Pharmacogenomics-based drug selection and dose adjustments help doctors to determine which medications are most likely to be effective or of no benefit to a patient due to impaired metabolic activity. The CYP2D6 enzyme function, for example, is of particular importance in selecting antidepressants causing moderate to severe side effects in 5-30% of people who take them due to their genetic make-up. Read More. In women treated with tamoxifen to reduce the risk of breast cancer development or recurrence, use of aromatase inhibitors is a reasonable alternative but the risk of osteoporosis may be increased in some patients. Read More.