Last reviewed 2026-04-20 · How we verify

Camptosar (Irinotecan Hydrochloride)

Camptosar works by blocking the enzyme topoisomerase I, which is necessary for DNA replication, thereby preventing cancer cells from dividing and growing.

Camptosar (Irinotecan Hydrochloride) is a topoisomerase inhibitor, a small molecule drug that targets and inhibits the enzyme topoisomerase I, which is involved in DNA replication. It was originally developed by Pfizer Inc and is currently owned by the same company. Camptosar is used to treat various types of cancer, including adenocarcinoma of the pancreas, metastasis from malignant tumors of the colon, and secondary malignant neoplasms of the pancreas. The drug is off-patent, with 23 generic manufacturers available, and has a half-life of 9.0 hours with a bioavailability of 8%. Key safety considerations include its potential to cause severe diarrhea and neutropenia.

At a glance

Mechanism of action

Irinotecan is derivative of camptothecin. Camptothecins interact specifically with the enzyme topoisomerase I, which relieves torsional strain in DNA by inducing reversible single-strand breaks. Irinotecan and its active metabolite SN-38 bind to the topoisomerase I-DNA complex and prevent religation of these single-strand breaks. Current research suggests that the cytotoxicity of irinotecan is due to double-strand DNA damage produced during DNA synthesis when replication enzymes interact with the ternary complex formed by topoisomerase I, DNA, and either irinotecan or SN-38. Mammalian cells cannot efficiently repair these double-strand breaks.

Approved indications

• Adenocarcinoma of pancreas
• Metastasis from malignant tumor of colon
• Secondary malignant neoplasm of pancreas

Boxed warnings

• WARNING FULL PRESCRIBING INFORMATION WARNING: DIARRHEA and MYELOSUPPRESSION Early and late forms of diarrhea can occur. Early diarrhea may be accompanied by cholinergic symptoms which may be prevented or ameliorated by atropine. Late diarrhea can be life threatening and should be treated promptly with loperamide. Monitor patients with diarrhea and give fluid and electrolytes as needed. Institute antibiotic therapy if patients develop ileus, fever, or severe neutropenia. Interrupt Irinotecan hydrochloride injection and reduce subsequent doses if severe diarrhea occurs. Severe myelosuppression may occur. WARNING: DIARRHEA and MYELOSUPPRESSION See full prescribing information for complete boxed warning . • Early and late forms of diarrhea can occur. Early diarrhea may be accompanied by cholinergic symptoms which may be prevented or ameliorated by atropine. Late diarrhea can be life threatening and should be treated promptly with loperamide. Monitor patients with diarrhea and give fluid and electrolytes as needed. Institute antibiotic therapy if patients develop ileus, fever, or severe neutropenia. Interrupt irinotecan hydrochloride injection and reduce subsequent doses if severe diarrhea occurs. • Severe myelosuppression may occur.

Common side effects

• Diarrhea
• Vomiting
• Nausea
• Fatigue/asthenia
• Stomatitis
• Pyrexia
• Decreased appetite
• Neutropenia
• Lymphopenia
• Thrombocytopenia
• Sepsis
• Gastroenteritis

Drug interactions

• phenytoin
• ritonavir

Key clinical trials

• Erlotinib Hydrochloride and Irinotecan Hydrochloride in Treating Patients With Advanced Solid Tumors (PHASE1)
• A Study to Compare Sacituzumab Tirumotecan (MK-2870) Monotherapy Versus Treatment of Physician's Choice as Second-line Treatment for Participants With Recurrent or Metastatic Cervical Cancer (MK-2870-020/TroFuse-020/Gog-3101/ENGOT-cx20) (PHASE3)
• Dinutuximab With Chemotherapy, Surgery and Stem Cell Transplantation for the Treatment of Children With Newly Diagnosed High Risk Neuroblastoma (PHASE3)
• M6620 and Irinotecan Hydrochloride in Treating Patients With Solid Tumors That Are Metastatic or Cannot Be Removed by Surgery (PHASE1)
• Neoadjuvant mFolfirinox With or Without Preoperative Concomitant Chemoradiotherapy in Patients With Borderline Resectable Pancreatic Carcinoma (PANDAS-PRODIGE 44) (PHASE2)
• Combination Chemotherapy With or Without Temsirolimus in Treating Patients With Intermediate Risk Rhabdomyosarcoma (PHASE3)
• Risk-Based Therapy in Treating Younger Patients With Newly Diagnosed Liver Cancer (PHASE3)
• Testing the Addition of an Individualized Vaccine to Durvalumab and Tremelimumab and Chemotherapy in Patients With Metastatic Triple Negative Breast Cancer (PHASE2)

Patents

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

• Camptosar CI brief — competitive landscape report
• Camptosar updates RSS · CI watch RSS
• Pfizer portfolio CI