Final answer:
The enzyme absent in about 7% of Caucasians and 30% of East Africans is CYP2D6, which plays a critical role in drug metabolism. Poor metabolizers lacking this enzyme may need adjusted medication dosages for effective treatment.
Step-by-step explanation:
The CYP enzyme that is absent in approximately 7% of Caucasians and 30% of East Africans is CYP2D6. This specific cytochrome P450 enzyme is vital in the metabolism of many drugs. The genetic polymorphism in CYP2D6 can result in variations in drug metabolism among different populations, leading to drug inefficacy or adverse drug reactions in individuals who lack this enzyme.
Those who lack a functional CYP2D6 enzyme are often referred to as poor metabolizers, which means that they may not process certain medications as expected. This can be significant in clinical settings, as dose adjustments might be necessary for these individuals. The variability in CYP2D6 expression has implications for personalized medicine, as it is paramount to consider the patient's genotype when prescribing certain drugs.