On rare occasions, sudden death can occur on the first use of cocaine or unexpectedly thereafter. However, there is no way to determine who is prone to sudden death.
With the long term use of methadone some users may eventually develop respiratory issues, heart problems and liver and kidney problems which can turn into chronic and deadly conditions due to methadone addiction.
Some of the worst prescription drug withdrawal symptoms documented are from the drug Cymbalta, which are sometimes referred to as "nightmare-ish" due to their intensity and prevalence.
The human liver combines cocaine and alcohol to produce a third substance, cocaethylene, which intensifies the effects of the drug. Cocaethylene is associated with a greater risk of sudden death than just crack cocaine.