“Taken alone antihistamines are difficult to die from”
However, they were mixed with fentanyl and alcohol:
https://www.therecoveryvillage.com/fentanyl-addiction/faq/mixing-fentanyl-alcohol/
It’s the alcohol
I’ve had fentanyl and phenergan for trauma and heart surgeries
It’s also the two second ingredients in epidurals for delivery
After lidocaine or whatever Caine
Fentanyl or any opioid with phenergan is routine
No question it enhances the opiate but it’s not lethal unless enormous lab rat smokes 2000 joints a day test or booze etc is mixed in
https://www.drugs.com/drug-interactions/droperidol-fentanyl-with-phenergan-945-0-1949-1259.html