Drugs act by specifically interfering with biochemical processes
within the body. At first, drugs have to reach their target,
i.e. the site where the therapeutic action is required (also
called target site). Whatever the application of a drug (oral,
intravenous, topical etc.), its journey to the target site is
not at all an easy task. The circulatory blood stream and
proteins like the human serum albumin and the high density (HDL)
and low density (LDL) lipoproteins, usually transport drugs
throughout the body. Sometimes, artificial carriers, which are
specially designed by chemist and pharmacologists and make part
of the drug formulation, facilitate drug delivery. When a drug
reaches its target site, it enters in action, which means that
it starts interacting with specific biological substrates such
as the proteins, the DNA etc. In the case of DNA, this
interaction could result for example, in interrupting the
replication process, which eventually leads to cell death
(objective of cancer therapy). Nevertheles