What is Palonosetron?

Palonosetron is a class of antiemetics , which reduces nausea and vomiting. It is most effective drug in treatment of chemotherapy induced nausea and vomiting (CINV),post operative nausea and vomiting (PONV). Palonosetron is used in combination with other drugs like apripitants , glucocorticoid for maximum benefits.

How palonosetron works ?

Palonosetron act on 5HT3 receptor which are located in chemotactic trigger zone (CTZ) of brain. CTZ is located in medulla oblongata , a part of brain. Stimulation of this part of brain causes symptoms like nausea and vomiting. Palonosetron crosses blood brain barrier and blocks this receptors and stops feeling of nausea and vomiting. This class of drugs are also known as 5HT3 receptor antagonists.

📌 Uses

Palonosetron is commonly used to treat:

• Nausea
• Vomiting

Dosage

Adults : 2 mg per day (oral dose) usually given 1 hour before chemotherapy. Palonosetron is available as transdermal patch which is applied 24 to 48 hours before chemotherapy, and action lasts for 7 days.

⚠️ Side Effects

• Constipation
• Diarrhoea
• Lightheadedness
• QT prolongation ( ECG finding )

🔍 Precautions

Before taking palonosetron, tell your doctor if you have:

• 🤰 Pregnancy: It is advised to consult physician before taking palonosetron tablet.
• 🤱 Breastfeeding:: it is advised to consult your doctor regarding use of palonosetron while you are breastfeeding
• Liver:caution is advised. Dose adjustment is needed in case of liver disease.
• Kidney: standard dose of ondansetron is safe to use in kidney disease. If you have any pre-existing kidney disease,keep your doctor informed about this.

🔄 Drug Interactions

• Serotonergic Drugs (Risk of Serotonin Syndrome)

  Examples: Selective serotonin reuptake inhibitors (SSRIs, e.g., sertraline, fluoxetine), serotonin-norepinephrine reuptake inhibitors (SNRIs, e.g., venlafaxine), monoamine oxidase inhibitors (MAOIs), triptans (e.g., sumatriptan).

  Mechanism: Palonosetron blocks 5-HT3 receptors, but when combined with drugs that increase serotonin levels, it may contribute to serotonin syndrome, a potentially lifethreatening condition characterized by symptoms such as confusion, agitation, sweating, tremors, and high fever

• QT-Prolonging Drugs (Risk of Cardiac Arrhythmias)

  Examples: Antiarrhythmics (e.g., amiodarone, sotalol), antipsychotics (e.g., haloperidol,asenapine, ziprasidone), antibiotics (e.g., erythromycin, moxifloxacin), antifungals (e.g., fluconazole), and drugs like methadone, dronedarone

  Mechanism: Palonosetron can prolong the QT interval, increasing the risk of torsades de pointes, a life-threatening arrhythmia. Combining it with other QT-prolonging drugs heightens this risk, especially in patients with heart failure, electrolyte abnormalities (e.g., hypokalemia, hypomagnesemia), or congenital long QT syndrome.

• CYP3A4, CYP2D6, and CYP1A2 Inhibitors/Inducers

  Inhibitors: Ketoconazole, ritonavir, atazanavir (CYP3A4); fluoxetine, quinidine (CYP2D6); fluvoxamine (CYP1A2).

  Inducers: Phenytoin, carbamazepine, rifampin, apalutamide (CYP3A4).

  Mechanism: Palonosetron is metabolized by hepatic cytochrome P-450 enzymes (CYP3A4, CYP2D6, CYP1A2). Inhibitors may increase palonosetron plasma levels, potentially leading to enhanced side effects (e.g., headache, constipation, or QT prolongation), while inducers may decrease its efficacy by increasing excretion

📦 Storage

• Store at room temperature (68-77°F or 20-25°C)
• Keep in original container, tightly closed
• Protect from moisture and light

💡 Quick tips from experts:

• Palonosetron is advised by your doctor to treat symptoms like nausea and vomiting
• It starts action within 30 minutes after taking oral tablet.
• If you vomit within 1 hour of taking palonosetron tablet , take another tablet.