Have you ever had severe nausea and vomiting after surgery or during another major procedure? Or did you have unbearable morning sickness during pregnancy? It can be so uncomfortable that it can make our lives miserable. However, there is a very effective class of medication that doctors use to control this type of nausea and vomiting. That is what we are going to talk about today.
Simply put, what is this serotonin antagonist?
This is the name given to a class of medications. Simply put, these are medications that are given to prevent and treat nausea and vomiting. In medical terms, these are called `antiemetics`. Even if your doctor didn't mention this name directly, you may have been prescribed a medication in this class.
Several other names are used for this class of drugs:
- Serotonin-receptor antagonists
- 5HT3 receptor antagonists
- Serotonin blockers
While these names may sound a bit complicated, they all mean the same thing. That is, these medications block the action of a chemical in our body called serotonin . Let's look at it in a little more detail.
There are several types of medicines in this category that are commonly used in Sri Lanka and around the world:
- Ondansetron - This is the most well-known. It comes under the brand name Zofran®.
- Granisetron - available under the brand name Kytril®.
- Palonosetron - available under the brand name Aloxi®.
- Dolasetron - Although it was originally known as Anzemet®, it has now been withdrawn from use in countries like the United States.
This medicine is available in both pill and injection form.
What exactly is this medicine used for?
These medications are primarily approved to prevent nausea and vomiting in certain situations.
- Cancer treatments (Chemotherapy): These are essential to control the severe nausea that many people experience during chemotherapy.
- Radiation therapy: Radiation therapy for cancer can also cause nausea.
- After Anesthesia: Many people experience vomiting and nausea when they regain consciousness after undergoing anesthesia for surgery. This medication is given to prevent this.
These are prescribed by doctors as appropriate for both adults and children.
Sometimes doctors use these medications for other conditions. This is called "off-label" use. That is, they prescribe them because doctors know they are effective for a specific condition, even though they are not approved for that condition.
The following are examples of off-label uses of this medication:
- Treating (not just preventing) nausea and vomiting after surgery.
- To control severe nausea and vomiting (morning sickness) during pregnancy that is difficult to control with other treatments.
How does this medicine work inside our body?
To understand this, let's first simply understand what 'serotonin' is.
Serotonin is a neurotransmitter in our body. It's like a 'messenger'. This messenger controls many things, including our mood, sleep, and digestion. 90% of the serotonin in our body is found in the cells of our digestive system (intestines).
Imagine, when we receive something like chemotherapy, the cells in our intestines are damaged. Then, those cells suddenly release a large amount of serotonin into the bloodstream. This excess serotonin sends a message to the brain saying, "Something is wrong here!" That message is what makes us feel 'nausea' .
In order for these serotonin messages to reach the brain, they need to bind to specific 'receptors' in our gut and brain. These are like 'keyholes' that a key fits into. Serotonin is the key, and the receptor is the keyhole. When the key is inserted correctly, the door opens (i.e., the nausea message is sent).
`Serotonin Antagonist` medicine works by going to these keyholes (5-HT3 receptors) and blocking them. It's like putting a fake key in the keyhole. Then the real key (serotonin) can't get in. The message doesn't go to the brain. The result? The nausea and vomiting stop.
Side effects and risks of medications
This medication is generally very safe. However, like any medication, it has some side effects and a few things to be aware of.
Common side effects
- Headache
- Fatigue
- Constipation
These are usually not serious, but if they bother you, talk to your doctor.
Risks to be especially aware of
| Risk situation | What to know |
|---|---|
| Heart conditions | If you have heart rhythm problems such as Long QT syndrome , Ventricular arrhythmia , or other heart conditions, be sure to tell your doctor before taking this medication. Some people may experience changes in their heart rate due to this medication. |
| Serotonin Syndrome | This is the most dangerous and immediate condition. When taken with other medications that increase serotonin levels (e.g., SSRIs, SNRIs for depression), serotonin levels in the body can become dangerously high. It is very important to tell your doctor about all the medications you are taking. |
| Pregnancy | Although this medication does not carry a significant risk of birth defects, a small increase in the incidence of heart defects and cleft palate has been reported. Therefore, it should only be used during pregnancy on the advice of a doctor if the benefits outweigh the risks. |
A little more about Serotonin Syndrome
This is a serious condition that can even be life-threatening. Be very aware of the following symptoms. If you experience one or more of these, go to a hospital's Emergency Department (ETU) immediately.
- Restlessness, anxiety
- Nausea and vomiting
- Diarrhea
- Enlargement of the pupils of the eyes
- Body tremors
- Muscle twitching, stiffness
- Sweating, feeling cold
- Confusion, loss of consciousness
- Heart palpitations
- High blood pressure
- Elevated body temperature (over 101.3°F / 38.5°C)
- Seizures
- Loss of consciousness
When should I see the doctor again?
If you are taking this medication long-term, it is important to maintain regular contact with your doctor. Be sure to talk to your doctor in the following situations:
- If the side effects start to bother you.
- If your nausea and vomiting do not improve or get worse.
- If you are thinking of stopping the medication (never stop taking medication without asking your doctor).
Nausea is a very unpleasant experience. But the good news is that there are very effective medications available today to control such conditions. If you have this problem, talk to your doctor about it openly and get the treatment that is best for you.
Take-Home Message
- Serotonin Antagonist is a very effective medication that controls nausea and vomiting caused by cancer treatment, radiation therapy, and surgery.
- These work by blocking the action of a messenger called serotonin in the body.
- If you have a heart condition or are taking other medications (especially antidepressants), be sure to inform your doctor before taking this medication.
- Be aware of the symptoms of Serotonin Syndrome (anxiety, excessive sweating, muscle stiffness, rapid heartbeat) and go to a hospital's Emergency Department (ETU) immediately if you suspect such a condition.
- Always obtain and use these medications only under medical advice.
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