There are a lot of drugs that contain >1 ingredients that work together. What makes you think it must be a poisoning conspiracy? The paracetamol+opiates combine

There are a lot of drugs that contain >1 ingredients that work together. What makes you think it must be a poisoning conspiracy? The paracetamol+opiates combined effect is widely documented in medical literature, and many of the most common painkillers are combinations of paractamol along with a mild optiate like codeine.