Irinotecan Sun (Irinotecan Hydrochloride Trihydrate)

• Irinotecan is a topoisomerase I inhibitor used primarily in colorectal cancer chemotherapy.
• Metastatic colorectal cancer: used in combination regimens to improve overall survival and disease control.
• Colorectal cancer (first‑line): combined with fluorouracil and leucovorin to achieve tumor response.
• Colorectal cancer (second‑line): administered after failure of first‑line therapy to provide additional disease control.

• Irinotecan is converted intracellularly to its active metabolite SN‑38, which binds to the DNA‑topoisomerase I complex and stabilizes it. This prevents the re‑ligation of single‑strand DNA breaks during replication, leading to accumulation of DNA damage, inhibition of tumor cell proliferation, and ultimately cell death.

Irinotecan is associated with a range of adverse reactions that vary in frequency and severity.

Common Side Effects

• Neutropenia: reduced white blood cell count increasing infection risk.
• Diarrhea: often severe and may require supportive care.
• Nausea and vomiting: typical chemotherapy‑related symptoms.
• Alopecia: hair loss during treatment.
• Fatigue: generalized tiredness affecting daily activities.
• Anorexia: loss of appetite.

Serious or Rare Side Effects

• Febrile neutropenia: fever with low neutrophils requiring urgent medical attention.
• Severe colitis or intestinal perforation from intense diarrhea.
• Hepatic toxicity: elevated liver enzymes or jaundice.
• Hypersensitivity reactions: rash, bronchospasm, or anaphylaxis.
• Pulmonary toxicity: interstitial pneumonitis or fibrosis.

• Prior to initiating therapy, several safety measures should be observed.
• Blood count monitoring: perform complete blood counts before each cycle to detect neutropenia.
• Liver function assessment: evaluate hepatic enzymes prior to treatment and during therapy.
• Bowel obstruction risk: assess for pre‑existing gastrointestinal obstruction before infusion.
• Dose adjustment: modify dose in patients with hepatic impairment.
• Allergy screening: avoid use in individuals with known hypersensitivity to irinotecan or formulation components.
• Store at controlled room temperature: keep in original container, protect from light and moisture.

Irinotecan may interact with other medicines, affecting efficacy or safety.

Major Interactions (Avoid)

• Strong CYP3A4 inducers (e.g., rifampin): may markedly reduce irinotecan exposure.
• Concurrent myelosuppressive chemotherapy: increases risk of severe neutropenia and thrombocytopenia.
• Cholinesterase inhibitors (e.g., neostigmine): can exacerbate irinotecan‑induced diarrhea.

Moderate Interactions (Monitor Closely)

• Warfarin: may alter INR, requiring closer coagulation monitoring.
• Fluconazole and other CYP3A4 inhibitors: can increase irinotecan plasma levels, necessitating dose adjustment.
• Antidiarrheal agents (e.g., loperamide): may mask early signs of severe diarrhea.