The greatest side effect of medications is that they often don't do what we expect them to do. Dr. Dan Roden, professor in the departments of medicine and pharmacology at Vanderbilt University School of Medicine, talks with Dr. Bruce Bloom about variability in response to drugs. Genetic components are just one of many reasons patients respond differently. Dr. Roden also discusses his specific work with customizing treatment for patients with arrhythmias based upon the disease mechanism.