A female client starts a new prescription, oxybutynin, for symptoms of an overactive bladder. The client tells the nurse that she is training to run in a half-marathon. Which Instruction should the nurse emphasize?

A. Wear padding to protect from bruising if a fall occurs: While safety is important, oxybutynin, an anticholinergic medication used for overactive bladder, does not typically increase the risk of falls or bruising. Therefore, this instruction is less relevant to the specific concerns associated with taking oxybutynin. B. Avoid crowds to help prevent acquiring infections: Avoiding crowds can be a general precaution for various health conditions or treatments but is not specifically related to the use of oxybutynin. This medication does not have a significant impact on infection risk. C. Keep skin and eyes covered to protect from sun injury: While oxybutynin may cause some sensitivity to sunlight, it is not a primary concern compared to other side effects. The primary issue related to oxybutynin in the context of physical activity is managing hydration and body temperature. D. Take measures to avoid dehydration and over-heating: This is the most important instruction for a client taking oxybutynin, especially when training for a marathon. Oxybutynin can cause reduced sweating due to its anticholinergic effects, increasing the risk of dehydration and overheating. The nurse should emphasize the importance of staying hydrated and avoiding excessive heat to prevent complications during physical activity.