Clinical application of pharmacogenomics

Area of Science:

• Pharmacogenomics
• Clinical Pharmacology
• Drug Metabolism

Background:

• Genetic variations, including cytochrome P450 (CYP) polymorphisms and human leukocyte antigen (HLA)-B*1502 allele, significantly impact drug disposition and patient response.
• Understanding these genetic factors is crucial for optimizing drug therapy and minimizing adverse events.

Purpose of the Study:

• To review the clinical utility of pharmacogenomics for specific drug classes: proton pump inhibitors (PPIs), codeine, and carbamazepine.
• To identify and discuss the limitations and challenges impeding the integration of pharmacogenomics into routine clinical practice.

Main Methods:

• Literature review of studies investigating pharmacogenomic applications for PPIs, codeine, and carbamazepine.
• Analysis of genetic polymorphisms (CYP2C19, CYP2D6) and their association with drug efficacy, toxicity, and adverse drug reactions.
• Examination of the role of HLA-B*1502 allele in carbamazepine-induced severe cutaneous adverse reactions.

Main Results:

• CYP2C19 genotype influences PPI pharmacokinetics, but evidence on its effect on Helicobacter pylori cure rates is conflicting.
• While CYP2D6 ultra-rapid metabolism is linked to neonatal adverse events with codeine, conclusive evidence on CYP2D6 polymorphisms' overall impact on codeine efficacy and toxicity is lacking.
• HLA-B*1502 allele presence necessitates pharmacogenomic testing before carbamazepine initiation in at-risk populations due to its association with Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN).

Conclusions:

• Despite available genotyping tests for CYP2C19 and CYP2D6, their clinical utility remains limited.
• Pharmacogenomic testing is essential for carbamazepine use in specific populations.
• Significant barriers to pharmacogenomic implementation include insufficient resources, inadequate provider knowledge, and ethical, legal, and social issues.