You cannot become immune to Narcan because your body does not develop a tolerance to it. There's no limit or maximum number of Narcan doses that can be given to someone.

Narcan’s active chemical component is naloxone, which is an opioid antagonist. Opioids, like heroin or OxyCodone, are opioid agonists which means that they will bind to the opioid receptors in your brain producing pleasure and numbing pain. Because opioid agonists replace the naturally occurring opioids that stimulate reward circuitry in your brain, they can become addictive and your body can build up a tolerance to them. Narcan, on the other hand, is an opioid antagonist. This means it binds to the opioid receptors in your brain. It only functions to block other opioids from affecting your body.