"What if the drink cups were exchanged by accident and Daniel mistakenly took ANS drink and drugs?"
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That was my direction as "Devil's Advocate"
Especially since I clearly heard Dr. Michael Barden the other celebrity pathologist make the statement that liquid methodone is taken orally in orange juice.
Remember that ANS did not have pills in her stomach - and I don't know about Daniel.
With respect to the lack of pills in ANS' stomach - drugs can be more effectively administered in pessaries or suppositories - they enter the blood stream and vomiting from the stomach is avoided.
It has always been speculated that is how the drugs that killed Marilyn Monroe was administered... by suppository or enema, it does get into the blood stream more quickly and is harder to detect. One reason why if you are dehydrated (or even a pet) you can hydrate by giving a solution by enema.