[Pseudoscience-is-malarkey (OP)]

A common trope in movies, such as the Pet Semetery films, (when various undead characters suffer their second death from them) and even films reality based, is we see someone getting an injection (usually against their will) and falling to it's effects almost instantly. My understanding is that when giving someone a shot of morphine (which is the drug used in Pet Semetery) or any kind of drug, whether human or animals, it never takes effect instantly. With humans it must be about 10-15 minutes (longer and less effective if they have a tolerance?), with animals such as our dogs and cats, maybe 2-3?

I also don't understand how it can have any effect at all on the undead, as their blood is no longer operating. You even see this also happening to Jason Vorhees in Freddy vs Jason. And just like with Gage Creed and Churchill the cat in the Pet Semetery movie and book, it took effect almost instantly!

I recall a case involving a woman who was looked to have been brutally murdered. Her hands and feet were bound together behind her back. A black nylon stocking was tied tightly around her neck. Yet an autopsy revealed she died from an overdose of morphine. The head detective said there was no way that she could have been able, after ingesting that amount of drugs, to tie herself up. The coroner eventually intervened and concluded it was suicide, and that the woman, who had a long history of psychotic behavior, wanted it to look like she was murdered to send a powerful message to those that felt she was faking her behavior and filing false police reports, etc. The coroner also said the morphine wouldn’t have taken affect for 15-30 minutes. A knot specialist re-created the same type of knots and the way she was tied up, it took her three minutes.

[Hayseed]

Surely you jest.

[Bored chemist]

Define "shot".

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[chris]

The most significant determinant of the rate of onset of action of any drug is the route of administration. Drugs that target the nervous system, to effect changes in behaviour or conscious level, are usually small, volatile molecules that are highly lipophilic (like fat and dislike water). These properties make it easy for them to get across the blood brain barrier. The extent and rate of effect are therefore proportional to how quickly you can deliver the drug. An IV injection produces onset within seconds; intramuscular injection can be much slower but produce a more prolonged action. Smoking a cigarette delivers nicotine to the brain in seconds. Ditto sniffing or rubbing cocaine into the gum.

So, yes, "shots" can be effective very rapidly. But most anti-psychotics administered to calm down or sedate an agitated or confused patient (drugs like haloperidol) are given IM and have an onset over minutes. This doesn't make good telly, so they usually cheat.