Irinotecan Actavis (Irinotecan Hydrochloride Trihydrate)

• Irinotecan is a chemotherapy agent used in the treatment of colorectal cancer and related disease stages.
• Metastatic colorectal cancer: improves overall survival and disease control in patients with advanced disease.
• Adjuvant treatment of colon cancer: reduces the risk of recurrence after surgical resection.
• Advanced colorectal adenocarcinoma (combination therapy): forms part of multi‑drug regimens such as FOLFIRI to manage disease progression.

• After intravenous administration, irinotecan is converted by hepatic carboxylesterases to the active metabolite SN‑38. SN‑38 binds to the DNA‑topoisomerase I complex, stabilizing it and preventing relegation of single‑strand DNA breaks. This inhibition blocks DNA replication and transcription, ultimately leading to tumor cell apoptosis and death.

Irinotecan may cause a range of adverse reactions, from mild to severe. Monitoring and supportive care are essential during treatment.

Common Side Effects

• Diarrhea: may be early or delayed and can be severe.
• Neutropenia: reduced white blood cell count increasing infection risk.
• Nausea and vomiting: often managed with anti‑emetics.
• Fatigue: generalized tiredness during therapy.
• Abdominal pain: discomfort in the stomach area.
• Alopecia: hair loss in some patients.

Serious or Rare Side Effects

• Febrile neutropenia: fever with low neutrophil count requiring urgent care.
• Severe colitis: intense inflammation of the colon leading to dehydration.
• Allergic reactions: rash, itching, or anaphylaxis in rare cases.
• Hepatic toxicity: elevated liver enzymes indicating liver stress.
• Electrolyte imbalance: especially low potassium or magnesium levels.

Before initiating irinotecan therapy, clinicians should assess patient-specific risk factors and implement appropriate monitoring.

• Blood count monitoring: perform complete blood counts before each cycle to detect neutropenia.
• Liver function assessment: evaluate hepatic enzymes as irinotecan metabolism is liver‑dependent.
• Pregnancy risk: avoid use in pregnancy (Category D) and counsel women of childbearing potential.
• Dose adjustment: consider reduced dosing in patients with hepatic impairment.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Irinotecan interacts with several drug classes that can alter its efficacy or safety profile.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole): may increase SN‑38 exposure and toxicity.
• UGT1A1 inhibitors (e.g., atazanavir): can raise SN‑38 levels, heightening risk of neutropenia and diarrhea.
• Concurrent myelosuppressive agents: additive bone‑marrow suppression may be dangerous.

Moderate Interactions (Monitor Closely)

• CYP3A4 inducers (e.g., rifampin): may reduce irinotecan effectiveness.
• Anticoagulants such as warfarin: monitor INR as irinotecan can affect coagulation parameters.