Conventional cytotoxic medicine

The medicines belonging to the cytotoxic chemotherapy group are also known as anti-neoplastic agents and are used to block mitosis, i.e. cell division. They are usually used in anti-cancer therapy. They are a group of dozens of medicines including the alkylating agents (platinum salts, nitrogen mustards, etc.), the antimetabolites, the intercalating agents, and the antimitotics.

How do the antineoplastics work?

Cytotoxic chemotherapy medicines inhibit proliferation of tumour cells. Their action mechanisms vary depending on the type of medicine: - alkylating agents bind to cellular DNA and cause breaks, preventing cancer cells from replicating (multiplying). Antimetabolites act on the synthesis of DNA and RNA. To some extent they prevent the body using chemical substances known as metabolites which are essential for the production of new cells. Intercalating agents act on the structure of the DNA itself. The molecules in question "intercalate" between the DNA strands; - the anti-mitotic agents (or spindle poisons) act during cell division when the chromosomes split for replication.

Do they have any contraindications or precautions?

Their side effects also vary depending on the class of medicine. They have a lot of potential side effects. Because of the way they act, cytotoxics are not selective. In other words, they do not target tumour cells exclusively. The anti-cancer agents can therefore also attack healthy cells. The most commonly reported side effects are nausea, vomiting, persistent fatigue, hair loss, neutropenia (a fall in the number of white blood cells). Mucosal ulcers (particularly in the gastro-intestinal tract) and mucitis (aphthous ulcers) are also observed sometimes. Some treatments can also cause cystitis and even renal toxicity.

Sources:

• 47^th Congress of theAmerican Society of Clinical Oncology (ASCO), Chicago, 3-7 June 2011
• Merck Manual, 4^th edition