Ottawa – How naloxone works? Naloxone (pronounced na-LOX-own) is a fast-acting medication used to temporarily reverse the effects of opioid overdoses, also called an opioid poisoning. Naloxone can begin to take effect within 2 minutes. If a response to an initial dose is not seen within 2-3 minutes, subsequent doses can safely be given. When you take an opioid, it …