Cytostatic agents are pharmaceutical agents that inhibit cell division and cell growth. They are particularly damaging to fast-growing cells with high metabolic rates. That's why they are used for cancer therapy. Of course, because the drugs can not know which cells they need to "act on" because they have a harmful effect on the body, they can also affect healthy cells. This leads to the typical side effects that are known in cancer therapy.
The side effects of all cytotoxic drugs are similar: they lead eg to gastrointestinal complaints, loss of appetite, vomiting, diarrhea, hair loss, liver damage, increased risk of infection, lowering the number of corpuscles. There are various chemical and pharmacological groups of cytotoxic agents, such as antibiotics, mitotic inhibitors (block cell division), antimetabolites (inhibit vital metabolic processes) and certain antibiotics; in a broader sense also hormones, eg estrogens in prostate cancer and androgens in mammary cancer.