Serum Drug Level - The Marker for Drug Toxicity & Pharmacogenetics for Personalized Prescriptions: An Overview of the Past, Present and Future

In the present fast growing scientific technological scenario it is but natural to demand the right medicine at the right dose and therapeutic efficacy, with least side effects by one and all. Bioavailibility studies of the drug being used in therapy could give the physician a clearer picture of the concentration at which the individual will show a therapeutic /toxic effect. No doubt the various pharmaceutical-manufacturing methods introduced recently provides enough scope to reduce the drug concentration in each prescribed drug while increasing the bioavailibility.

Variations in pharmacokinetic properties such as acetylation, oxidation, and hydrolysis, and geneticmetabolic disorders such as glutathione synthase deficiency, glucose 6 phosphate dehydrogenase deficiency etc ., necessitate that therapy be viewed in an individualized manner. This is where pharmacogenetics can help.

Adverse drug reactions are the 4th most common cause of death in the world. One patient is different from another in expressing the ADR in a dose related manner. The rate of ADR is increasing with polyprescriptions, which is due to bioavailibility variations occurring by interaction between the drugs. A first line drug for one need not be necessarily applicable to another due to genetic variation. Bioavailibility in the true sense is to be viewed more critically. No doubt the bioavailibility data gives us an overview of the drug's pharmacokinetic behaviour. It is now clear that much individuality in drug response is inherited: this genetically determined variability in drug response defines the research area known as pharmacogenetics.

Development of new drugs for individuals with specific genotypes is “drug statification” which might take up a grand lobby in the future. All the major drug metabolizing P450 enzymes have been identified and cloned, and the major gene variants that cause inter-individual variability in drug response are related to adverse drug reactions. This information now provides the basis for the use of predictive pharmacogenetics to yield drug therapies that are more efficient and safer. Pharmacogenetics testing as it advances will substantially reduce the need for hospitalization due to Adverse Drug Events/Toxicity, and its associated costs.