Bradycardia induced by irinotecan: a case report

Irinotecan chloride (CPT-11) is a new semi-synthetic camptothecin analogue which has encouraging antitumor activity against various malignancies. The major and unique toxicity of CPT-11 is diarrhea. Cardiovascular toxicity is rare and has not been found in clinical trials performed in Japan except for a very few cases of insignificant tachycardiac arrhythmia. We report a case of a 69-year-old man with recurrent colon cancer who suffered from bradycardia induced by infusion of CPT-11. Other toxicities including hematological toxicity and diarrhea were mild. Pharmacokinetic analysis using a limited sampling model revealed that the occurrence of bradycardia did not correlate with the excess of drug exposure. Although all of the cholinergic actions reported in the literature were mild, cardiotoxicity may come to be a clinically significant problem. If the events were examined more thoroughly, the cholinergic effect may be discovered more frequently. To administer CPT-11 safely needs meticulous monitoring not only for hematological toxicity and diarrhea but also for other cholinergic actions including bradycardia.