Final answer:
Narcan, or naloxone, is not helpful for a ketamine overdose because ketamine is not an opioid.
Step-by-step explanation:
Naloxone, also known as Narcan, is an opioid antagonist that is commonly used as an antidote for opioid overdose. It works by quickly reversing the effects of opioids and restoring normal breathing. However, ketamine is not an opioid; it is a dissociative anesthetic. Therefore, Narcan would not be effective for a ketamine overdose.