Friday, March 14, 2008

Pharmacogenomics: A Tailored Approach to Therapy

Pharmacogenomics is a new scientific discipline made possible by the genome project. The mapping of the human genome has opened up enormous possibility for the identification and treatment of disease. Pharmacogenomic research focuses on the relationship between genes and drugs. One such example is a look at drug side effects and adverse reactions. We are beginning to identify why some individuals experience side effects to some drugs while others respond favorably with no adverse reaction to the very same drug. Some side effects can be life threatening, in fact, adverse drug reactions are a major cause of hospitalizations.

Stevens-Johnson syndrome (toxic epidermal necrolysis) is a severe and potentially life threatening reaction. It is now known that individuals of Asian descent have a gene referred to as HLA-B 1502. HLA's are human leukocyte antigens, proteins on white blood cells, that are responsible for recognizing foreign invaders. Some HLA subtypes see a particular drug as harmful and start an immune reaction. In the case of HLA-B 1502 it perceives carbamazepine (a popular seizure medication) as a foreign invader. Five percent of individuals that test positive for this gene will develop Stevens-Johnson Syndrome. It is recommended that individuals of Asian descent be offered other alternatives until genetic testing is made available to all and becomes more affordable.

The following drugs have a higher rate of causing hypersensitivity reactions: allopurinol, sulfonamides, hydralazine and others. Their HLA substypes are also being identified. In addition, HIV guidelines also urge screening for HLA-B5701 before starting abacavir to avoid a hypersensitivity reaction.

This is an exciting area of research, one which promises a tailored approach to therapy, in this case drug therapy.

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