Drug-metabolizing enzymes pharmacogenetic differences

The number of mutant forms of an enzyme in a population varies widely from enzyme to enzyme. In most cases of pharmacogenetics, the reason for such enzyme differences is not clear. This is a striking fact, since the variability of drug-metabolizing enzymes often seems to have nonfunctional consequences in the absence of drugs. 

Pharmacogenetics involves the impact of genetic variation on drug response. The link between genetically determined variation in drug metabolism enzymes (e.g., cytochrome p450, N-acetyltransferase) and intersubject differences in pharmacokinetics is well established. Likewise, there is an increasing awareness that differences in transporter expression can impact the efficacy and safety of pharmacotherapy. 

It is self-evident that biotransformation will be reduced in patients with liver or kidney disease, in the elderly and also in neonates. In addition, pharmacogenetic differences play a considerable role in the way an individual patient metabolizes a drug. Such differences often result from polymorphisms in the cytochrome P450 family of microsomal enzymes. 

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