The effects of drugs on the body (pharmacodynamics) and the effects of the body on a drug over time (pharmacokinetics) are considered in the science of pharmacology – pharmacokinetics are discussed in a separate article.
The availability of new medicines is often founded upon developments in the field of pharmacology following changes in our understanding of biochemical pathways.
New drugs are frequently developed in direct response to the emergence of new understanding of the disease process and the place of enzymes, hormones, neurotransmitters and immuno-active substances within it.
For example, new and novel medicines have followed the discovery of the role of serotonin in depressive illness, dopamine in schizophrenia and tissue necrosis factor in inflammatory diseases of the bowel and joints (Table 1).
The development and use of new drugs are also influenced by our understanding of the genetic basis of disease. With this understanding our ability to tailor therapy to based on individuals’ genetic make-up will increase.
The recent marketing of trastuzumab (Herceptin) is evidence of this. The drug is only effective in cases of breast cancer where the tumour over-expresses human epidermal growth factor 2 (HER 2). Before taking it patients must be genetically tested to ensure the drug is appropriate. Those who test positive for the presence of the protein are judged eligible for treatment.
The application of pharmacogenetic research by the pharmaceutical industry is likely to lead to more drugs that can be targeted at specific patients and diseases based on individual variations in genetic make-up. Research has already shown that patients with HIV experience varying degrees of hypersensitivity reactions to certain drugs directly as a consequence of genetic variations.
While an in-depth appreciation of clinical pharmacology is not essential to ensure safe drug use, it is important for practitioners to have a basic understanding of how a drug might be expected to exert its action once administered to a patient.
Such an understanding offers insight into how the effects of drugs might be experienced by the patient, and also the extent to which undesirable effects may be produced (Table 2).
Table 1. Drugs developed due to increased understanding of disease processes