Injosetron (Palonosetron)

Injosetron, a selective 5‑HT3 receptor antagonist, is used to manage nausea and vomiting associated with specific medical procedures and treatments.

• Chemotherapy‑induced nausea and vomiting: prevents and controls acute and delayed emesis in patients receiving cytotoxic chemotherapy.
• Postoperative nausea and vomiting: reduces the incidence and severity of nausea and vomiting after surgical procedures.
• High‑risk emesis patients: provides prolonged antiemetic protection for individuals identified as high risk for severe nausea and vomiting.

• Palonosetron binds with high affinity to the serotonin 5‑HT3 receptor located on vagal afferent nerves in the gastrointestinal tract and the central vomiting centre. By competitively antagonizing this ligand‑gated ion channel, it blocks serotonin‑mediated signalling that triggers the emetic reflex. Its prolonged receptor occupancy and allosteric effects contribute to an extended duration of antiemetic activity compared with first‑generation 5‑HT3 antagonists.

Palonosetron may cause adverse reactions, most of which are mild and transient.

Common Side Effects

• Headache: mild to moderate intensity.
• Constipation: reduced bowel movements.
• Fatigue: feeling of tiredness.
• Dizziness: light‑headed sensation.
• Injection site erythema: redness at the infusion site.
• Diarrhoea: loose stools.

Serious or Rare Side Effects

• QT interval prolongation: potential cardiac rhythm disturbance.
• Severe hypersensitivity reactions: including anaphylaxis.
• Serotonin syndrome: rare but may occur with other serotonergic agents.

When using Injosetron, clinicians should consider several precautionary measures to ensure safe administration.

• Hepatic impairment: use with caution and monitor liver function.
• Cardiac risk: assess baseline ECG and monitor QT interval, especially in patients with known arrhythmias.
• Concomitant serotonergic drugs: evaluate risk of serotonin syndrome.
• Pregnancy and lactation: avoid unless benefit outweighs potential risk, as safety data are limited.
• Drug interactions: review all concomitant medications for potential interactions.
• Store at 2‑8 °C: keep refrigerated, protect from light, do not freeze.

Palonosetron can interact with other medicines, affecting its efficacy or safety.

Major Interactions (Avoid)

• Co‑administration with other QT‑prolonging agents: may increase risk of cardiac arrhythmia.
• Strong CYP3A4 inhibitors (e.g., ketoconazole): can raise palonosetron plasma levels.

Moderate Interactions (Monitor Closely)

• Other 5‑HT3 antagonists: additive antiemetic effect may increase side‑effect risk.
• Serotonergic agents (e.g., SSRIs, tramadol): monitor for signs of serotonin syndrome.
• CYP3A4 inducers (e.g., rifampin): may reduce palonosetron exposure and effectiveness.