A mixture of substances that may be lethal when combined and consumed. External factors like disease and genetics also play a role.
For example, having a medical history of heart disease and consuming drugs that thicken the blood and increase blood pressure is likely to cause a heart attack, making this lethal combination a suicide cocktail.
1: The toxicity report in his autopsy revealed that the heart attack was caused by large amounts of fentanyl, methamphetamine and cannabis found in his bloodstream.
2: That sounds like a suicide cocktail.