Indications
Topotecan for injection is used on its own for metastatic carcinoma of the ovary. It is given when the disease has progressed on or after initial or later chemotherapy. It is also used as a single agent for small cell lung cancer in patients with platinum-sensitive disease. These are patients whose disease progressed at least 60 days after first-line chemotherapy was started. For cervical cancer, topotecan for injection is given together with cisplatin. This applies to patients with Stage IV-B, recurrent or persistent carcinoma of the cervix that can't be treated with curative treatment.
⚠️ Always consult a registered physician before taking any medicine.
Pharmacology
Topotecan works in the same way as irinotecan. It is believed to damage cells mainly during the S-phase of DNA synthesis. Topoisomerase I eases the torsional strain in DNA by making reversible single strand breaks. Topotecan binds to the topoisomerase I-DNA complex and stops these single strand breaks from being religated.
The resulting ternary complex gets in the way of the moving replication fork. This leads to replication arrest and to lethal double-stranded breaks in DNA. Mammalian cells can't repair these double strand breaks efficiently, so the formation of the ternary complex eventually leads to apoptosis (programmed cell death).
Topotecan mimics a DNA base pair and binds at the site of DNA cleavage, where it intercalates between the upstream (-1) and downstream (+1) base pairs. This intercalation displaces the downstream DNA, so the cleaved strand can't be religated. Because Topotecan binds specifically to the enzyme-substrate complex, it acts as an uncompetitive inhibitor.
Pregnancy & Breastfeeding
Topotecan is in pregnancy category D. This means there is positive evidence of risk to the human foetus. Even so, a pregnant woman may still receive it if the benefit is acceptable despite that risk, for example when the medicine is needed in a life-threatening situation, or for a serious disease where safer drugs cannot be used or don't work.
⚠️ Talk to your doctor before taking any medicine during pregnancy or while breastfeeding.
Dosage Reference
⚠️ Reference ranges from official sources only. Consult your doctor for personalized dosing.