Drugs are chemicals of low molecular masses (~100 – 500u).
These interact with macromolecular targets and produce a biological response.
When the biological response is therapeutic and useful, these chemicals are called medicines and are used in diagnosis, prevention and treatment ofdiseases.
If taken in doses higher than those recommended, most of the drugs used as medicines are potential poisons.
Use of chemicals for therapeutic effect is called chemotherapy
Treatment of cancer:
The common approaches for treatment of cancer are surgery, radiation therapy and immunotherapy.
In radiotherapy, tumor cells are irradiated lethally, taking proper care of the normal tissues surrounding the tumor mass.
Several chemotherapeutic drugs are used to kill cancerous cells.
Some of these are specific for particular tumors. Majority of drugs have side effects like hair loss, anemia, etc.
Most cancers are treated by combination of surgery, radiotherapy and chemotherapy.
Tumor cells have been shown to avoid detection and destruction by immune system.
Therefore, the patients are given substances called biological response modifiers such as α-interferon which activates their immune system andhelps in destroying the tumor.