What to watch with CYP2D6 and Sport?

CYP2D6 is a key enzyme for metabolizing many drugs, including painkillers (codeine, tramadol) and beta-blockers used in sports. Depending on your genotype (poor, intermediate, normal, ultrarapid metabolizer), the same dose can have different effects or increase side effects. However, there is no strong evidence that CYP2D6 directly affects athletic performance, endurance, or recovery. Most claims linking CYP2D6 to sports are based on weak mechanistic reasoning or marketing. A DNA test can provide insight into drug metabolism, but it should not replace medical advice. Be cautious of products that label CYP2D6 as a 'fitness gene.' Evidence: unclear (no direct sport-related studies in the provided context).