**4. Utility of pharmacogenomics and clinically available tests**

One of the earliest uses of sequencing the human genome was expected to be clinical testing to predict medication response. New pharmacogenetic tests have a positive or substantial impact on prescription practice, such as the adoption of a different medication or dosage regimen, which results in quantifiable improvements in patient

#### *Interplay between Pharmacokinetics and Pharmacogenomics DOI: http://dx.doi.org/10.5772/intechopen.108407*

outcomes [56]. Despite the availability of tests, several barriers have hindered their implementation in ordinary clinical practice, including poor knowledge among healthcare professionals, ethical concerns, and the cost-effectiveness of the clinical outcome [57]. Furthermore, determining medication responses in complex multifactorial characteristics is difficult due to the interaction of many genes and genetic variations with environmental variables, and the genetic element may only have a minor influence on the outcome of treatment [58]. Much of the early published research focused on single pathogenic mutations that are particularly conspicuous or that have an obvious or unambiguous "all or nothing" therapy [59]. In fact, the likelihood of medication benefit and risk is frequently a continuum with a broad range of variance among individuals in a community, and relying on a single predictive biomarker to guide the treatment of serious diseases may not be accurate or reliable enough. Confirming analytic validity (test accuracy and reliability) and determining clinical utility should be the first steps in assessing pharmacogenetic indicators in clinical treatment [60]. There are additional health-economic issues to address, such as whether the genetic markers are common enough in their patient population to warrant the screening expenses [61]. The practicality of applying the biomarker testing method in a way that does not delay patient care will then be examined by policymakers and funding agencies. When compared with the current availability of preemptive testing for many genetic markers, the previous practice of single gene as needed, or "one at a time'" testing, might appear inefficient and costly [60]. Several obstacles to pharmacogenomics implementation have been identified and reported in the literature. Many of these issues are comparable with those that arise when introducing any new therapeutic service in a variety of practice settings. Securing administrative and provider buy-in, building effective physician relationships, and integrating a new service into an established clinical workflow are just a few of the common obstacles [62]. Still, fast testing utilizing multi-gene panels is becoming more widely available; an individual's genetic data from a single sample may now be used to advise them about a variety of treatment options that may occur later in their lives.
