The same drug can help one person and harm another. Pharmacogenomics studies how genetic variation influences an individual’s response to medications. Variants in drug-metabolizing enzymes, transporters, and targets alter efficacy and risk of side effects.

Classic examples include CYP2C19 variants that affect clopidogrel activation and HLA alleles that predict severe reactions to certain drugs. Guidelines from professional organizations translate genotype results into dosing recommendations or alternative therapies.

Preemptive testing panels are being adopted by some health systems so that results are available when a drug is prescribed. Implementation requires decision-support tools and clinician education. As evidence accumulates, pharmacogenomics is becoming a practical component of safer, more effective prescribing.

• Study of genetic effects on drug response
• Involves metabolizing enzymes and drug targets
• Guides dosing and drug selection
• Supported by clinical guidelines