In addition to alcohol, benzodiazepines and the opiates (rare), another class of drugs that can cause lethal withdrawal symptoms is the barbiturates. In fact, they present the most dangerous withdrawal of all. Their use has largely been replaced with the benzodiazepines, so abuse is much less common today than it was in the 1960s and 1970s.
American Addiction Centers
The symptoms are
Stage 1: Anxiety, insomnia, nausea, and abdominal pain characterize
this stage, which begins 8 hours after the last drink.
Stage 2: High blood pressure, increased body temperature, unusual
heart rate, and confusion come with this stage, which begins 24-72
hours after the last drink.
Stage 3: Hallucinations, ...