Pharmaceutical Fentanyl comes as a solution for injection (Sublimaze), for transdermal delivery as a patch (Durogesic), as a tablet designed for buccal administration (Effentora) and as a nasal spray (PreFent). What is common here is that they are all designed for what is termed 'parenteral administration' which simply means not via the gastrointestinal tract. You cannot swallow fentanyl. Or rather you can, but it's bioavailability is described as 'sparse' in (chronic) studies i.e. it does not work, or at least not if one's liver is at all healthy. Fentanyl has an extremely short duration of action given that it's plasma half-life is about 18 minutes.
I won't bother you with the exact reasons for this, but I think what is important here is that whoever made this counterfeit pill relied on the user 'abusing' the pill i.e. by administering it via a parenteral route. As I understand it, imitation OxyContin makes up the bulk of these 'fakes'. Most users will crush and snort them. The serious problem here is that while oxycodone (the active drug in real OxyContin) is about twice as potent as morphine, fentanyl is around 80 times as potent. That means to approximate a 30mg OxyContin (for example), the maker of the fake would need to put less than 1mg of fentanyl into each pill.
While one might assume that these manufacturers would put the minimum amount of fentanyl into each tablet to maximise their own profit, the fact is that fentanyl is so incredibly cheap given it's potency, the trend is to put more in so that people develop tolerance and dependence. Needless to say, there is no quality control, no pharmacovigilance and given what they are doing, no concern for the end user whatsoever. They are sold by dubious pharmacists in Mexico and India. The buyer would not be aware that the medicine they purchased was fraudulent; they would not realise that they were dealing with a criminal.
The serum concentration for analgesia is around 1-2 ng/mL and around 10-20 ng/mL for anaesthesia. The latter dose regime is only used by specialists and only when mechanical ventilation and related life-support equipment is on hand. The mean concentration of fentanyl found in accidental overdose victims is 26.4 ng/mL (range 11.8-95.8 ng/mL).
I home you understand that my post is dispassionate in the attempt to provide you with the information that is useful to and understandable by you. All the data has been derived from multiple medical sources and is correct to the best of my knowledge. There are many different figures assigned to fentanyl. I think it is the order of magnitude that is important.
I have no idea under what circumstances this accident occurred so I cannot make any comments regarding this specific case. I merely wished to present what is available in textbooks, medical literature and such information as is made available to potential prescribers of medicines in which fentanyl is an active ingredient. There is a huge mythos surrounding ALL drugs but psychoactive drugs in particular and drugs of abuse specifically. Every case is unique and it is not useful to comment on specific cases.
If their is any indication as to who supplied these tablets, stopping them could be of great benefit to unwitting consumers. It goes without saying that there will almost certainly be many more of these fraudulent pills in circulation and that nobody knows if they have a pill that came from the same batch or even the same die (tablets are cast in dies, I am not making light of this terrible situation).