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Irinotecan, in contrast to topotecan, its cousin, which is a, again, campothecin from the Chinese tree, irinotecan is notorious for diarrhea. This is something that we have to aggressively stay on top of because the diarrhea doesn’t just make you pretty dehydrated. It can also cause you to get low on your electrolytes, potassium, and magnesium and other things which can cause irregular heart rates, muscle cramping, and muscle pains. So that diarrhea and control of it is very important. Irinotecan is dependent on the liver function. So that’s what we need to look at to make sure that you can get the dose you need. Whereas topotecan depends on the kidney function. Irinotecan comes with what we call acute diarrhea, which happens within 24 hours of your treatment. This is because irinotecan is what we call cholinergic.
And that’s basically a term for certain catacholamines and proteins that we use in the body. It speeds them up to cause the diarrhea. And one way to treat it is what’s called atropine, which is an anti-cholinergic. So we’ll give that to accommodate for what that diarrhea could be in the 24 hours after delivery of the drug. Irinotecan then causes what’s called late diarrhea, which happens after your treatments, usually after two to three doses. You can notice, “Man, my diarrhea is a lot worse.” In these circumstances, we use what’s called Loperimide, as well as an antibiotic, specifically fluoroquinolone, but we can only incorporate those if you let your physician know that, “Hey, my frequency of diarrhea has gone up considerably after these two or three doses.” So that’s something you want to watch for very closely as well. Irinotecan does have a cousin called lyposomal irinotecan. This is most commonly just used in pancreatic cancer, but the symptoms can be a little less severe with the liposomal irinotecan than the irinotecan by itself.
