Cancer can be a long and painful disease. Many times, the drugs that are used to fight cancer can be just as excruciating as the disease itself.
Antibiotics, as the name implies, work against life, or more specifically, against living cells. Most antibiotics, such as penicillin or erythromycin, attack bacterial cells in specific ways that don't affect animal cells. That way the bacteria causing the infection are destroyed without harming the patient.
But cancer is different from other diseases in that the cells in a cancer tumor are human cells. The main difference between cancer cells and healthy cells is that the cancer cells are multiplying uncontrollably. Therefore, the antibiotics that attack cancer cells might also attack healthy cells.
One way chemotherapy drugs work is by interrupting the production of DNA. All cells have DNA, which must be reproduced when new cells are made. Since DNA is involved in reproduction, the cells that are reproducing the fastest, such as cancer cells, are also the ones that are producing the most DNA. For this reason, the rapidly growing cancer cells are most affected by drugs that interrupt the production of DNA.
The cells in the hair follicles and in the stomach lining also reproduce faster than most other cells. Consequently, when chemotherapy interrupts DNA production in cancer cells, it also interrupts DNA production in hair follicles and in the stomach lining, causing chemotherapy patients to lose hair and experience severe stomach problems.
The side effects of chemotherapy are worse than the side effects of most other drugs because chemotherapy attacks human cells, while other antibiotics attack specifically bacteria cells.