brain, to which serotonin usually also binds. Since the corresponding receptors are no longer available for the neurotransmitter, an inhibition occurs. This reduces the existing nausea. Since various cytostatic drugs and various radiation therapies lead to a massive increase in serotonin levels, which can cause nausea, ondansetron is administered primarily to cancer patients. However, ondansetron is less suitable for the treatment of nausea not triggered by serotonin, which is why motion sickness must be treated with other preparations. Unlike other antiemetics, ondansetron does not exert effects at the histamine, muscarinic, or dopamine receptors, which is why the drug is not considered a psychotropic drug and has no appreciable application in the treatment of mental illness.

Medical application and use for treatment and prevention.

Ondansetron is usually administered as film-coated tablets for oral administration. In acute cases, administration of an infusion solution or administration by syringe may also be used. The main area of application for ondansetron is cancer therapy. Here it is used to combat the side effects of chemotherapy or radiotherapy. Both cause a pathogenic increase in serotonin levels, which can lead to severe nausea. Ondansetron counteracts this. Because of its specific mode of action, which relies on inhibition of serotonin, it is not indicated for motion sickness therapy.

Risks and side effects

Ondansetron may cause adverse side effects. It should not be taken at all if there is a medical contraindication. This is always the case if there are specific circumstances that call the success of treatment into question from a medical point of view (contraindication). For example, ondansetron must not be taken if there is a known intolerance or hypersensitivity (allergy). Patients suffering from cardiac arrhythmias in the form of long-QT syndrome must also not take ondansetron. Furthermore, there is a contraindication in case of cardiac muscle weakness as well as during breastfeeding and pregnancy. In addition, attention must be paid to potential interactions with other active ingredients. For example, ondansetron must not be taken at the same time as apomorphine, a drug used to treat Parkinson’s disease. The two active ingredients lead to reciprocal changes in efficacy, which can result in unmanageable risks.Massive drops in blood pressure often occur, which can lead to fainting. In addition, ondansetron is known to interact with the drugs phenytoin, carbamazepine and rifampicin. Again, concomitant use should be avoided. Furthermore, ondansetron leads to decreased efficacy of the analgesic tramadol, so other analgesic preparations may have to be used.