Topoisomerase Inhibitors

Topotecan (Hycamtin) or irinotecan (Camptosar) are topoisomerase inhibitors that cause DNA damage to cancer cells.

• Who should not use these medications: Persons with the following conditions should not use topoisomerase inhibitors:  
  
  
  • Allergy to topoisomerase inhibitors
  
  
  
  • Extremely low white blood cell or platelet counts  


• Use: Topoisomerase inhibitors are administered by an IV injection during the first 5 days of each chemotherapy cycle.



• Drug or food interactions: The risk of topoisomerase inhibitors further reducing blood cell counts and causing anemia or bleeding may increase when they are used with other chemotherapy drugs. The herbal antidepressant drug St. John’s wort may decrease effectiveness of irinotecan. Phenytoin (Dilantin) or carbamazepine (Tegretol) may also decrease the effectiveness of topoisomerase inhibitors.



• Side effects: Topoisomerase inhibitors may cause a person to bleed or to develop infections more easily. A doctor will check blood and urine for abnormalities that may be caused by these drugs.
  
  
  • A doctor should be contacted immediately if any of the following side effects occur:  
    
    
    • Allergic reaction symptoms, including fast heartbeat, itching or hives, swelling in the face or hands, swelling or tingling in the mouth or throat, chest tightness, and wheezing
    
    
    
    • Unexplained fever, chills, or sore throat
    
    
    
    • Severe nausea, vomiting, or diarrhea
    
    
    
    • Sores or ulcers around or in the mouth
    
    
    
    • Extreme weakness or tiredness
    
    
    
    • Redness, pain, or swelling where the IV is given
    
    
    
  • Other side effects include the following
    
    
    • Constipation
    
    
    
    • Poor appetite
    
    
    
    • Rash
    
    
    
    • Stomach pain
    
    
    
  • Once the diarrhea starts, an antidiarrheal medication should be taken and the doctor should be informed.