Over the weekend FOX aired Part 3 of a documentary on Marilyn Monroe. It's of interest here because of the enema references.
In summary they reported that Marilyn had been taking meds during the day of her death and apparently couldn't sleep.
So the doctor(s) ordered a dose Chloral Hydrate. A lookup on the web indicates the dosage is around 500mg.
In the show, there is a red combination syringe being filled in a sink.
Also the announcer said that the autopsy said she was full of poo, so the drug could not have been administered by enema.
IMO, this is utter nonsense. A small quantity of a drug would not have been given in a large volume enema.
The desired result was for the drug be absorbed and the patient sedated, not be made to poo.
That's not going to happen with a bag full of water because the enema will provoke a prompt poo, passing out the drug as well.
It is much more likely, IMO, that the drug was given in a small volume enema, with a bulb or piston syringe of a very few ounce capacity.
Such an enema does not have a strong laxative effect.
Hence, the post mortem report contained nonsense. My opinion, FWIW.