Pharmacogenetics refers to the:

• A. Inherited difference in the way a medication is metabolized and/or the effect of a medication in an individual
• B. Study of the absorption, distribution, metabolism, and excretion of drugs in the body
• C. The way in which a medication is developed
• D. Absorption rate of medication in relation to the amount of food that is ingested

Answer: (A)

Pharmacogenetics focuses on inherited genetic differences that change how a person metabolizes a drug and how the drug’s effect may vary from person to person. These genetic variations can alter enzyme activity, drug transport, or drug targets, leading to faster or slower drug clearance and to stronger or weaker therapeutic or adverse effects. A classic example is variation in drug-metabolizing enzymes like CYP450s, which can make someone a poor or ultra-rapid metabolizer for certain medications, affecting dosing and safety. This concept underpins personalized medicine, where genotype information helps tailor drug choice and dose to the individual.

This differs from general pharmacokinetics, which studies how the body handles a drug in terms of absorption, distribution, metabolism, and excretion without emphasis on genetic differences. It also differs from drug development and from factors like food that influence absorption, which are not about inherited genetic variation.