You are correct in stating that narcan can throw an addict into withdrawal, which is not pleasant.
The "single use" one-time emergency kits cost $60 in my neighborhood pharmacy. The multiple-dose vial, which should be on hand in any facility that has addicts around I purchase for $17. Then you need a sub-cu needle, which can be purchased without prescription. The drug is not toxic and it is not possible to cause harm by injecting too much, except for inducing withdrawal symptoms. It has no effect whatsoever on heart rate or respirations.
It's an interesting drug. During the 1970's the U.S. Navy experimented with breaking the spines of cats and injecting them with Narcan. Surprisingly the cats recovered without paralysis. So they did a field study and injected narcan when the patients showed up at the ER. There was no evidence it helped prevent paralysis. I experimented injecting it into auto accident victims who had head flexure. What happens is amazing. THEY SELF SPLINT! In other words you don't need a collar (but we put them on). The head becomes rigid in position. When a person suffers trauma endorphins are released and they feel no pain. Sometimes you get a person with a severed arm and they are talklng to you like you were in a coffee shop. The narcan blocks the endorphins. You would think this fact would be well known, but every week we rediscover the wheel. Today paramedics do not have a protocol enabling them to inject narcan except for drug overdoses. The down side is the pain, but it is not always possible to apply axial traction and a proper collar to a patient in a crushed car who is rubber-necking. I would always use the narcan in these situations.
It's not the shelf-life. It's the half-life. I have injected a comatose heroin overdose who became completely normal. It took 25 minutes for him to crash, and that took about four minutes until complete unconsciousness again. It was like falling off a cliff. I managed to stay with him in his apartment watching television while he insisted he was "fine" and didn't need to go to the hospital. His weight was about 175 and the amount of opiates he injected is unknown. I timed the period until he again became unconscious., I gave him a second injection. THEN I took him to the ER. The drug has no real side effects. The problem is that the people become very normal. If injected into an addict, it may also cause withdrawal symptoms, to include cramps and pain. I keep a multi-dose vial around, which is very inexpensive, but requires a prescription. It was so cheap that until recently you didn't even have to sign for it. Decades ago, In the hospital it used to be scrounged because it will prolong an erection in a normal person by blocking the substances that cause blood to drain from the penis. The intramuscular route takes too long. We used to always inject it under the tongue. We did use it in an intravenous drip after the initial injection.
I'm glad you wrote on here that the Narcan has a short shelf life. I didn't know this and I was considering going and getting some to keep at our Wed night N/A mtg. People come in loaded all the time.....Not so sure now if that will work. How short is short?